An Investigation for Developing Local Industry and Formulation of Mathematical Relationships

Amna Yagoub Osman Ibrahim

M.Sc. in Textile Technology, Department of Textile Engineering, Faculty of Science and Technology, University of Gezira, (1996)

A Thesis Submitted to the University of Gezira in Fulfillment of the Doctor of Philosophy in Textile Engineering Technology

Department of Textile Engineering

Faculty of Textiles

November /2013onth/Year

i

Investigation for Developing Local Knitting Industry and

Formulation of Mathematical Relationships

By: Amna Yagoub Osman Ibrahim

Supervision Committee:

Name Position Signature

Prof. Dr. Eng. Abbass Yousif Abu Salma Main Supervisor ………

Dr. Fadl Elmoula Abdallah Idris Co-supervisor ......

...... … ……………… Co-supervisor ………

Date of Examination: November /2013

ii

Investigation for Developing Local Knitting Industry and Formulation of Mathematical Relationships

By: Amna Yagoub Osman Ibrahim

Examination Committee:

Name Position Signature

……………………………. Chair Person ………………...

...... External Examiner ………………...

...... Internal Examiner …………………

Date of Examination: November /2013

iii

Dedication

Dedicated to my dear parents, family & friends

iv

Acknowledgements

First I thank Allah for giving me ability to do this study. All majesty words to Prof. Dr. Eng. Abbass Yousif Abu Salma for his support and continuous supervision. I would like to express my sincere thanks to Dr Eng. Fadl Elmoula Abd Allah Idris the co-supervisor for his support. My particular thanks are to Syed Eng. Eltigany Mohamed Abd Allah the manager of Elhashmab factory, who assisted me for collection and giving me permission to carry this study in Elhashmab factory. Also thanks are due to Syed Adil Ibrahim and Miss Amna Karrar, the staff of the textile engineering laboratory-Sudan University for Science and Technology for their great help, and to the staff of Faculty of Textiles - University of Gezira. Many thanks are to my family and all who supported this study.

v

An Investigation for Developing Local Knitting Industry and Formulation

of Mathematical Relationships By: AmnaYagoub Osman Ibrahim Degree of Doctor of Philosophy Textile Engineering Technology (2013) Department of Textile Engineering, Faculty of Textiles, University of Gezira M.Sc. in Textile Technology University of Gezira, Faculty of Science and Technology (1996)

Abstract Knitting industry was developed and made a competition for the industry in many areas .The growing development has not found its way-out to the local knitting industry. Visiting to the local knitting factories showed that there was deficiency in solving such problems. The purpose of this study was to investigate knitting parameters and to formulate mathematical relationships. This was based on scientific and engineering approaches to achieve better knitting performance. A survey of local industry was carried out. It was found that, factories did not possess measuring instruments for measuring tension; they rely on manual control which is subjected to mistakes. Beside problems encountered, are poor machine settings, particularly adjusting of loop length, tension control, and procurement of needles…etc. The experimental work was carried out in El Hashmab knitting factory, located in Omdurman. The bulk of the experimental work was carried out in a circular Terrot machine, having a diameter of 17″ and its was 12. The initial machine setting had been checked before producing the required fabric samples. Producing fabric samples with different parameters was confronted with problems of yarn procurement according to required specifications, from local mills .Yarns were subjected to physical tests; the fabrics produced were tested in the Textile Engineering laboratory -Department of Textile Engineering- Sudan University of Science and Technology, the results were tabulated and analyzed. The impact of increasing the machine speed on yarn input tension was also investigated. The main findings of this work were represented in mathematical relationships relating to yarn count, loop length, yarn tension and waxing in order to achieve better knitting performance. These relationships will help in manufacturing knitted fabrics with regular engineered structure which conform to the market requirements. A slight in tension was found during high speeds but within the permitted limits. The measuring device for determining yarn tension helped in improving fabric quality due to accurate measurement of tension. More investigations are required to study the effect of yarn waxing in local knitting manufacture as well as the impact of very high speed on yarn input tension.

vi

المحلية وصياغة معادالت رياضية دراسة لتطوير صناعة التريكو

إعداد الطالبة: آمنة عثمان يعقوب إبراهيم

مستخلص تطورت صناعة التريكو وأصبحت منافسة لصناعة النسيج في مجاالت كثيرة. هذا التطور المهم لصناعة التريكو لم يجد طريقه للصناعة المحلية وأن هناك صعوبات تواجه تطور هذه الصناعة. أظهرت الزيارات إلي مصانع التريكو المحلية نقصا وقصورا في إيجاد حلول لبعض هذه المشاكل. الغرض من هذه الدراسة تحديد معلمات التريكو المناسبة وصياغة عالقات رياضية لالستجابة السريعة لعملية التريكو. فى هذا االطار تم اجراء مسح لمتطلبات العمالء. و يستند هذا على النهج العلمي و الهندسي للوصول لألداء االفضل من نتائج المسح أن كل المصانع لم تتوفربها أجهزة قياس شدد الخيط وأنهم يعتمدون على الضبط اليدوي وهو شامل لمصانع التريكو المحلية. ظهر معرض لالخطاء. ايضا المشاكل التي واجهت المصنعين تمثلت في ضعف ضبط ماكينة التريكو ال سيما ضبط طول العروة و قوة الشد وايضا اإلبر. تم تنفيذ الجزء العملي لهذه الدراسة بمصنع الهاشماب بامدرمان. وتم تنفيذ الجزء األكبر من العمل التجريبي بماكينة تريكو لحمة دائرية لقد تمت مراجعة الضبط االبتدائي للماكينة قبل استخدامها النتاج عينات األقمشة المطلوبة. واجه انتاج (.Terrotقطرها 17 بوصة عيار 12 ) عينات البحث بمعلمات مختلفة مشاكل في توفير الخيوط بالمواصفات المطلوبة تم جلبها من المصانع المحلية وتم انتاج عينات من قماش التريكو مع معلمات مختلفة. تم اختبار الخيط واألقمشة المنتجة في معمل قسم هندسة النسيج - جامعة السودان للعلوم والتكنولوجيا. تمثلت النتائج الرئيسة لهذا البحث في العالقات الرياضية المتعلقة بطول العروة ونمرة الخيط وقوة الشد وسرعة الماكينة وتشميع الخيط من أجل تحقيق أفضل أداء للتريكو. هذه المعادالت تعين فى تصنيع أقمشة تريكو ذات بناء هندسي سليم ومنتظم. لوحظ ان قوة الشد)سنت نيوتن( تزداد مع انسياب الخيط من بكرة الخيط وعند المغذيات ألعلى قيمة لها في منطقة صنع العرو لكل من الخيوط المشمعة وغير المشمعة. فى اطار هذا البحث ايضا تمت دراسة أثر زيادة سرعة الماكينة على قوة الشد )سنت نيوتن( فى منطقة صنع العرو وجدت زيادة طفيفة فى قوة الشد اثناء السرعات العالية وايضا تسهل سرعة االستجابة للسوق وفق مواصفات األقمشة المطلوبة. وقد وضح ان استخدام جهاز قياس الشدد إال أنها فى الحدود المسموح بها. القماش المنتج وذلك لدقة تحديد قوة الشد. لذا يلزم نصح المصنعين المحليين بالحصول على أجهزة قياس قوة الشد له أثر مباشر في تحسين جودة للتحكم في الشدد على الخيط. ويلزم المزيد من التحقيقات لمعرفة تأثير تشميع الخيط علي كفاءة صناعة التريكو المحلية، فضال عن تأثير السرعة العالية جدا على زيادة شدد الخيط .

- 7 -

Table of contents Title Page Dedication iii Acknowledgements iv Abstract (Eng.) v Abstract (Arabic) vi Table of contents vii List of tables x List of figures xii Chapter one: Introduction 1.1 General introduction 1 1.2 Problem identification and Justification 3 1.3 Objectives 4 Chapter Two: Literature review 2.1 technology 5 2.2 5 2.3 Manual frame 5 2.3.1 Principle of the manual frame 6 2.3.2 Improvement of the manual frame 8 2.4 Powered 9 2.5 High speed knitting machines 11 2.6 Electronic knitting machines 12 2.7 Advances in knitting technology 13 2.8 Factors determining economy and productivity of a knitting factory 14 2.9 knitting mechanism 14 2.9.1 Types of knitting machines 15 2.9.2 Local knitting machines 15 2.9.3 Weft knitting machine general feature 15 2.9.3.1 Knitting elements 16 2.9.3.1.1 Needles 16 2.9.3.1.1.1 Bearded needle 17 2.9.3.1.1.2 Latch needle 18 2.9.3.1.1.3 Compound needle 18 2.9.3.1.2 The holding down – knock over 19 2.9.3.1.3 Sinkers 19 2.9.3.1.4 The needle carriers (needle cylinder, needle dial) 20 2.9.3.1.5 Cams 20 2.9.3.1.5.1 Engineering cams 20 2.9.3.1.5.2 Knitting cams 21 2.9.3.2 Knitting cycle 22 2.9.3.2.1 Knitting cycle of latch needle 22 2.10 24 2.11 Optimizing knitting performance and fabric quality 25 Chapter Three: Materials, method and equipment 3.1 Materials 29 3.2 Methods 30 3.2.1 Introduction 30 3.2.2 Survey of the local knitting industry 31 3.2.2.1 2. Primary data31 3.2.2.2 Layout and machinery arrangement 31 3.2.2.3 Activities 31

- 8 - 3.2.2.4 Technology and types of installed machinery 31 3.2.2.5 Type of yarns used 31 3.2.2.6 Type of products and production efficiency 31 3.2.2.7 Operating conditions and cleaning efficiency 31 3.2.3 Investigation of the knitting parameters 32 3.2.3.1 Investigation of effect of initial machine setting on performance 35 3.2.3. 1.1 Production of knitted rib fabrics by initial & adjusted setting 32 3.2.3.1.2 Fabric quality tests 32 3.2.3.2 Investigation of effect of varying loop length 34 3.2.3.2.1 Productions of fabric samples by varying loop length 35 3.2.3.2.2 Fabric quality tests 35 3.2.3.3 Investigating of effect of yarn count (Ne) 35 3.2.3.3.1 Production of fabric samples by varying yarn count 36 3.2.3.3.2 Fabric quality tests 36 3.2.3.4 Investigating of yarn waxing on knitting performance 36 3.2.3.4.1 Measurement of tension build-up at different zone 36 3.2.3.4.2 Production of fabric samples by waxed & un- waxed yarn 37 3.2.3.4.3 Fabric quality test 37 3.2.3.5 Investigating of machine speed on knitting performance 37 3.2.3.5.1 Measurement of tension (cN) build-up at knitting zone 37 3.2.3.5.2 Rate of breakage 37 3.3 Statistical analysis 38 3.4 Equipment 40 3.4.1 Machine used 40 3.4.2 Measuring Devices 40 Chapter Four: Results and discussion 4.1 Result of the survey of local knitting industry 46 4.1.1 Primary data 46 4.1.2 Local knitting factories layout and machinery arrangement 47 4.1.3 Activities 48 4.1.4 Technology and types of installed machinery 49 4.1.4.1 Technology of installed machinery 49 4.1.4.2 Types of machineries installed on local knitting sector 50 4.1.5 Type of yarns used 51 4.1.6 Type of products and production efficiency 52 4.1.6.1 Type of products 52 4.1.6.2 Production efficiency 53 4.1.7 Operating conditions and cleaning efficiency 54 4.1.7.1 Operating conditions 54 4.1.7.2 Cleaning efficiency 55 4.2 Results of investigation of knitting parameters 57 4.2.1 Results of investigation of effect of initial machine setting - terrot 57 4.2.1. 1 Measured results of loop length and tension level at all feeders 57 4.2.1. 2 Results of fabric quality tests for initial & adjusted machine setting 58 4.2.1. 2. 1 Fabric structure for barakat (a) and acala (b) cotton yarn 58 4.2.1. 2. 2 Results of fabric width and shrinkage for barakat and acala cotton yarns 63 4.2.1. 2. 3 Measurement of fabric gsm for barakat and acala cotton yarns 66

- 9 - 4.2.1. 2. 4 Fabric extensibility for barakat and acala cotton yarns 69 4.2.1.2. 5 Results of fabric pilling for barakat and acala cotton yarns 72 4.2.2 Investigation of adjusted different loop lengths 73 4.2.2. 1 Results of fabric quality tests 73 4.2.2. 1.1 Fabric structure 73 4.2.2. 1.2 Fabric width 75 4.2.2. 1.3 Fabric weight per square meter 77 4.2.2. 1.4 Fabric extensibility % 79 4.2.3 Investigation of different yarn counts on knitting performance 81 4.2.3. 1 Results of fabric quality tests 81 4.2.3. 1.1 Fabric structure 81 4.2.3. 1.2 Fabric width 83 4.2.3. 1.3 Fabric weights in grams per square meter 85 4.2.3. 1.4 Fabric extensibility % 87 4.2.4 Investigation of effect of yarn waxing in knitting performance 90 4.2.4.1 Tension build-up during operation 90 4.2.4.2 Fabric abrasions by using waxed and un-waxed yarns 92 4.2.5 Investigation of knitting machine speed on knitting performance 94 List of 4.2.5.1 Result of measurement of tension levels at knitting zone 94 4.2.5.2 Rate of breakage with increasing speed 95 Tables Chapter Five: Conclusion and Recommendations 5.1 Conclusion 96 5.2 Recommendations 97 6. References 98 List of Tables Page 3.1 Yarn quality 29 4.1 Primary data about local knitting industry 46 4.2 Measured space between machines and walls in knitting room 48 4.3 Type of activities in local knitting sector 49 4.4 Type of technologies in local knitting sector 50 4.5 Types of machineries installed in local knitting sector 51 4.6 Types of yarn counts used in local knitting factories 51 4.7 Type of knitted goods produced in local knitting factories 52 4.8 Actual production of knitted goods in local industry 54 4.9 Type of facilities used in conditioning local knitting rooms 55 4.10 Cleaning efficiency of local knitting factories 56 4.11 Initial readings of loop lengths & tension levels at different feeders 57 4.12 Measurements of fabric wales/cm (initial & adjusted setting, barakat) 58 4.13 Paired test for fabric wales/cm (initial & adjusted setting, barakat) 59 4.14 Measurements of fabric courses/cm (initial & adjusted setting, barakat) 59 4.15 Paired test for fabric courses/cm (initial & adjusted setting ,barakat) 60 4.16 Results of fabric wales/cm (initial & adjusted setting, acala) 61 4.17 Paired test for fabric wales /cm (initial & adjusted setting, acala) 61 4.18 Measurements of fabric courses/cm (initial & adjusted setting, acala) 62 4.19 Paired test for fabric courses/cm (initial & adjusted setting, acala) 62 4.20 Results of fabrics width & shrinkage (initial & adjusted setting, barakat) 63 4.21 Paired test for fabric width and shrinkage (initial & adjusted setting, barakat) 64 4.22 Results of fabric width and shrinkage (initial & adjusted setting, acala) 65 4.23 Paired test for fabric width and shrinkage (initial & adjusted setting, acala) 66

- 10 - 4.24 Results of fabric gm/sqm (initial & adjusted setting, barakat) 66 4.25 Paired test for fabric gm/sqm (initial & adjusted setting, barakat) 67 4.26 Results of fabric gm/sqm (initial & adjusted setting, acala) 68 4.27 Paired samples test for fabric gm/sqm (initial & adjusted setting, acala) 68 4.28 Results of fabric extensibility % for fabric (initial & adjusted setting, barakat) 69 4.29 Paired test for fabric extensibility %(initial & adjusted setting ,barakat) 70 4.30 Measurements of fabric extensibility % (initial & adjusted setting, acala) 71 4.31 Paired test for fabric extensibility % (initial & adjusted setting, acala) 72 4.32 Measurement of fabric structure by varying loop length for barakat cotton yarn Ne 36 73 4.33 Correlation test of w/cm & c/cm against loop length for yarn Ne.36 74 4.34 Regression coefficients for wales &courses /cm by varying loop length 75 4.35 Measurement of fabric width produced by varying loop lengths 75 4.36 Correlation test for fabric width and loop length, barakat yarn Ne.36 76 4.37 Regression coefficients for fabric width & shrink against loop length 77 4.38 Measurement of fabric gms by different loop lengths 77 4.39 Correlation test for gm/sqm and loop length, barakat cotton yarn Ne.36 78 4.40 Regression coefficients of fabric weight/sqm against loop length 78 4.41 Measurements of fabric extension and recovery by varying loop length 79 4.42 Correlations test for extension and recovery against loop length 79 4.43 Regression coefficients for fabric extension and recovery against loop length 80 4.44 Results of fabric structure by different yarn counts 81 4.45 Correlation test for fabric structure vs. yarn count Ne. 36, 30 & 24 82 4.46 Regression coefficient of fabric structure against yarn count Ne.36, 30,24 83 4.47 Measurement of fabric width cm a against yarn counts Ne 83 4.48 C Correlations test for fabric width vs. yarn count Ne: 36, 30 & 2484 4.49 Regression test for fabric width against yarns count Ne:36, 30, 24 85 4.50 Results of fabric gms for different yarn counts Ne 85 4.51 Correlation test for fabric weight against yarn count Ne:36, 30, 24 86 4.52 Regression test for fabric weight against yarn count Ne:36, 30, 24 86 4.53 Results of fabric extension for different yarn counts Ne: 36, 30 and 24 87 4.54 Correlation test for fabric extension against yarn count 88 4.55 Regression test for fabric extension against yarn count 88 4.56 Tension build-up by using waxed and un-waxed barakat cotton yarn Ne 20 At different zones in knitting machine 90 4.57 Ave. tension cN build-up by using waxed and un-waxed yarn Ne 20/1 91 4.58 Pair test for tension build-up by waxed and un-waxed yarn & machine elements 92 4.59 Gm/sqm of abraded fabrics by waxed and un-waxed yarn Ne 20/1 92 4.60 R Results of abrade weights gms for fabric made from waxed and un-waxed92 4.61 Pair test for abraded waxed un-waxed 93 4.62 Measurement of tension cN at knitting zones for various operating speeds 94 4.63 Correlation test for tension cN at knitting zone by increasing operating speed 95 4.64 Ave. results of yarn breakages per hour for various operating speeds 95 4.65 Correlation test for rate of breakage against increasing machine speed 95

- 11 - List of figures List of figures page 1.1 Flow chart textile manufacturing processes 1 1.2 Basic knitted structure 2 2.1 General view of knitting frame 6 2.2 Side view of Lee frame 7 2.3 View of manual frame 7 2.4 William Lee’s steps for knitting action 8 2.5 Derby rib technique 9 2.6 View of radial arrangements of needles 10 2.7 Hand-operated frame 11 2.8 First Mayer and Cie circular Knitting machine 12 2.9 Electronic sampling knitting machine 13 2.10 Exchangeable cylinder-dials from Mayer & Coe 14 2.11 Knitting machine organization chart 15 2.12 Bearded needle and its parts 17 2.13 Latch needle and its parts 18 2.14 Compound needle and its parts 18 2.15 A sinker between two adjacent needles 19 2.16 Different sinker constructions 20 2.17 Knitting cams triangle 21 2.18 Knitting cycle of latch needle 24 2.19 Plain kitted fabric 24 2.20 Rib knitted fabric 25 2.21 Purl fabric 25 2.22 Interlock knitted fabric 25 3.1 Side view stitch length measuring device, the scale 34 3.2 Top view of stitch length measuring device, the scale 35 3.3 Zones where tension was determined for the effect yarn waxing 37 3.4 Terrot double knitting machine 40 3.5 Hygrometer 41 3.6 Yarn tension meter 42 3.7a Fryma Fabric Extensiometer 43 3.7b Fryma Fabric Extensiometer 43 3.8 Abrasion resistance tester 44 3.9 Electronic balance 45 3.10 Fabric magnifying glass 45 4.1 Geographical locations of local knitting factories 47 4.2 Allowable space for worker movement in side knitting hose 48 4.3 Type of activities in knitting sector 49 4.4 Type technologies in local knitting sector 50 4.5 Types of machinery installed in local knitting industry 51 3.6 Type of yarn counts (Ne) used in local knitting factories 52 4.7 Type of knitted goods produced on local knitting factories 53 4.8 Available facilities used in conditioning knitting room 55 4.9 Wales/cm vs. serial meter for initial & adjusted setting , barakat 59 4.10 Courses/cm vs. serial meter for initial & adjusted setting , baraat 60 4.11 Wales/cm vs. serial meter for initial & adjusted setting , acala61 4.12 Courses/cm vs. serial meter for initial & adjusted setting , acala 62 4.13 Fabric width vs. serial meter for initial & adjusted setting , barakat 64 4.14 Fabric width vs. serial meter for initial & adjusted setting , acala 65 4.15 Gm/sqm vs serial meter for initial & adjusted setting , barakat 67

- 12 - 4.16 Gm/sqm vs. serial meter for initial & adjusted setting , acala 68 4.17a Fabric extensibility vs.sm for initial & adjusted setting, barakat 70 4.17 b Fabric recovery vs.sm for initial & adjusted setting, barakat 70 4.18 a Fabric extensibility vs. sm for initial & adjusted setting , acala (extension %) 71 4.18 b Fabric extensibility vs. sm for initial & adjusted setting, acala (recovery %) 71 4.19 a Effect of loop length on wales/cm for barakat cotton yarn 74 4.19 b Effect of loop length on courses/cm for barakat cotton yarn 74 4.20 a Effect of loop length on fabric shrink for barakat cotton yarn 76 4.20 b Effect of loop length on fabric width for barakat cotton yarn 76 4.21 Effect of varying loop length on fabric weight for barakat cotton yarn Ne.36 /1 78 4.22 Effect of loop length on fabric extensibility 80 4.23 a Effect of different yarn counts on fabric structure (courses/cm) 82 4.23 b Effect of different yarn counts on fabric structure (wales/cm) 82 4.24 Effect of yarn count Ne on fabric width 84 4.25 Effect of yarn count Ne on fabric weight gm/sqm 86 4.26 a Effect of yarn count Ne on fabric extension 88 4.26 b Effect of yarn count Ne on fabric recovery 88 4.27 Average tension levels in cN for waxed and un-waxed cotton yarn 93 4.28 Weight of abraded knitted fabrics against abrading cycles 91 4.29 Tension build-up during increasing knitting machine speed 95

- 13 - Chapter One:

Introduction

- 14 - 1.1 General introduction:

Textile industry is one of the most complicated manufacturing industries constitute many activities such as production of fibers, yarn, fabric ….etc. Following is a flow chart of the different processes involved in this sector as shown in Figure 1.1.

Textile Processing

Processing Input Steps Output

yarn Manufacturing Raw Yarn material/fibers (Spinning Mill)

Grey fabric Fabric Manufacturing Gray fabric Yarn (Weaving/Knitting Industry)

Wet Processing Finished Grey Fabrics Fabrics (Dyeing, Printing & Finishing Industry)

Finished Garment Manufacturing Garments Fabrics Garment Industry

Figure 1.1: Flow chart of the textile manufacturing processes

Conversion of yarn to fabric can be done by two common methods namely weaving by loom and knitting-by-knitting machine. There is a great difference between the geometry of the fabric manufactured by each method. Weaving is the name given to the interlacing of two sets of yarns, warp and weft at right angles and the fabric thus formed is woven fabric. Knitting is the construction of the fabric by forming the yarn into loops, which hang upon the other. Knitting was practiced historically on a small scale by individuals and was eventually developed with the lapse of time to a well– established industry. It is today competitive with the weaving technology. This growing importance of the knitting industry has not found much way to the local knitting industry. A modern weft-knitting machine today can produce up to

- 15 - half a ton of fabrics, whereas the local weft knitting industry is far behind this level, as a knitting machine produces in average not more than 20 kg of fabrics per day. The quality of knitting fabrics is today internationally very important to any endues be that apparel use of male, female and children; Community segments or industrial use in medical field or in other applications. There are many important contributory factors, which determine the productivity of a circular knitting machine. However, these factors depend on the geographical region (Mayer & Cie, 2007), subject to the availability of trained staff, suitable materials, and good base of infrastructure. This study is concerned with local knitting industry. The term quality, in knitting manufacture, is sometimes used, when referring to wales and courses per inch or centimeter, either in knitted or finished relaxed state (David, 2001). The wales and courses constitute the knitted fabric structure when they are meshed together at right angles. The basic need in quality is to engineer the product; it means that specifications are prepared which set up standards and dimensions that can easily be checked on the factory floor (Harry, 1964). Fortunately, the unique properties of knitted construction consist of two very important features. First, the ability to be engineered to produce different shapes and articles. By this potential, it could respond rapidly to requirements in non-apparel areas. Second, the knitted technology in its known application is to provide traditional shapes, sweaters, hosiery, jersey and outerwear and other tricot fabrics. Figure 1.2 shows a basic knitted structure.

Wale

Course

Figure 1.2: Basic knitted structures

- 16 - 1.2 Problem Identification and Justification:

Visiting some local knitting industries showed a certain negligence and deficiency in solving problems. It was noticed that at least one knitting machine was out of production for two years just because of poor ground leveling, which is a weak argument. This factory has lost a lot of money for trying to repair and reassemble the machine without success. Local knitting manufacturers suffer from problems such as poor machine settings, poor maintenance and lack of technical knowledge I want to draw a attention to the following facts. 1/ The main problem is adjustment of the loop length to produce fabrics with correct stitches. 2/ The problem of the low quality yarns procured from yarns originated in the local market. 3/ Difficulties in choosing suitable yarn count for particular machine setting. 4/ Domestic manufacturers suffer from the high quality of the imported goods and the strong competition accordingly. 5/ Difficulties in changing the initial machine setting to suit a particular customer requirement The above-mentioned problems constitute a basis for developing the local knitting industry. This research study has the objective of trials of setting scientific and technological basis to contribute in the development of the local industry. Investigating such problems necessitated survey of the local knitting industry with the objective of trying to solve problems. The owners, from the start, did not check and control machinery arrangement and layout; this created problem of internal transport and lack of production flow. Dimensional stability and loop length affect other mutually. The loop lengths depend on machine setting and yarn tension level. The fabric dimensions, on the hand are influenced by wales and courses per centimeter, wales are formed from the vertical loops, were as courses consist of horizontal loops. Many studies had been done in the area of improving quality; for example identification of faults, defining causes of yarn tension. Other studies specialized in adding devices to monitor the knitting process. There are some known studies to identify fabrics with special characteristics. Examples of such studies are mentioned in chapter one of this research.

- 17 - 1.3 Objectives:

This research work is the investigation of knitting parameters and achieving the optimum of quality and performance. Knitting parameters include some, but not all items such as machine speed, structural properties of fabric i.e. courses and wales per cm, stitch length and machine settings. Fabric testing will be made and matched with machine performance. This study aims for setting mathematical and physical formulae by using different fibers and yarns in order to produce the optimum fabric quality. The study aims to help local knitting manufacturers to gain experience in quick response and just in time delivery by generating knowledge about interaction of material and machine setting. Investigating of initial machine setting, loop length and tension to achieve the proper scientific levels of knitting performance.

- 18 - Chapter Two:

Literature review

- 19 - 2.1 History of knitting technology:

Knitting is an old method of making fabrics, it dates back to the pre-Christian era (Harry,1964 ; Doric Public company, 1972).The term knitting describes the technique of constructing textile structures by forming a continuous length of yarn into columns of vertically intermeshed loops, (David, 2001).

2.2 Hand knitting:

Some important finds have been made in Egypt, which indicates that advanced hand knitting methods were well known in the fifth century A.D, (Harry,1964; Nadia, 2004). The Egyptologist Society has fixed the date as the fifth century A.D (Doric Public company, 1972 ; David, 2001). However, knitting was apparently unknown in Europe before the 15th cent, (High-Beam Encyclopedia, 2005). Knitting was introduced into Europe by the Arabs and flourished in England and Scotland in about the fifteenth century, (Doric Public company, 1972; Microsoft Corporation, 2000). Hand knitting in England expanded as an industry in Tudor times (1485-1603). By the time of Elizabeth I, knowledge of how to hand-knit stockings had spread around England and documents refer to the industry in places as far apart as London, Kingston (Surrey), and Richmond, (Knitting Together, 2002). The principle of hand knitting was based on using two pins and a man can produce one loop at a time, (Thomson, 2005). A skilled hand-knitter produces about 120 stitches per minute, (Meisenbach, 1995) the hand knitting, which is today popular and a useful activity led the way to mechanical stitch formation, (Meisenbach, 1995) i.e. creation of manual frame.

2.3 Manual frame:

The manual frame (knitting machine) was invented by an English man named William Lee at about 1589, during the reign of Queen Elizabeth 1, (Manchester M.Sc. Lectures, 2007, Cooper, 1991 and Negley,1989) .This first manual frame, which is also known as frame work knitting, could knit stockings (High-Beam Encyclopedia ,2005 and Manchester M.Sc. Lectures, 2007). It is also known as Lee frame (Harry, 1964, Doric Public company, 1972 and

- 20 - Meisenbach, 1995) as shown Fig.2.1. The frame allowed production of a complete row of loops at one time unlike hand knitting which allows only one loop at a time, (Cooper, 1991). Lee presented his invention to Elizabeth 1, requesting a royal grant to exploit the device, (Thomson, 2005 ; Ian,1995).

Figure 2.1: General view of William Lee knitting frame

Queen Elizabeth I refused William Lee’s patent for two reasons. The new invention was seen as a threat to many of the hand knitters in the country, which might lead them losing work. The other reason is that the Lee’s frame knitted poor quality woolen stockings, (David 2001 ; Cooper, 1991).The Lee’s first frame greatly increased the speed of the knitting process and produced around 600 loops per minute compared with a hand-knitter’s 100 loops per minute, (Knitting Together, 2002 ; David, 2001).

2.3.1 Principle of the manual frame:

Figure 2.2 shows side view of lee frame mechanism. Jack sinkers were placed between the needles, which cases the yarn to form loops. The jack sinkers were hung from pivoted levers known as jacks. Springs locked onto the back end of the jack and held them in place until a metal block (known as slurcok) was pulled along a carriage to knock the springs back and release the jacks. Two pedals pulled the slurcock from side to side. Once the sinkers had dropped, they were used to bring the partially formed loops forward and under the hooks of the needles, the sinkers were then used to bring the old course of loops over the closed hooks. A locker bar then pushed the jacks back under the springs to lock them in place ready for a new yarn to be laid, (David, 2001; Knitting Together, 2002).

- 21 -

Bearded Needle

Figure 2.2: Side view of Lee frame

The knitting process started with the framework knitter laying a yarn C across a horizontal row of hooked needles B as shown in Figure 2.3. The principle is clearly shown in Figure 2.4 steps one to five, (Classic Encyclopedia, 1911).

A= needle bed

B=bearded needles

C=loops at the needle hook

D=fabric

Figure 2.3: General view of manual frame

- 22 - Step 1: Step 2: The yarn is put on Clinking the yarn the needle stem around needles

Step 3: Step 4 : Moving the new Pressing the loops to inside the needle beards and needle beards moving old loops over them

Step 5: Knock-over and forming the fabric

Figure 2.4: William Lee’s steps for knitting action

2.3.2 Improvement of the manual frame:

In 1596, Lee developed his frame to a finer gauge of 20 needles per inch instead of eight needles per inch. The new frame is capable of knitting fine silk yarns, where only course wool yarns can be knitted by the old frame, (Doric Public company, 1972; David, 2001 and Ian, 1991). Several knitting frames were developed after the Lee frame, William Lee himself and his brother James took their developed nine machines and knitters to France at the invitation of Henry IV in 1609, (David, 2001 ; Cooper, 1991). Lee set up a workshop in Rouen and signed a partnership agreement with Pierre de Caux in 1611, to provide knitting machines for the manufacturer of silk and wool, (David, 2001). It was believed that during this time, Lee died and his brother brought most of the machines and knitters back to London, (David, 2001). England then prohibited the export of stocking frames, but hundred of accurate drawings and availed knowledge enabled frames to be built in Paris from 1656 onwards. The knowledge of their operation spread across Europe, (David, 2001; Knitting Together, 2002). However,

- 23 - gradually London became CENTER of knitting frames and by 1750 the major areas could be broadly classified as Derby for silk Nottingham for cotton and Leicester for wool knitting, (David, 2001; Thomson, 2005). Not until 1750 were frame knitted stockings accepted as comparable in quality to those hand knitted with pins, (David, 2001).The improved versions of the frame used for knitting silk stockings formed around 1000-1500 loops per minute, (David, 2001; Knitting Together, 2002). In 1758, Jedediah Strutt developed a device, which would produce in knit cloths (double knit technique), (Doric Public company, 1972; David, 2001; Microsoft Corporation, 2000; Meisenbach, 1995). This invention refers to an attachment for the hand-knitting frame, which became world famous under the name: derby rib machine (Meisenbach, 1995) was shown in Fig. 2.5 below:

Figure 2.5: Derby rib technique Strutt built a second row of vertically arranged needles, between the horizontal ones of the knitting-frame. They take over the sinker loops and transform them into needle loops. Contrary to the normal purl stitches, the attachment could be shifted in and out so that one could make rib or plain fabrics as required, (Meisenbach, 1995). Therefore fabrics, produced by Lee frame were known as plain knits.

2.4 Powered knitting machine:

In 1769, the manual frame was successfully adapted to rotary drive, Samuel Wise, (Doric Public company, 1972; David, 2001). He replaced the foot pedals with a power-driven rotary shaft whose tappets caught against arms and levers to move the working parts to increase productivity.

- 24 - In 1798 Frenchman Monsieur Decroix arranged the needles radially into a corona which rotates and thus moves the needles one after the other through the knitting stages creating seamless tubular fabrics, as seen in Fig 2.6, (David, 2001; Thomson, 2005; Meisenbach, 1995). The frame was successfully adapted to a rotary drive, thus the circular knitting frame was born (David, 2001; Meisenbach, 1995).

Figure 2.6: View of radial arrangements of knitting needles

In 1805 the jacquard control apparatus, introduced by Joseph Marie Jacquard for weaving looms, was applied successfully to the knitting machine to form the same decorative purpose: Individual movements of knitting transfer needles, sinkers or guide needles were used for patterning, (Meisenbach, 1995). By 1812 there were over 25000 frames assumed to be in use, most of them in the three mentioned towns, namely: Derby, Nottingham and Leicester, (Cooper, 1991). The production improved to 1000 to 1500 loops per minute, (David, 2001; Knitting Together, 2002). In 1847, Matthew Townsend obtained a patent for his invention of the latch needle by which the formation of stitch became easier. The result was simplification of the mechanism, increase in production speeds and reduction of costs, (Doric Public company, 1972; David, 200; Meisenbach, 1995). Between 1850 and 1860 the circular knitting machine, has been developed from the English circular knitting frame, (Thomson, 2005; Meisenbach, 1995). It was initially equipped with stationary bearded needles in vertical position, later on; it was built with latched needles, which can be individually moved. This is characteristic of a circular knitting machine. These machines, produced small diameter tubular fabrics, at a later stage

- 25 - larger diameter was built to produce wider fabrics, (David, 2001; Meisenbach, 1995). Thoughts began to simplify the knitting action and introduce automatic mechanisms to replace hand- controlled operations. Fig 2.7 shows a hand-operated knitting machine.

Figure 2.7: Hand-operated circular knitting frame 2.5 High speed automatic knitting machines:

In 1864, William Cotton of Loughbororugh transferred the hand controlled power driven rotary frame into a high-speed automatic multi head straight bar frame. This speeded the transition of knitting from a cottage based to a mass production industry, (Doric Public company, 1972; David, 2001; Meisenbach, 1995). In 1878 D, Griswold got a patent for a circular knitting machine, which could produce plain or ribbed tubular fabrics in any desired distribution. The vertical cylinder needles are enhanced by horizontal dial needles and individually movable in radial slots. This led for the first time to two new denotions: small rib machine and large rib machine, (Meisenbach, 1995). In 1910, the firm Robert Walter Scott in Philadelphia was granted for interlock fabrics composed of two crossed double knit fabrics, (Meisenbach, 1995). In 1939, Mayer and Cie introduced mass line production of circular knitting machines. Fig 2.8 shows the first machine introduced by Mayer and Cie, (Meisenbach, 1995; Mayer & Cie, 1999).

- 26 -

Figure 2.8: First Mayer and Cie circular Knitting machine

The machines have developed with mechanically controlled and operated movements with exact requirements of modern knitting technology. The mechanical pattern and programming data for controlling the machine is stored in the form of punched cards, chains, rack-wheels, peg drums, and element butt arrangements. Hover emphasize the limitations of mechanical movements, which are expensive to manufacture, slow and cumbersome in operation, difficult to adjust or alter and subject to friction and wear, etc., (David, 2001). These limitations lead to look for alternative systems to facilitate them. The electronics, hydraulics, and fluidics provide alternative systems for these difficulties, (David, 2001).

2.6 Electronic knitting machines: In 1963, the electronic advancement began at the international textile machinery exhibition ITMA in Hanover. The first electronic needle selection is demonstrated by the firm Morat on its film taper-controlled (Mora tonic), which later on gets into serial production 1964, see Figure 2.9 (David, 2001; Meisenbach, 1995). Electronics offer the decisive advantages of convenient power-supply, compatibility with existing mechanical components. Electronic do not require being of a size proportionate to their task. Electronic selection is compatible with

- 27 - higher running speeds and eliminates complex mechanical arrangements, thus reducing supervisory requirements. It provides greater versatility as regards design parameters simplifies the modification of repeat sequences and size, style and pattern changing, operations, and in some cases, enables changes to occur whilst the machine is knitting, (David, 2001).

Figure 2.9: Electronic sampling knitting machine

2.7 Advances in knitting technology: The 1970s show the introduction of early computer-aided design (CAD) and computer-aided manufacturing (CAM) systems. Designers used the CAD system to create product designs and transferred them to CAM machines to manufacture the final product. CAD/CAM technology replaced the mechanical shaping and patterning devices on machines with electronic controls. The systems enabled companies to respond quickly to changes in demand, (Knitting Together, 2002) In 1999, Mayer & Cie exhibits as market leader at the ITIMA in Paris, presenting a whole range of new developments. New features include the first electronic machine with electronic individual needle selection in the dial and cylinder cam, and automatic dial cam setting using robot technology, (Mayer & Cie, 1999).

- 28 - In ITMA 2003 Mayer & Cie displayed a cylinder and dial machine with quick-change features requiring one person, one shift to change cylinder and dial, according to required gauges. The gauge is changed by exchanging the cylinder and dial, see Fig. 1.10; it will lend circular knitting machine greater flexibility and productivity, see Figure 2.10, (Mayer & Cie, 2003).

Figure 2.10: Exchangeable cylinder-dial from Mayer & Cie

2.8 Factors determining economy and productivity of a knitting factory: There are many important contributory factors, which determine the economy or productivity of a circular knitting factory. Nevertheless, these factors take on a completely different emphasis depending on geographical region. The problem of staffing in the highly industrialized countries is focused largely on labor’s costs, while in the threshold countries the problem revolves predominantly around the qualification of operating staff. In the former case, minimal resetting times are a priority issue, in the latter; the emphasis is on operating simplicity and the prevention of faults, (Mayer & Cie, 2007).

2.9 Knitting mechanism: Originally, the term (machine) is used to refer to a mechanism on bearded needle frame such as the fashioning mechanism on straight bar frame, (David, 2001). Today, it refers to the complete assembly of the machine, (David, 2001). A knitting machine is thus a device for applying mechanical movement, to either hand or power deriven, to primary knitting elements, in order to convert yarn into knitted loop structure, (David, 2001)

- 29 - 2.9.1 Types of knitting machines:

There are two main groups of knitting machines with regard to yarn presentation and yarn processing, (David, 2001; Meisenbach, 1995). A yarn presented horizontally and converted in to a row of loops is commonly referred to as weft kitting machine). In weft knitting machines, needles move individually or collectively to perform knitting process. In the other type the yarns are aligned longitudinally (known as machine). The following Fig. 2.11 shows the summary.

Knitting machines

Weft knitting machines Warp knitting machine Collective needle motion Individual needle motion Collective needle motion

V-Bed machines Straight bar machie

Circular knitting machine Loop wheel Machie

Figure 2.11: Knitting machines organization chart 2.9.2 Local knitting Industry:

The majority of local knitting industry is based on weft knitting and only recently that warp knitting technology is been introduced.

2.9.3 weft-knitting machine general features Following are the general features of circular knitting machine (David, 2001; Meisenbach, 1995): 1. The frame, which is normally free standing and either circular or rectangular according to the needle bed shape, provides the support for the majority of the machine mechanisms. 2. Drive system co-ordinates the power for the drive of devices and mechanisms.

- 30 - 3. The yarn supply consists of the yarn package, tensioning devices, yarn feed control and yarn feed carriers or guides. 4. The knitting system includes the knitting elements, their housing, drive and control as well as associated pattern selection and garment length control device (if equipped). 5. The fabric take away mechanism includes fabric tensioning, wind up, and accommodation devices. 6. Cam-set up. 7. The quality control system includes stop motions, fault detectors, automatic oiling systems…etc.

2.9.3.1 Knitting elements: Knitting elements includes parts involved directly in stitch formation (Meisenbach, 1995): 1. The needle 2. The holding down – knock over 3. The sinker link 4. The needle carriers (needle cylinder, needle dial). 5. Cams

2.9.3.1.1 Needles: The hooked metal needle is the principal knitting element of the knitting machine (David, 2001). The needles are used to form stitches. Thus, the primary function of them is for interlooping yarns. They perform different functions depending on the knitting technique and the needle type (David, 2001). They link the new yarn loops with knitted loops and carry the knitted loops during stitch formation cycle. During the early stages of knitting cycle, the hook of a needle is opened to release the retained knitted loop to slide over the closed hook, (Manchester M.Sc. Lectures, 2007). All needles must therefore have some method of closing and opening the needle hook in order to retain the new yarn loop and exclude the knitted loop. Depending on how the closing of the hook is achieved, (bridge formation) knitting needles are subdivided into the following three groups (Manchester M.Sc. Lectures, 2007): 1. The bridge formation is achieved by applying an external force.

- 31 - 2. The bridge formation is carried out due to the relative movement of knitted loop and the . 3. The bridge formation is accomplished with an additional closing element.

2.9.3.1.1.1 Bearded needle:

Figure 2.12: Bearded needle

This needle is used in first knitting machine of William lee in 1589 as shown in Fig. 2.12; it is made from steel wire or from punched steel plate. It consists of the following parts, (Manchester Msc Lectures, 2007): 1. The head, where the stem is turned into a hook to draw the new loop through the old loop. 2. The beard, which is curved down wards continuation of the hook that is used to separate the trapped new loop inside from the old loop as it slides off the needle eye beard. 3. The eye, or groove, cut in the stem to receive the pointed tip of the beard when it is pressed thus enclosing the new loop. 4. The stem around which the needle loop is formed 5. The shank or butt, which may be bent for individual location is the machine or cast with others in a metal (lead). This type of needles has the disadvantage of requiring an external pressing edge to close the bearded hook and enclose the new loop. This is achieved by mounting all needles on to a needle bar. The beard is then closed by either moving a second metal bar, called the presser bar, towards the needle beards or rotating the needle bar towards the stationary presser bar, (Manchester M.Sc. Lectures, 2007).

- 32 - 2.9.31.1.2 Latch needle: Mathew Townsend introduced this type of needle in 1847 (David, 2001 and Manchester M.Sc. Lectures, 2007). The latch is more expensive to manufacture than the bearded needle and is more prone to making needle marks in knitting, but has the advantage of being self-acting or loop controlled. Hence, the problem of pressing edge on the bearded needle has been solved, the result was simplification of the mechanism, increase in production speeds and reduction of costs (Meisenbach, 1995). For this reason, it is the most widely used knitting needle in weft knitting and is sometimes termed the automatic needle. Precisely manufactured latch needles are today knitting very high quality fabrics at very high speeds, (Microsoft Corporation, 2000). It consists of the following parts; shown in Figure 2.13, (David, 2001):

Figure 2.13: Latch needle and its parts where: 1. Head hook 2. Latch 3. Noucat (latch spoon) 4. Rivet 5. Latch-blade 6. Latch spoon 7. The stem 8. The butt 9. The tail

2.9.3.1.1.3 Compound needle:

Figure 2.14: Compound needle and its parts

- 33 - This type of needle, refers to Fig. 214 is introduced in 1856 by Jeacock of Leicester patent. It consists of two separately controlled parts the open hook and the sliding closing elements, mostly used on warp knitting machines, (David, 2001; Meisenbach, 1995). the compound needle has a short, smooth and simple action, without latch or beard inertia problems. The slim construction and short hook makes it suitable for the production of plane, fine warp knitted structures at high speeds, (Manchester M.Sc. Lectures, 2007).

2.9.3.1.2 The holding down – knock over: The main feature of fabric holding-down mechanism in the circular knitting machine is to stop the fabric from being lifted during the knitting process, (Mayer & Cie, 2007). The knock over is the stage at which the needle passes through old loop by drawing a new loop.

2.9.3.1.3 Sinkers: The sinker is a thin metal plate of different shapes, to perform different functions according to the machine knitting action and movement. The sinker is positioned at right angles from the hook side of the needle bed, between adjacent needles as shown in Fig. 2.15 (David, 2001).

Sinker Needles

Figure 2.15: A sinker between two adjacent needles

The functions of the sinkers depend upon their shape: loop formation, holding down and knocking over, Fig. 2.16 shows different types of sinkers, (Meisenbach, 1995).

- 34 -

Figure 2.16: Different sinker constructions

2.9.3.1.4 The needle carriers (needle cylinder, needle dial): A grooved vertical cylinder is a main part in knitting machine above which is a round grooved disc known as dial. The needles are attached to these grooves and moving freely to knit the fabric, which passes, through the space between the cylinder and dial.

2.9.3.1.5 Cams: Cams are the devices, which convert the rotary machine drive into a suitable reciprocating action for the needles and other elements, (David, 2001). The cams are carefully profiled to produce precisely timed movement and dwell periods and of two types engineering cams and knitting cams, (David, 2001).

2.8.3.1.5.1 Engineering cams: The circular engineering cams or high-speed eccentrics control the motion of bars of elements, which move en masse as single units in cottons patent and warp knitting machines. They are attached to a rotary drive shaft situated parallel to, and below, the needle bar. A number of identical cams are positioned along the shaft to ensure correctly aligned movement. The drive is transmitted and adapted, via cam-followers, levers, pivots and rocker shafts. One complete 360 degree of revolution of the drive shaft is equivalent to one knitting cycle, and it produces all the required movements of the elements in their correctly timed relationship. The eccentric is a form of crank, which provides a simple harmonic movement with smooth acceleration and deceleration. It is the result of adapting the simple motion and

- 35 - modifying it to the requirements of the warp-knitting machine. So that even dwell (stationary periods) in the element cycle can be achieved, (David, 2001).

2.9.3.1.5.2 Knitting cams: The angular knitting cams, act directly onto the butts of needles or other elements to produce individual or serial movement in the tricks of a latch needle weft-knitting machine. The knitting cams are attached, either individually or in unit form to a cam-plate, and depending upon machine design. They are fixed, exchangeable or adjustable, (David, 2001).At each yarn feed position there is a set of cams consisting of at least a raising cam, a stitch cam and an upthrogh cam, whose combine effect is to cause the needle to carry out a knitting cycle. These cams can be represented by three triangles, (Manchester M.Sc. Lectures, 2007) as shown in Fig. 2.17

Fig 2.17: Knitting cams triangle 1. Raising cam: The central triangle represents the raising cam, its function to raise the knitting needles, causes the function such as tuck, clearing, loop transfer or needle transfer height, depending upon machine design, (David, 2001). 2. Stitch cam: It controls the depth to which the needle descends, thus controlling the amount of yarn drawn into needle loop; it also functions simultaneously as a knock –over cam, (David, 2001). 3. Guiding cam: The function of the Guiding cam is to lower the raised knitting needles and to prevent the raising needles from overshooting, (Manchester M.Sc. Lectures, 2007).

- 36 - Generally, knitting cams fixed on to a cam plate they realized the movement of the knitting needles between two dead centers causing the yarns into loops and engineering fabric production, (Manchester M.Sc. Lectures, 2007).

2.9.3.2 Knitting cycle: The correct sequence of the knitting steps is known as the knitting cycles. It consists of the following steps: 1. The yarn has to be provided to the knitting zone (known as yarn laying). 2. Convert the yarns into loops (loop formation). 3. Closing the needle hooks (bridge formation). 4. Linking up, in which the newly formed yarn loops are drawn through the knitted loop in the needles, converting the yarn loops into knitted loops and knitted loops into new stitches. However, the order in which these are carried out will depend on the knitting technique and the knitting needle.

2.9.3.2.1 Knitting cycle of latch needle: 1. Holding down: The needle begins with its forward movement from its backward dead centre i.e. from its back ward rest position. During this movement, the knitted loop in the needle hook is also forced to move forward due to the interaction of the fabric takedown tension and the needle movement. This forward movement of the knitted loop is extremely important because this clears the way for the needle to move forward without any obstruction. 2. Latch opening: Due to the fabric, takedown force the knitted loop would remain on the knocking over edge of the needle bed. As a result when the needle continues to move forward the knitted loop would be forced to slide back in the needle hook. Due to these relative movements of the needle and the knitted loop in opposite directions, at a predetermined time the knitted loop would strike the latch and force it to open. The latch opening time would be determined by the geometry of needle and knocking over jack, it would also depend on the yarn diameter i.e. yarn count.

- 37 - 3. Clearing: The forward moving needle would cause the knitted loop to clear the opened latch. The knitted loop would be held on the needle stem until later. Soon after clearing, the forward movement of the needle is completed. The needle movement during steps 1 to 3 is referred to as the forward stroke of the needle and it is defined by the geometry of the needle and the raising cam. 4. Yarn delivery: The needle begins to move back. During the early stages of this movement, a new yarn is laid across the hook of the needle. Due to the backward movement of the needle, the knitted loop is pressed against the knocking-over edge of the needle bed. 5. Latch closing: The needle continues with its backward movement. Due to this movement, the knitted loop, which is held on the stem, is forced to move forward towards the needle hook. This results in the knitted loop initially being moved underneath the latch, and then it forces the latch to rotate and close the hook area. The new yarn is trapped in the hook of the needle. 6. Landing: The needle continues with its backward movement, and this forces the knitted loop to move on to the closed latch and then to continue moving towards the needle hook on the latch. 7. Casting off: Due to the backward movement of the needle the knitted loop is thrown off (castled off) the hook. From this point onwards, the needle hook begins to pull the new yarn through the knitted loop. As a result, the knitted loop is converted to a stitch and the new yarn pulled by the needle hook becomes the new knitted loop. 8. Knocking over: The needle reaches the backward dead centre and a new knitted loop is formed in the needle hook. In other textbooks, the knitting cycle of latch shorted on five steps only (shown in Figure 2.18):

- 38 - 1. Rest position

2. Latch opening 3. Clearing height 4. Yarn feeding 5. Knocking over and loop length formation

Figure 2.18: Knitting cycle of latch needle

2.10 Basic knitted fabrics:

There are four basic knitted fabrics, which are illustrated in the fowling Figures 2.19, 2.20, 2.21 and 2.22 respectively.

1. Plain fabrics:

Figure 2.19: Plain kitted fabric

- 39 - 2. Rib fabrics:

Figure 2.20: Rib knitted fabric 3. Purl fabrics:

Figure 2.21: Purl fabric

4. Interlock fabrics

Figure 2.22: Interlock knitted fabric

2.11 Optimizing knitting performance and fabric quality:

The term quality is sometimes used, when referring to wales and courses per inch or centimeter, either in knitted or finished relaxed state, (David, 2001). The wales and courses constitute the knitted fabric structure when they are meshed together at right angles. The basic need in quality is to engineer the product; it means that specifications are prepared which set up

- 40 - standards and dimensions that can easily be checked on the factory floor, (Harry, 1964). Genarly textile testing is application of engineering knowledge and science to the measurement of the properties and characteristics of, and conditions affecting, textile fibers, yarns and material, (Ellot et al, 1960). Testing is primarily concerned with the evaluation of quality of product resulting from changes in machine performance, and quality control techniques, (Ellot et al, 1960). In other situations, the quality of weft knitted fabric is related to knitting parameters, including the number and area of knitting faults which are produced by knitting process and faults originated from yarn faults, ( Dariush; Mohammad, 2007). In addition, the fabric quality is used to describe the nature of the fabric density (cover factor), (Australian wool innovation, 2007). It is assumed that poor quality of yarn appearance causes poor quality of fabric, but the effect of yarn count, raw material and fabric structure is important too, (Dariush; Mohammad, 2007) .The appearance of knitted fabric can be strongly affected by the yarn used beside other factors such as wrong setting of the machine, (Meisenbach, 1995). Therefore, the quality is affected by yarn, fabric structure and machine. According to the above information, several studies had been done to improve the quality of knitted fabric and knitting performance, within the component of knitting machine elements, fibers to yarn or fabric structure. The knitting machine and their operating elements have always moved forward with the latest available manufacturing technology in the field of precision on mechanics. Porcelain was applied at the contact points between yarn and knitting machine elements to reduce friction, minimize tension and improve yarn passage, (Oerdyck et al, 1972). At the beginning of the eighties, German circular knitting machine manufacturer Mayer & Cie, reduced the yarn deflection points, at knitting zone in the circular knitting machine to four instead of eight, (Mayer and Cie, 1980). This halved reduction in the deflection points has minimized the stress and friction on the yarn. The development represented a major step forward for the circular knitting industry in terms of quality of knitted fabric and productivity. Knitting tension is an important quantity having a bearing on the stitch length of the knitted fabric and therefore, on its quality and properties, (Dias et al, 2002).

- 41 - Several devices were added to the circular knitting machine to improve the process quality. One example, the sensors which are capable for stopping the knitting machines when the yarn in-put tension falls below required limits (Shankam, 2005). Other sensors are capable of detecting machine elements such as broken needles, closed latches and broken sinkers and of stopping the knitting machine immediately, (Mário et al, 1999). Earlier researches showed that the length of a yarn knitted into a single loop will determine such overall fabric qualities such as hand, comfort, weight, extensibility, finished size, cover factor and most important fabric dimensional stability. Therefore, the single knitted loop must be of the correct size and shape for a given set of fabric performance, (Mehmad et al, 2002). Ucar, N, Realff, ml, et al added a device called quality adjusting pulley (Q A P ) to the knitting machine to be driven by the main drive of the machine and drives the yarn delivery wheels of positive storage to maintain constant yarn delivery rate as well as prevention of variation in stitch length, (Ucar et al, 2002). Some studies were carried out by altering machine settings to measure fabric properties. A study carried out to gain a better understanding of the bending and shear behavior of knitted fabric. In this study, several plain knitted fabrics with different tightness factors were produced in the laboratory. The results indicated that the increase in the tightness factor and relaxation of fabric generally lead to increase in fabric rigidity against bending and shear deformation (mechanical properties), (Mehmad, 2002). Based on the distribution of fibers, this will influence the yarn and metal friction during knitting which in turn will affect the limited tension and consequently the machine efficiency and fabric characteristics. Based on this fact many studies were carried out to generate such fabric properties. National textile center had studied the effect of very fine denier of polyester fiber in the blend with cotton fibers of equal fineness on knitted fabric characteristics: dimensional stability and mechanical properties. The fabric subjected to the test of influence of load and deformation to establish its geometrical and mechanical characterization, (Rose, 1993). Computer software was developed to help the knitting manufacturers to be able to predict and improve the consistency and reliability of the knitted products while increasing the efficiency of knitting operation by reducing time and receiving better fabric performance, (Thomson, 2005).

- 42 - Some studies were carried out to measure the properties of knitted fabric made from yarns produced by different spinning systems. A study carried out by (Babar, 2005) concluded that under two different yarn spinning systems (ring and air-jet) fabric strength, of ring spun yarn knitted fabric is greater as compared to air-jet spun yarn. The results indicated that yarn and fabric strength as well as fabric weight showed significant effects on machines and blending ratio, (Babar, 2005). Modern studies were carried out to improve the quality of fabric evaluation; an automatic fabric evaluation system is developed to analyze knit structures and objectively evaluate fabric properties, by Abu-Ana et al. In this system fabric images are captured with a CCD camera and digital images are processed by histogram equalization, binary, morphological, operators and pattern recognition, (Abou-Ana et al, 2003). A computer- based method, to determine knitted fabrics' density was proposed based on measuring single loop parameters. The system has the advantage of the proposed approach of its possibility to be applied in real time to supervise knitted structures at various stages of the production cycle, (Bożena, 2006). A new method for classification of knitted fabric by using image analysis and neural network is introduced by Ebraheem Shady et al. This new method is more accurate than the traditional subjective human inspectors, (Ebraheem and et al, 2006). Some modern studies improve knitting quality by design of software to predict fabric properties. (Gravas and kiekens, et al, 2006), designed a software according to the existing literature available. the program can be used to determine the weight of knitted fabrics in different relaxing conditions by entering process and material variables such as the type of fabric and fiber, knitting machine gauge, yarn count fabric loop length and tightness factor. The determination of fabric weight is dependent upon the dimensional parameters of kc, kw, ks and R, constants which have been entered into the system. The system can be used for single and double knitted structures (Gravas, and Kiekens, 2006).

- 43 - Chapter Three:

Materials, methods and equipment

- 44 - 3.1 Materials:

In this research work, yarns made from different counts and fibers, were used, namely barakat and acala cottons. The yarns were procured from various local spinning and knitting mills: Khartoum North Fine spinning Mill, Turkish dying mill and other local mills. The following Table 3.1 shows the yarns delivered to the Hashmab Knitting Factory where the yarns were processed in this experimental work in order to produce samples of knitted fabrics. All yarns were subjected to quality tests, namely: Actual count, Ne, lea strength and elongation, twist and appearance. The tests of yarns were done in Textile Engineering Quality Control Laboratory – Department of Textile Engineering at Sudan University for Science & technology. All tests were carried out at standard atmosphere: temperature of 20°C ± 5 and relative humidity equals 60 % ± 5. Table 3.1: Yarn quality Material type Waxed cottons Un waxed cotton Property barakat acala barakat acala Ne Nominal 36 .00 30 .00 24 .00 20 .00 24 .00 20 .00 20 .00 20 .00 Actual 36.30 29.90 24.60 20.80 23.70 21.10 19.90 20.80 Twist per cm 10.46 9.29 8.23 8.30 8.53 7.79 7.60 7.56 Strength in kg 33.70 39.70 46.60 62.20 37.70 40.50 61.40 42.10 Lea Elongation cm 4.70 3.40 4.20 4.30 4.00 4.60 4.500 3.90 strength Elongation % 6.10 4.79 6.30 5.80 6.10 6.70 6.40 5.90 Appearance grade D B B B B B B B

From the above table the following can be deduced: 1. No significant differences can be observed between the original and the actual counts 2. Measured twist values were found to be on the high side for knitting, for example twist per cm, tpc, were 10.4 compared with say 3.9√36 ÷ 2.45 = 9.2 tpc. Also for Ne 24, the measured count of 8.23 compares with say 4√24 ÷ 2.45 = 7.7 tpc. 3. However, although the twist values are rather high for knitting, yet no problems were encountered during the knitting processing of these yarns.

- 45 - 3.2 Methods: 3.2.1 Introduction:

A survey of the local knitting factories had been done and observations of the knitting performance were made with object of estimating the variables affecting the knitting operations. Fabric samples, in the framework of this research, were produced, by using a double jersey-knitting machine, with application of different variables. Fabric testing will be made and matched with machine performance, to set mathematical and physical formulae for optimum fabric quality. The formulae could be used to engineer the fabric production. Such variables, which, affect knitting performance and the quality of knitted fabrics include the following:

1- Machine settings: Most important are:  Tension adjustment  Loop length  Machine speed  Air conditions

2- Yarn characteristics:  Count  Materials  Twist  strength The experimental works for this study were carried out in Elhashmab Knitting Factory, located at Omdurman. The machine, used for the production of the knitted fabric samples, is a double knitting machine described in section 3.4.The machine stands on a level ground, being checked with a water-level, two water coolers (adiabatic cooling), each 4000ft, supplied an air of 27°c and a relative humidity of about 50%. Following are the details of the survey, the procedure of the investigation of knitting parameters and statistical package.

- 46 - 3.2.2 Survey of the local knitting industry: The survey contained different aspects as follows: 3.2.2.1 Primary data: Such as name of the factory and date of establishment: 3.2.2.2 Layout and machinery arrangement:

The provided space for the worker to move in the knitting room is recommended economically to be within the limits of 1.2 to 1.5 meters, (Randolph, 1951). The minimum value of 1.2 meters is perhaps to maintain human effort (skill) to do the work efficiently. (Examples: threading the yarn, operating the machine, removing the fabric …etc.). However, the maximum value of 1.5 meters is to maintain the time as well as material quality. This space was measured during this survey in order to investigate the proper arrangement of the machines so that the workers do their job perfectly

3.2.2.3 Activities: Such as knitting, Weaving and /or garment manufacture.

3.2.2.4 Technology and types of installed machinery: The type of technology whether weft or warp knitting technologies.

3.2.2.5 Type of yarns used: Yarn count

3.2.2.6 Type of products and production efficiency: Single jersey, double fabric and others.

3.2.2.7 Operating conditions and cleaning efficiency:

It is well stated in textbooks that textile manufacture should maintain relative humidity within specific limits about 60% to 50%. Although experience showed that, these limits can be achieved in the small factory rooms by using of evaporative coolers. A relative humidity above 60% was achieved in small knitting room at Industrial Research and Consultancy Center by using two evaporative coolers.

- 47 - 3.2.3 Investigation of the knitting parameters: 3.2.3.1 Investigation of effect of initial machine setting on knitting performance: 3.2.3.1.1 Production of knitted rib fabrics by initial & adjusted settings:

It has been planned to produce the first knitted rib fabric samples on the machine using the initial setting of tension and loop length. The initial machine setting is referred to the manual setting which done by the knitter in the local knitting factory. It has been observed weakness in the manual setting of tension during the survey. In the initial machine settings, the stitch length and tension levels were measured and recorded. The tension was measured by yarn tension meter. The stitch lengths were taken directly from the knitting machine scale. It was found that the initial setting of the machine was based on different tension levels in the feeders and accordingly this gave different loop lengths. Fabric samples were produced, at these settings, for later references and comparisons. After checking the machine setting, it was adjusted to a new setting level. The new setting applied in this work, was based on equal loop lengths and equal tension levels in all feeders of the knitting machine. Tension of feeders was adjusted to a value of 5cN, as stated in textbooks as acceptable level for knitting tension, (David, 2001). An adjusted loop length of 5 mm was applied; it was approximately equal to average loop lengths of initial machine setting which was 6 mm. A second fabric sample was produced at this new setting. The two fabrics were produced from, acala and barakat cotton yarns (Ne 24/1). The fabric samples were subjected to quality tests. The tests were carried out in Textile Engineering Quality Control Laboratory – Department of Textile Engineering at Sudan University for Science & technology. The samples produced by the two setting levels were subjected to comparison test.

3.2.3.1.2 Fabric quality tests: The applied quality tests were fabric structure, fabric width in cm, shrinkage, weight per square meter, fabric extensibility and pilling. The tests carried according to the British Standards (Bs).

- 48 - i. Fabric structure: The fabric, after being doffed from the knitting machine was left in the knitting room at the standard air conditions for 48 hrs to reach the equilibrium state, i.e. dry relaxed state. Courses and wales per cm were measured using counting magnifying glass in accordance to Bs 2862. Courses per cm were measured at different areas of the fabric, 12 readings at different serial meters. Results were tabulated in tables. The same procedure has been done to measure wales per cm. The measurements were carried out at Hashmab Knitting Factory. ii. Fabric width and shrinkage measurement at the dry relaxed state: The fabric after being doffed from the knitting machine was left in the room at standard conditions for 48 hrs to reach the equilibrium state, i.e. dry relaxed state. The fabric width was measured using a meter tape Bs 1830. Averages of twelve readings were made. The fabric shrinkage was calculated from the machine circumference i.e machine circumference minus width of relaxed fabric‘. iii. Weight per square meter test: This test was carried out according to the method stated on the Bs. 2471, using a cutter and weighing balance. Twelve readings were obtained for each sample. iv. Fabric extensibility: The test was carried out at Sudan University for Science & Technology in the textile engineering quality control laboratory. The fabric samples were tested for stretch and recovery by using a Fryma fabric extensiometer described in section 2.3.2. The test was done following procedure stated on the Fryma manual in accordance to Bs 4294-1968. v. Pilling test:

An ICI Pilling tester was used. The tester consists of a rotating box lined with cork containing special rubber Tubes around which the samples were wrapped. The samples were put inside the box. The tests were carried out according to the Japanese Industrial Standard (JIS). Two pieces, each 10 cm x 12 cm, were prepared from the specimen in wales and course directions of the fabric. The test specimen is in the natural state, no, tension was applied. The specimen was sewn round the rubber tube using cotton thread; both ends were pasted to the

- 49 - tube by an adhesive tape. The samples were subjected to a rotational speed of 60 rpm for 5 hrs. The pilling picture on the samples were then photographed and compared with standards

3.2.3.2 Investigation of effect of varying loop length: The loop length was adjusted with the adjustable stitch cam through a measuring scale device, which is capable for selecting different stitch lengths as shown in Fig 3.1.

Figure 3.1: Side view of stitch length measuring device

The scale is divided into units starting from 4mm giving a very short length, to 36mm very long stitches. The machine was adjusted to three different stitch lengths, a short length of 5mm, a medium of 16mm and a long 28mm; in order to investigate the effect of the loop length on the knitting performance. Figure 3.2 shows top view single feeder stitch length measuring device.

Figure 3.2: Top view of stitch length measuring device

The machine running time was kept constant at 10 minute for each fabric setting. Barakat cotton yarn Ne 36/1 was used for running the experiments. The produced fabrics were then subject to quality tests. Correlation test should be applied in order to derive mathematical

- 50 - formulae. The value of coefficient of correlation varies between 0.0 and 1.0; the relation becomes stronger as the value approaches to 1.0. Positive value indicates positive relationship while negative value indicates inverse relationships.

3.2.3. 2.1 Production of fabric samples by varying loop length: i. Production of fabric sample at loop length of 5 mm: All stitch cams were adjusted to the (5 mm) loop length on the knitting machine scale. The machine was operated for ½hr and then stopped, the fabric was doffed and left for 48hrs in the standard air condition of about 27˚c and 55% RH. The fabric structure tests were applied, and results were recorded. ii. Production of fabric sample at loop length of 16 mm: All stitch cams were adjusted to the (16 mm) loop length on the machine scale. The machine was operated for ½ hr and then stopped. the fabric was doffed and left for 48hrs in standard air condition of about 27c° and 55% RH. The fabric structure tests were applied, and results were recorded. iii. Production of fabric sample at loop length of 28 mm: All stitch cams were adjusted to the (28mm) loop length on the scale. The machine was operated for 1/2hr and then stopped, the fabric was doffed and left for 48 hrs in the standard air condition of about 27 c° and 55% RH were shown. The fabric structure tests were applied, and results were recorded.

3.2.3.2.2 Fabric quality tests: The fabric samples produced by the adjusted three different stitch lengths were subjected to quality tests: fabric structure, width, weight and extensibility. The results were matched with loop length to derive relations between loop lengths and fabric properties in order to formulate mathematical formulae.

3.2.3.3 Investigation of effect of yarn count (Ne): Barakat yarns of different counts Ne 36, 24 and 30 were used for this experiment and processed into knit fabrics. The fabric samples were subjected to quality control tests.

- 51 - Correlation test were be applied in order to derive mathematical and physical formulae similar to the tests of samples of different loop length.

3.2.3.3.1 Production of fabric samples by varying yarn counts: At equal machine setting level and same operating conditions, fabric samples were produced from the above-mentioned yarn counts Ne (36, 24 and 30).

3.2.3.3.2 Fabric quality tests: The fabric samples produced by three different yarn counts were subjected to quality tests similar to these of fabrics produced by varying loop lengths.

3.2.3.4 Investigating of yarn waxing on knitting performance: Waxed and un-waxed barakat cotton yarns Ne 20, shown in Table 3.1 were used for the experiment. The purpose of this experiment was studying the effect of friction between yarns and knitting machine elements, since waxing influences yarn surface.Tthe tension build-up during operation was measured for both waxed & un-waxed yarn.

3.2.3.4.1 Measurement of tension build-up at different zones: The tension was measured at different zones in the machine namely package zone, before feeding zone and at knitting zone, explained in Fig.3.3. After operating the knitting machine for 10 minutes the tension levels were read using yarn tension meter, described in section 3.4.2. A comparison was made to the results obtained.

Figure 3.3: Zones where tension was determined for the effect yarn waxing

- 52 - 3.2.3.4.1 Production of fabric samples by using waxed and un-waxed yarns:

At equal operation condition, fabric samples were produced by using waxed and un- waxed yarns. 3.2.3.4.2 Fabric quality tests: The fabric samples, made from waxed and un-waxed yarns, were subjected to abrasion test to determine the abraded loss weight. Frank abrasion resistance tester, described in section 2.3, was used. The tests carried out following the procedure stated in the Frank operation manual.

3.2.3.5 Investigating of machine speed on knitting performance: The Terrot circular knitting machine is provided with variable speeds which can be adjusted by an attached controlling device. For this experiment Barakat cotton yarn Ne 24 was used. The yarns processed into knitted fabric by adjusting the terrot knitting machine to 5 different operating speeds. The speeds are approximately equal to 25 (very low), 32 (low), 35 (medium) and 40 (high ) respectively. Tension levels and loop lengths were adjusted to value of 5cN for all feeders. It has been assumed that tension levels may be affected by increasing knitting machine operation speed.

3.2.3.5.1 Measurement of tension (cN) build-up at knitting zone For each operating speed, the level of tension was determined at knitting zone using the mobile yarn tension meter mentioned earlier. The rate of breakage was measured for each operating speed. The machine was operated for half an hour for each operating speed.

3.2.3.5.2 Rate of breakage: The rate of breakage was measured for each operating speed. The results were subjected to statistical correlation test.

- 53 - 3.3 Statistical analysis: Statistical package for social science (Spss) computer program was used for this analysis, (Ray for Publishing and science, 2008). The program is suitable for both statistical measures and creation of different graphs. The results of determined fabric quality tests obtained by initial and adjusted machine settings were subjected to statistical pair difference test. The program computes the difference between the values obtained by initial & adjusted settings of loop length & tension level which determine the fabric properties. Normally both values should be equal and the adjusted values are the base of comparison. In addition, the program tests whether the difference is significant between the values obtained by the two setting levels or not, beside the confidence intervals. The values of determined fabric quality tests: fabric structure, width, weight and extensimeter, obtained by adjusted loop lengths were subjected to statistical correlation test. A correlation coefficient is a number between ‘-1’ and ‘1’ which measures the degree to which two variables are linearly related. Correlation coefficient of ‘1’ indicates perfect positive linear relationship between the two variables. A Correlation coefficient of ‘– 1’ means that there is perfect inverse linear relationship between the two variables. A correlation coefficient of ‘0’ means that there is no linear relationship between the variables. The program automatically outputs the values of correlation coefficient together with significant level. Double stars ‘**’ in the output means that there is strong relationship while single star ‘*’ indicates week relation. For the level of significant; the statistical significant is indicated with p-values less than 0.05, p stand for probability. Scatter plots illustrate the type of correlation whether positive, negative or no association. It provides the shape: linear, curved, etc. The results were subjected to statistical regression test. The program outputs a table contains formula type with constant ‘A’, regression coefficient ‘B’, and other statistical measures. The generated information uses for establishing mathematical formulae, since the program defines the type of the equation whether linear, a second degree, or a third degree. The results of values of determined fabric quality tests: fabric structure, width, weight and extensimeter, obtained by different yarn counts were subjected to similar statistical correlation test as was done with adjusted loop lengths. The output information uses for

- 54 - establishing mathematical formulae to explain the relation between the yarn counts and knitted fabric properties, using the same procedure. The results of values of determined tension build-up by increasing knitting machine speeds were subjected to correlation test. The program tests whether any of those averages are significantly different from each other. Scatter plot shows the type of the relation between the increasing speed and tension build-up for each speed. The program also outputs the value of the correlation coefficient and its significant value. The results of rate of breakages for the different speeds were subjected to correlation test. Again, the program outputs the correlation coefficient value and the scatter plot shows the type of the relation. The results of determined tension build-up, by rubbing of waxed and un-waxed yarns with machine elements were subjected to statistical pair test. It was assumed that the waxing of the yarns prevents them from direct rubbing with machine elements and by doing so reduces tension build-up during machine operation. The program outputs the differences in tension build-up by using waxed and un-waxed yarns with significant level beside confidence intervals. The results of weights of abraded waxed and un-waxed fabrics samples were subjected to statistical pair test. The two types of fabrics were subjected to the same abrasion cycles; it is then assumed that fabric samples made from un-waxed yarns will abrade more than the samples made from waxed yarns. The program outputs the differences in sample fabrics weights with the significant level.

- 55 - 3.4 Equipment: 3.4.1 Machine used:

A double Terrot Circular knitting machine, with the following particulars was used , as shown in Fig.3.4. 1-Diameter 17inches (43.18cm) 2- Gauge 12 needles per inch 3- Year of manufacture 1960 4- Two types of latch needles: Cylinder needles long, NO. 77 Dial needles short, No.54 5- Variable speed motor (applied speed range 30 to 44rpm) 6- Feeding with roller device and adjustable tension 7- Quality systems provided (stop motions 24 voltage)

Figure 3.4: Terrot double knitting machine (Hashmab Factory)

3.4.2 Measuring Devices: The measuring devices used in this study were as follows: i. Hygrometer: The hygrometer was used to measure the air condition in the knitting room as shown in Fig.3.5.

- 56 -

Figure 3.5: Hygrometer (Industrial Research and Consultancy Center) ii. Yarn tension meter:

A mobile tension meter was used to read the yarn tension during the knitting process, as shown in Figure. 3.6.

- 57 -

Figure 3.6: Yarn tension meter (Weaving and Knitting Laboratory – Department of textile Engineering Technology – Faculty of Textiles - University of Gezira)

- 58 - iii. Fryma Fabric Extensiometer:

The Fryma fabric extensiometer is a tester capable to determine the stretch and recovery of a textile fabric with precision at break. The apparatus can stands on top of a table or desk, Fig 3.7 a. It consists of a loading frame with clamps and a screw-tensioning device, two 3kgm loading weights and sample cutting template. The fabric sample is to be sandwiched between the clamps. The movable wheel has a metallic ring where loads can be hanged as shown in Fig 3.7 b.

Figure 3.7 a: Fryma Fabric Extensometer (Q.C. Laboratory – Department of Textile Engineering – University of Sudan for Science and Technology)

Figure 3.7 b: Fryma Fabric Extensiometer

- 59 - iv. Abrasion resistance tester:

Abrasion resistance tester is a machine for determining the quatity of material worn away by friction. Fig 3.8 shows a Frank abrasion tester which consists of the following parts: 1- A swivel abrasion head with pneumatic clamping device in which the sample is to be clamped. 2- An air compressor with connection cable and tube to provide air to the pneumatic clamping devices. 3- Erecting table with built-in drive motor. 4- Electric switching elements 5- Adjustable counter. 6 - Load plate.

Clamping device Swiveling arm

Load plate Counter

Drive motor

Pipe

Compressed air pump

Figure 3.8: Abrasion resistance tester (Q.C. Laboratory – Department of Textile Engineering – University of Sudan for Science and Technology)

- 60 - v. Other measuring tools:

Other measuring tools such as balances, measuring tapes and magnifying glass were used in fabric tests were shown in Fig. 3.9 and Fig. 3.10.

Figure 3.9: Electronic balance (Q.C. Laboratory – Department of Textile Engineering – University of Sudan for Science and Technology)

Figure 3.10: Fabric magnifying glass (nby.e.tradeee.com)

- 61 - Chapter Four:

Results and Discussion

- 62 -

4.1 Results of the survey of local knitting industry: 4.1.1 Primary data:

From the results of the survey, knitting industry was introduced in the Sudan earlier, in year 1960 but most of them were established between 1990 and 1999. They concentrated on the capital, distributed around industrial zones: at Khartoum, Omdurman and Khartoum North. However, some of the surveyed industries had other activities than knitting manufacture like clothing manufacture and weaving. Table 4.1 shows the visited 24 local knitting factories, their dates of establishment and their locations. From the table only half of the visited factories invested in knitting manufacture alone. All of the visited factories are private sector. Table 4.1: Primary data about local knitting industry Establishment Industry name Location Activity date Osman Khojalli ---- Khartoum Bahry Knitting & Clothing Omderman Knitting 1960 Omderman Knitting Sudanese 1969 Khartoum Knitting & Clothing Elnou 1979 Omderman Knitting & Weaving Hadiat 1989 Omderman Knitting Awaad 1990 Khartoum Knitting & Weaving Elhohod 1989 Khartoum Bahry Knitting & Weaving Eldar Elshabia 1990 Omderman Knitting & Weaving Elbasigat 1992 Khartoum Bahry Knitting & Clothing Elriah 1994 Khartoum Knitting Friendship 1995 Khartoum Bahry Knitting Elmeisra 1997 Omderman Knitting & Weaving Elhashman 1997 Khartoum Bahry Knitting Elhashmab 1998 Omderman Knitting & Clothing shuhed 1998 Khartoum Bahry Knitting Elfardos 1998 Omderman Knitting Salma 1999 Khartoum Bahry Knitting & Clothing Turkish Dyeing 2001 Khartoum Bahry Knitting & Clothing E.Aziz 2004 Khartoum Bahry Knitting Saad 2005 Khartoum Bahry Knitting Mokhtar 2005 Khartoum Bahry Knitting A.Elmolla ---- Khartoum Bahry Knitting Sujood 2003 Omderman Knitting Rusha ---- Omderman Knitting & Weaving

- 63 - Total 24 24 24 Figure 4.1 shows the geographical location of the different factories in Khartoum, Khartoum North and Omdurman. From the figure, about half of the factories were located in Khartoum North and few in Khartoum.

Khartoum

12.5%

Khartoum Bahry Omderman 50.0% 37.5%

Figure 4.1: Geographical locations of local knitting factories

4.1.2 Local knitting factories layout and machinery arrangement:

Table 4.2 shows results of the measured spaces between machines and walls as mentioned earlier reflecting machinery layout and arrangement. Six factories they allowable spaces measured are less than one meter, about 25%. In other words, factories did not maintain proper space; as a result, the work could not be successful. Then 10 measured spaces are within 1.5 meter, 41.7 % and remain 16 factories not subjected to test.

- 64 -

Table 4.2: Measured space between machines and walls in knitting room Measured space in meters No. of factories Percentage (%) >1 meter 6 25 .0 >1.5 meter 10 41.7 ≥1.8 meter none 0.00 Valid Total (subjected to measurement) 16 66.7 Missing System (not subjected to measurement) 8 33.3 Total no. of factories 24 100

The results of the measured spaces were represented graphically as shown in Figure 4.2. From the figure the large area clearly shows the factories where the proper layout had been achieved. The figure also reflects the eight missing factories, which are not tested for measuring their layout 33.3 %. Beside the six factories which are not provided the proper layout 25 %.

not measured

33.3%

<1 meter

25.0%

>1.5 meter

41.7%

Figure 4.2: Allowable space for worker movement in side knitting factory room

4.1.3 Activities: Normally the small factories have more than one purpose in textile sector such as weaving and knitting or knitting and cloth manufacturing. From Table 4.3 about 12 of the visited factories have knitting only, six of them with activities of knitting and clothing manufacture the remaining factories with purpose of knitting and weaving. The activities were

- 65 - illustrated clearly in Figure 4.3, half of the circle reflects the factories work in knitting only, quarter of the circle represents the factories that work in Knitting & Clothing Manufacture and last quarter of the circle reflects the remain works in Knitting & Weaving respectively.

Table 4.3: Type of activities in local knitting sector Type of activity No. of factories Percentage (%) Knitting only 12 50.0 Knitting & Clothing Manufacture 6 25.0 Knitting & Weaving 6 25.0 Total factories 24 100.0

Knitting & Weaving

25.0%

Knitting & Clothing

25.0%

Knitting

50.0%

Figure 4.3: Type of activities in local knitting sector

4.1.4 Technology and types of installed machinery:

4.1.4.1Technology of installed machinery: All surveyed local knitting factories use weft knitting technology, no warp knitting technology was observed, as shown the following Table 4.4: Most of the introduced machines are weft circular knitting machines, a few weft straight bar knitting machine (passap) were observed during the survey. It was illustrated in Fig. 4.4

- 66 - Table 4.4: Type of technologies in local knitting sector Technology type No. of factories Percentage (%) Weft Knitting 23 95.8 Warp Knitting None 0.00 Missing System 1 4.20 Total 24 100

missing

Weft Knitting

Figure 4.4: Type of technologies in local knitting sector

4.1.4.2 Types of machineries installed on local knitting sector:

Both types of circular knitting machines were found double cylinder and single jersey, Table 4.5 shows different types of introduced knitting machines. Some factories invested in double cylinder machines only, some invested in both double and single cylinder machines and no factories specialist on single cylinder machines alone. It was illustrated in Fig. 4.5.

- 67 - Table 4.5: Types of machineries installed on local knitting sector Machines Type No. of factories Percentage (%) Single cylinder only None 0.00 Cylinder and dial 11 45.8 Single and double cylinder 11 45.8 Others 2 8.30 Total no. of industries 24 100

Others

double cylinder

Single & double cyli

Figure 4.5: Types of machinery installed in local knitting industry

4.1.5 Type of yarns used:

The type of yarn counts used in the local knitting factories vary from count Ne 36/1 to Ne 16/1 as shown in Table 4.6. Table 4.6: Type of yarn counts used in local knitting factories

Yarn count (Ne) No. of factories Percentage (%)

36/1 2 8.30 24/1 6 25.0 36/1&24/1 3 12.5

30/1& 24/1 & 36/1 6 25.0 36/1&30//&27/1&24/1&18/1 2 8.30 30/1&16/1 1 4.20 16/1 1 4.20

Total 21 87.5 Missing System 3 12.5 Total 24 100

- 68 - Most factories used medium yarn counts Ne 36/1 & Ne 24/1. A few factories used course yarn counts: Ne 18/1 & Ne 16/1 as shown in Fig. 4.6 most of the visited factories used different yarn counts.

Ne 30/1,16/1 Missing

Ne 36,30,27,24,18,16

Ne36/1

Ne 36/1,30/1,24/1

Ne24/1

Ne36/1,24/1

Figure 4.6: Type of yarn counts (Ne) used in local knitting industries

4.1.6 Type of products and production efficiency:

4.1.6.1 Type of products: Table 4.7 shows the types of products manufactured in local knitting factories. Double fabric and single jersey fabrics are produced in the knitting factory besides other products such as eyelets. Table 4.7: Type of knitted goods produced on local knitting factories

Type of products No. of factories Single jersey 4 Double fabric 9 Others e.g. eyelet 1 Single & Double & Eyelet 6 Total 20 missing System 4 Total 24

- 69 - Fig. 4.7 shows the result clearly: about 37.5% from the visited 24 factories are manufacturing double fabric, 25% produces all types of fabrics and 16% produces single jersey. The figure reflects missing factories i.e. the factories were the information about their type of products is not available.

Missing

Single & Double & Ey 16.7%

25.0%

Single

Others 16.7% 4.2%

Double

37.5%

Figure 4.7: Type of knitted goods produced on local knitting factories

4.1.6.2 Production efficiency: The designed production capacity (target) for the surveyed local knitting factories is equal to 4712 tons of knitted goods per year as shown in Table 4.8. The actual production in year 1998 was 759 tons of knitted goods per year, about 16% whereas the actual production dropped to 302 tons in year 2005 even some new factories were introduced as shown in Table 4.8. This means that production in 2005 dropped to about 7% of the actual target capacity of the local industry.

- 70 - Table 4.8: Actual productions of knitted goods in local industry in ton

Tons/year Max Actual 1998 Actual 2005 Industry serial 1 194.00 - - 2 300.00 - - 3 216.00 43.00 - 4 - 6.00 0.16 5 50.00 48.00 15.00 6 90.00 72.00 - 7 216.00 43.00 18.00 8 720.00 360.00 6.00 9 48.00 12.00 24.00 10 48.00 - 24.00 11 60.00 54.00 - 12 54.00 42.00 4.80 13 12.00 7.00 1.80 14 36.00 18.00 2.60 15 29.00 18.00 6.00 16 36.00 - 9.00 17 36.00 18.00 - 18 240.00 - 144.00 19 18.00 18.00 - 20 29.00 - b22.00 21 1.44 - 1.00 22 28.80 - 5.40 23 90.00 - 18.00 24 - - - total 4712 759 302.00 Production % 100 16 7

4.1.7 Operating conditions and cleaning efficiency: 4.1.7.1 Operating conditions:

Only about 29% of the surveyed factories gave some care to relative humidity, about 21% of them gave more care including humidity and ventilation. While about 42% of the local knitting manufactures did not care about the environmental conditions as shown in Table 4.9.It was clearly illustrated in Fig. 4.8.

- 71 - Table 4.9: Type of facilities used in conditioning local knitting rooms Facility type No. of factories Percentage (%) Water Cooler 7 29 Air Condition 1 4 Exhaust Fan 1 4 Water cooler and Exhaust fan 5 21 None of mentioned 10 42 Total 24 100

Air Condition

4.2%

Exhaustion Fan

4.2% Water Cooler

29.2%

non

41.7%

w afan

20.8%

Figure 4.8: Available facilities used in conditioning knitting room

4.1.7. 2 Cleaning efficiency:

Regarding the cleaning efficiency, about 20.8% of the visited factories were clean and no waste yarns were observed on the floor. However in some factories, about 25%, fiber fly and accumulation of dust on the machines were observed as shown Table 4.10. From the table this information provided by 15 from 24 visited factories about 62.5% i.e. total valid. The information is not available for the nine factories about 37.5%, which were shown as missing in the table.

- 72 - Table 4.10: Cleaning efficiency of local knitting factories Cleaning measures No. factories Percentage (%) Dust on m/c 6 25.0 Waste Yarn 1 4.2 Fiber Fly 3 12.5 None of Mentioned 5 20.8 Total Valid 15 62.5 Missing 9 37.5 Total 24 100.0

- 73 - 4.2 Results of investigation of knitting parameters: 4.2.1 Results of investigation of initial setting of Terrot knitting machine: 4.2.1.1 Measured results of loop length and tension level at all feeders: The initial determined loop length and tension level at different feeders, numbered 1 to 16 are shown in Table 4.11. The machine operator who originally made the initial setting, assumed this initial setting as best condition for machine settings, as he previously used his fingers to regulate the tension levels and loop lengths. Naturally his behavior is subjective. The table also showed the adjusted scientific tension levels and uniform loop lengths. Table 4.11: Measured results of initial, adjusted loop length & tension level at different feeders st Initial Adjusted p loop length tension level loop length tension level fn in mm in cN≈ 1.02gm in mm in cN ≈ 1.02gm 1 6 5 5 5 2 6 5 5 5 3 7 7 5 5 4 6 7 5 5 5 5 8 5 5 6 3 7 5 5 7 4 6 5 5 8 3 7 5 5 9 7 8 5 5 10 6 5 5 5 11 7 10 5 5 12 7 10 5 5 13 8 5 5 5 14 8 5 5 5 15 8 5 5 5 16 5 6 5 5 Ave. 6 6 5 5 Whereas: st = setting type – p = parameter – fn = feeder number From the above Table 4.11 it can be observed that: i.The initial readings of loop length varied from feeder to feeder i.e. the equality in loop lengths for all feeders is not maintained. ii. Also the initial values of tensions vary from feeder to feeder and some feeders recorded high tension value, 10 cent Newton (cN), whereas the suitable tension for a knitting machine is equal to 5cN

- 74 - iii.The new adjusted values are uniform for both loop lengths & tension level. It is important to note that the adjustment of loop length was maintained at 5mm and the tension at 5cN. Following are the results of the quality tests for fabric samples produced by initial and readjusted setting of loop length and tension level:

4.2.1.2 Results of fabric quality tests by initial and adjusted loop length and tension setting: 4.2.1.2.1 Fabric structure for barakat and acala cotton yarns Ne 24/1 Following are the results of fabric structure i.e. wales (w) and courses (c) per cm which obtained by initial & adjusted settings of tension levels and loop length, from barakat and acala cotton yarns, Ne 24/1 1. Barakat cotton yarn Ne 24/1

i. Results of wales per cm It is clear from Table 4.12 that, there are slight differences in the results of meter-to- meter wales per cm, obtained by the two setting levels. Due to the effect of variation in tensions between feeders in initial setting, w/cm was varied in some meter of the fabric. The average values of w/cm are 8.0 & 8.3 for the initial and adjusted settings respectively. Constant w/cm was recorded from adjusted setting level (loop length and tension). Table 4.12: Measurements of fabric wales/cm (initial & adjusted setting, barakat)

sm 1 2 3 4 5 6 7 8 9 10 11 12 Ave. in 8.0 8.0 8.0 8.2 8.0 7.6 7.8 8.0 7.9 8.0 8.2 8.0 8.0 w/cm as 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 Where: sm = serial meters of fabric, w = wales per cm, as = adjusted setting, in = initial setting

The results of w/cm for both the setting levels were represented graphically against serial meters shown in Figure 4.9. From the figure, straight line was observed for the values of w/cm, obtained by the adjusted machine setting. Where an irregular line was observed for the values obtained by the initial machine setting.

- 75 - 8.4

8.2

8.0

w / cm 7.8 Setting type:

7.6 1-initial

7.4 2-adjusted 1 2 3 4 5 6 7 8 9 10 11 12

serial meter Figure 4.9: Wales/cm vs. serial meter for initial & adjusted setting, barakat

A paired sample test showed that the differences in w/cm, which were obtained by the initial and adjusted settings of loop length and tension are significant, sig. as p = 0.0 < 0.05, as shown in Table 4.13, with respect to values mentioned in section 3.3. It means that the differences in w/cm were not due to chance and constant w/cm was maintained by readjusted setting, the matter that improves the quality of the fabric. Table 4.13: Paired test for fabric wales/cm (initial & adjusted setting, barakat)

Paired Differences 95% Confidence interval t df Sig. Lower Upper (2tailed) initial-adjusted wales/cm -0.4268 -0.2232 -7.025 11 0.000

Whereas: t = t- test value, df = degree of freedom sig. = significant level .05

ii.Results of courses per cm It is observed from Table 4.14 that, the results of meter-to-meter courses per cm, obtained by initial setting, are different from those obtained by the adjusted setting. The average values of courses per centimeter, c/cm, for the initial and adjusted settings are 14.5 & 14.2 respectively. It is also observed that c/cm for adjusted setting are more regular than the former, except for the last two readings due to the regular tension. Table 4.14: Measurements of fabric courses/cm (initial & adjusted setting, barakat) sm 1 2 3 4 5 6 7 8 9 10 11 12 Ave in 14.6 14.5 14.2 14.2 14.3 14.6 14.7 14.7 14.8 13.9 14.2 14.6 14.4 c/cm as 14.2 14.2 14.2 14.2 14.2 14.2 14.2 14.2 14.2 14.2 14.4 14.4 14.2 Where: sm = serial meter, c/cm = courses per cm, as = adjusted setting, in = initial setting

- 76 - Similar to w/cm, the results of c/cm for the two setting levels were plot against serial meters as shown in Figure 4.10. It is clear from the figure; the graph obtained by adjusted setting level is more regular than the one obtained by the initial setting.

15.0

14.8

14.6

14.4

c / cm

14.2 Setting type:

14.0 2-adjusted

13.8 1-initial 1 2 3 4 5 6 7 8 9 10 11 12

serial meter

Figure 4.10: Courses/cm vs. serial meter for initial & adjusted setting, barakat

Table 4.15: Paired test for fabric courses/cm (initial & adjusted setting, barakat) Paired differences Confidence interval t df Sig. (2tailed) Lower Upper initial-adjusted courses/cm 0.0237 0.3930 2.483 11 0.030 Whereas: t = t- test value, df = degree of freedom sig. = significant level 0.05

From the above Table 4.15, a paired sample t-test showed that the differences in c/cm which were obtained by the initial and adjusted settings of loop length and tension are significant, sig. p = 0.03 < 0 .05 as mentioned earlier. It is therefore, clear there is real difference in courses per cm obtained by the two setting levels, which has to be rectified. 2. Acala cotton yarns Ne 24: i.Results of wales per cm From Table 4.16, there are considerable differences in the results of meter-to-meter wales per cm, obtained by the two setting levels. The average values of w/cm are 7.9 & 8.3 for the initial and adjusted settings respectively. Constant w/cm was recorded from adjusted setting level, the same as applied to barakat cotton yarn Ne 24 as above.

- 77 - Table 4.16: Results of fabric wales/cm (initial & adjusted setting, acala) sm 1 2 3 4 5 6 7 8 9 10 11 12 Ave in 7.8 7.8 7.7 7.8 8.0 8.0 7.8 7.8 8.0 8.0 7.9 7.7 7.9 w/cm as 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 Where sm = serial meter w = wales per cm, as = adjusted setting, in = initial setting The results of w/cm for both the setting levels are plotted against serial meters, shown in Figure 4.11. From the graph a straight line was observed for the w/cm, obtained by the adjusted loop length and tension levels. Where an irregular line was observed for the values of w/cm obtained by the initial loop length and tension levels in Terrot knitting machine setting.

8.4

8.3

8.2

8.1

8.0

w / w cm 7.9 setting type: 7.8 initial 7.7 7.6 adjusted 1 2 3 4 5 6 7 8 9 10 11 12

serial meter

Figure 4.11: Wales/cm vs. serial meter for initial & adjusted setting, acala From Table 4.17, the statistical paired test reflects that, the difference in w/cm that obtained by initial and adjusted setting levels is significant, at 95% confidence level, sig. p= 0.00 < 0.05.The result, is the same as when using barakat cotton yarn Ne 24/1.

Table 4.17: Paired test for fabric wales /cm (initial & adjusted setting, acala) Paired Differences 95% Confidence t df Sig. (2tailed) interval Lower Upper initial-adjusted wales/cm -0.5157 -0.3677 -13.138 11 0.000 Whereas t = t- test value, df = degree of freedom sig. = significant level 0.05

- 78 - ii.Results of courses per cm It is observed from Table 4.18 that, the results of meter-to-meter courses per cm, obtained by initial setting are different from those obtained by adjusted setting. The average values of c/cm for the both settings are 14.7 & 14.2 respectively. It is also observed that c/cm for adjusted setting is more regular than the former. Table 4.18: Measurements of fabric courses/cm (initial & adjusted setting, acala) sm 1 2 3 4 5 6 7 8 9 10 11 12 Ave in 14.2 14.6 14.7 14.7 14.7 14.7 15.2 14.8 14.7 14.7 14.7 15.2 14.7 c/m as 14.2 14.2 14.2 14.4 13.8 14.2 14.2 14.2 14.2 14.2 14.2 14.2 14.2 Where sm = serial meter, c= courses per cm, as= Adjusted setting, in = initial setting

Figure 4.12 shows the plots of c/cm against serial meters. From the figure, the graph obtained by initial c/cm is irregular compared to one obtained by adjusted c/cm. It was similar to the Figure 4.10 that plots of barakat cotton yarns.

15.4

15.2

15.0

14.8

14.6

c / cm 14.4

14.2 Setting type: 14.0 1-initial 13.8 13.6 2-adjusted 1 2 3 4 5 6 7 8 9 10 11 12

serial meter

Figure 4.12: Courses/cm vs. serial meter for initial & adjusted setting, acala

From Table 4.19, the statistical paired test reflects that, the difference in courses per cm obtained by initial and adjusted setting levels is significant at 95% confidence level, as p = 0.00 and < 0.05. This is similar to the results obtained by using barakat cotton yarn. Table 4.19: Paired test for fabric courses/cm (initial & adjusted setting, acala) Paired Differences 95% Confidence interval t df Sig. (2tailed) Lower Upper initial-adjusted courses/cm 0.3633 0.7367 6.483 11 0.000 Whereas t = t- test value, df = degree of freedom sig. = significant level 0.05

- 79 - It was observed also that knitting parameters, wales and courses per cm affect each other. As the wales per cm, w/cm, increased in the new adjusted setting of the loop length and tension levels, the courses per cm, c/cm, on other hand have decreased. The average value of w/cm was increased from 8.0 to 8.3 w/cm (Table 4.2) and the average value of c/cm was decreased from 14.6 c/cm to 14.2 c/cm (Table 4.4) when using barakat cotton yarn. The same phenomenon was observed when using acala cotton yarn, the average value of w/cm was increased from 7.9 to 8.3 w/cm (Table 4.6) and the average value of c/cm was decreased from 14.7 to 14.2 c/cm (Table 4.8). This is due to knitting machine design, i.e. the w/cm are governed by the machine gauge. Therefore knitted fabric structure, like other engineering structure or material, can be measured for dimensions (wales and courses) during its production, by adjusting loop length and tension and accordingly the knitting performance. 4.2.1.2. 2 Results of fabric width and shrinkage for barakat and acala cotton yarns Ne 24.1: 1. Barakat cotton yarn Ne 24/1: Table 4.20: Results of fabric width & shrinkage (initial & adjusted setting, barakat) sm 1 2 3 4 5 6 7 8 9 10 11 12 Ave in 84.8 84.8 84.8 84.8 84.3 84.3 84.3 83.8 84.3 84.3 83.8 83.8 84.1 Width cm as 86.2 86.2 86.2 86.2 86.2 86.2 86.2 86.2 86.2 86.2 86.2 86.2 86.2 in 50.9 50.9 51.9 51.9 51.4 51.4 51.4 51.9 51.4 51.9 51.9 51.9 51.6 Shrink cm As 53.1 53.1 53.1 53.1 53.1 53.1 53.1 53.1 53.1 53.1 53.1 53.1 53.1 Where sm = serial meter, as = adjusted setting, in = initial setting

The above Table 4.20 shows the results of knitted fabric width and the calculated shrinkages measured in centimeters. The shrinkage is calculated from the fabric width away from the machine. The fabric samples are produced from barakat cotton yarn, Ne 24. Clear difference on fabric width and shrinkage was observed between the fabrics obtained by initial machine settings, namely 84.1 and 51.9 cm respectively, and the one obtained by adjusted settings 82.6 and 53.1cm. The graphical plots, Figure 4.13, showed the differences in fabric widths along the fabric length indicating a better quality (consistency on fabric width) by the adjusted setting.

- 80 - 85.0

84.5

84.0

83.5

width in cm 83.0 Seting type:

82.5 1-initial

82.0 2- adjusted 1 2 3 4 5 6 7 8 9 10 11 12

serial meter

Figure 4.13: Fabric width vs. serial meter for initial & adjusted setting, barakat

Pair statistical analysis on Table 4.21 showed significant difference between the values of the fabric width obtained by the two different settings, sig. p = 0.00 < 0.05. The confidence interval limits 1.3 to1.8 do not include zero. This is mainly due to different in number of wales per cm, as was observed in previous results of fabric structure

Table 4.21: Paired test for fabric width and shrinkage (initial & adjusted setting, barakat) Paired Differences 95% Confidence t df Sig. interval (2tailed) Lower Upper width initial – adjusted setting 1.2860 1.7807 13.646 11 0.000 shrink initial - adjusted setting -1.7807 -1.2860 -13.646 11 0.000 Whereas t = t- test value, df = degree of freedom sig. = significant level 0.05

- 81 - 2. Acala cotton yarns Ne 24:

Table 4.22 shows the results of knitted fabric width and the shrinkages measured in centimeters. The fabric samples were produced from acala cotton yarn, Ne 24. Clear differences on fabric width and shrinkages were observed between the fabrics obtained by initial machine setting, 84.3 cm in width and 51.4 cm shrinkage, and the one obtained by adjusted setting 82.9 and 52.8 cm respectively.

Table 4.22: Results of fabric width and shrinkage (initial & adjusted setting, acala) sm 1 2 3 4 5 6 7 8 9 10 11 12 Ave. Width in 84.3 84.3 84.3 84.3 84.3 84.3 84.3 84.3 84.8 84.8 83.8 83.8 84.3 cm as 83.3 82.8 82.8 82.8 82.8 82.8 82.8 83.3 82.8 82.8 82.8 82.8 82.9 Shrink in 51.4 51.4 51.4 51.4 51.4 51.4 51.4 51.4 50.9 50.9 51.9 51.9 51.4 cm as 52.4 52.9 52.9 52.9 52.9 52.9 52.9 52.4 52.9 52.9 52.9 52.9 52.8 Where -sm = serial meter, in = initial setting, as= adjusted setting

85.0

84.5

84.0

83.5

width in cm Setting type:

83.0 1-initial

82.5 2- adjusted 1 2 3 4 5 6 7 8 9 10 11 12

serial meter

Figure 4.14: Fabric width vs. serial meter for initial & adjusted setting, acala

Figure 4.14 above shows the plots of the fabric width obtained by initial and adjusted settings of loop length and tension. From the figure, the plotted graph of adjusted setting is more regular than the plot of initial setting and only two readings are different.

- 82 - Pair statistical analysis on Table 4.23 showed significant differences between the values of the fabric widths obtained by the two different settings, sig. p = 0.00 and < 0.05. This is mainly due to difference in number of wales, as was observed in previous results of fabric structure. Table 4.23: Paired test for fabric width and shrinkage (initial & adjusted setting, acala) Paired Differences 95% Confidence interval t df Sig. (2tailed) Lower Upper Pair1 width initial – adjusted setting 1.1887 1.6447 13.675 11 0.000 Pair2 shrink initial - adjusted setting -1.6447 -1.1887 -13.675 11 0.000 Where: t=t-test, df=degree of freedom, sig.=significant level at .05 4.2.1.2. 3 Measurement of fabric gsm for barakat and acala cotton yarns Ne24: 1. Bearcat cotton yarn Ne 24: Table 4.24: Results of fabric gms (initial & adjusted setting, barakat) sm 1 2 3 4 5 6 7 8 9 10 11 12 Ave in 166.0 166.0 165.0 168.0 165.0 162.0 167.0 161.0 170.0 171.0 172.4 175.6 167.4 gms as 163.0 168.5 165.0 170.6 164.0 158.9 168.0 163.0 169.0 166.0 166.5 166.5 165.4 Whereas: sm = serial meter, gms = grams per square, as= adjusted setting, in = initial setting

Table 4.24 gives the fabric weight per square meter samples from barakat cotton yarn Ne 24\1. There is some interference between the values obtained by the two settings i.e. initial & adjusted. Likewise small differences in average values of fabric weight namely 167.4 and 165.4 gm/sq were observed the result of effect of un-equal tensions in the two settings. The results of fabric weight per square meter obtained by the two setting levels were represented graphically in Figure 4.15. From the figure, approximately the two plots are similar.

- 83 - 180

170

gm / sqm 160 setting ty pe:

1-initial

150 2- adjusted 1 2 3 4 5 6 7 8 9 10 11 12

serial meter

Figure 4.15: Gms vs serial meter for initial & adjusted setting, barakat

The pair statistical test showed that, the differences, in fabric weight per square meter (gms), obtained by the two setting levels, are not significant, where sig. p = 0.136 > 0.05, the confidence interval limit, 0.007 to 0.04, includes zero. It was shown in Table 4.25. However, it is noted that, the differences in loop length and tension in this experiment do not affect the fabric weight per square meter greatly.

Table 4.25: Paired test for fabric gms (initial & adjusted setting, barakat) Paired Differences 95% Confidence interval t df Sig. (2tailed) Lower Upper Pair initial – adjusted gms -0.006445 0.041279 1.606 11 0.136 Where: t=t-test, df = degree of freedom, sig. =significant level at .05 2. Acala cotton yarn Ne 24: Table 4.26 shows the fabric weight per square meter for samples from acala cotton yarn Ne 24. There is some interference between the values obtained by the two settings i.e. initial & adjusted. Nevertheless, the differences between the values obtained by the two setting levels are small; the average values are 171.9 and 172 gm for initial and adjusted settings respectively.

- 84 - Table 4.26: Measurements of fabric gsm (initial & adjusted setting, acala) sm 1 2 3 4 5 6 7 8 9 10 11 12 Ave in 172.0 180.0 169.0 173.0 165.0 172.0 173.0 163.0 173.0 172.0 173.0 176.0 171.9 gms as 166.0 173.0 175.0 176.0 175.0 169.0 173.0 168.3 175.0 175.0 170.0 172.0 172.0 Whereas: sm= serial meter, gms= grams per square meter, as= adjusted setting, in= initial setting

The above results are similar to the previously obtained results when using barakat cotton yarn Ne 24. Again, the results of fabric weight per square meter obtained by both setting levels, were illustrated graphically in Figure 4.16. From the figure, the two plots nearly show similar curve.

178

176

174

172

gm/sqm 170

168 Setting type:

166 1- initial

164 2-adjusted 1 2 3 4 5 6 7 8 9 10 11 12

serial meter

Figure 4.16: Gms vs. serial meter for initial & adjusted setting, acala

Table 4.27 shows the pair statistical test, for the differences in fabric weights per square meter obtained by the two setting levels. From the table, similar to results obtained by using barakat yarn Ne 24, the difference, by using acala cotton yarn Ne 24 is not significant, as sig. p = 0.812 > 0.05, the values of confidence interval limit are 0.04 to 0.03 include zero. The differences in loop length and tension in this experiment do not affect the fabric weight per square meter greatly. Table 4.27: Paired samples test for fabric gm/sqm (initial & adjusted setting, acala) 95% Confidence interval Paired Differences t df Sig. (2tailed) Lower Upper Pair initial – adjusted gm \ sqm -0.036001 0.028834 -0.243 11 0.812 Where: t=t-test, df=degree of freedom, sig.=significant level at .05

- 85 - 4.2.1.2.4 Fabric extensibility for barakat and acala cotton yarns Ne 24: 1. Barakat cotton yarn Ne 24: Table 4.28: Results of fabric extensibility % for fabric (initial & adjusted setting, barakat) sm 1 2 3 4 5 6 7 8 9 10 11 12 Ave.

Ext in 164 160 165 155 140 130 160 170 170 165 160 165 159 % as 197 197 186 193 195 200 170 172 175 180 178 180 185

Rec in 82 82 70 65 65 60 97 95 95 92 92 92 82 % as 85 61 95 95 74 85 130 120 125 125 115 130 103 Where: sm = serial meter, ext. = extension, rec = recovery, in = initial, as= adjusted setting

Clear differences were found in values of fabric extensibility, extension and recovery, for the samples obtained by initial and adjusted setting of loop length and tension as shown in Table 4.28 above. From the table a high extensibility percentage was obtained by the new adjusted setting. The average values of extension percentage for initial and adjusted setting levels are 159 and 185 respectively. Similarly, the average values of recovery percentage are 82 and 103 respectively. Graphically, Figure 4.17 a, b shows that each time; the graphs produced by adjusted values are on top of the figures produced by initial one. It was observed that fabric structure obtained by readjusted setting was more regular than the structure obtained by initial setting.

- 86 - 220 140

200 120

180 100

recvery % 80 160

extension % extension seting type : setting type: 60 140 1-initial 1-initial 40 2-adjusted 120 2-adjusted 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 serial meter serial meter b a

Figure 4.17: Fabric extensibility vs. serial meter for initial & adjusted setting, barakat, where: a) Extension (%) b) Recovery (%)

Paired statistical tests showed a significant difference between the results obtained by the two setting levels as shown in Table 4.29.That is for both parameters: extension and recovery percentages. Unlike knitted fabric weight per square meter, the values of fabric extension and recovery percentages which were obtained by the two setting levels are statistically different and it is significant since p = 0.001 and < 0.05 and confidence interval limits are 39.7 to 13.5 not including zero.

Table 4.29: Paired test for fabric extensibility % (initial & adjusted setting, barakat) 95% Confidence interval Paired Differences t df Sig. (2tailed) Lower Upper 1 initial – adjusted extension% -39.70 -13.46 -4.459 11 0.001 2 initial – adjusted recovery% -31.62 -10.55 -4.406 11 0.001 Where: t = t-test, df = degree of freedom, sig. = significant level at .05

2. Acala cotton yarns Ne 24: A clear difference was found in values of the fabric extensibility (%) for the samples obtained by initial and adjusted settings of loop length and tension level shown in Table 4.30. From the table a high extensibility percentage was obtained by the new adjusted setting. The

- 87 - average values of extension (%) for initial and adjusted setting levels are 150 and 194 respectively. In addition, the average values of recovery % which were obtained by the tow setting levels are 76 and 125 respectively. This was similar to the results obtained by use of the barakat cotton yarn.

Table 4.30: Measurements of fabric extensibility % (initial & adjusted setting, acala) Sm 1 2 3 4 5 6 7 8 9 10 11 12 Ave. Ext in 155 166 150 160 160 155 160 160 160 165 170 155 150 % as 190 180 190 195 190 192 205 200 205 205 187 190 194 Rec in 60 67 65 65 55 55 97 105 95 95 90 60 76 % as 130 105 106 105 100 106 150 135 145 160 132 125 125 Whereas: sm = serial meter, ext. = extension, rec = recovery, in = initial, as = adjusted setting

Graphically, Figure 4.18 shows that each time the graphs produced by adjusted values are on top of the figure of initial one i.e. high values of extensibility. Similar to barakat the fabric structure obtained by readjusted setting was more regular than the structure obtained by initial setting.

210 180

200 160

190 140

180 120

170 100

recovery %

extension %

160 Setting type: 80 Setting type:

1-initial 150 1-initial 60

140 2-adjusted 40 2-adjusted 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12

serial meter serial meter

a b Figure 4.18: Fabric extensibility vs. serial meter for initial & adjusted setting, acala barakat, where: a) Extension (%) b) Recovery (%)

Paired statistical tests showed a significant difference between the results obtained by the two setting levels as shown in Table 4.31.That is for both parameters: extension and recovery percentages, as significant level p = 0.00 and < 0.05, interval limit 40.7 to 28.2 not including zero. According to statistical significant mentioned in chapter 3.3.

- 88 -

Table 4.31: Paired test for fabric extensibility % (initial & adjusted setting, acala) Paired Differences 95% Confidence Interval of df Sig. (2- tailed) the Difference

Lower Upper 1 initial – adjusted extension -28.17 -12.117 11 0.000 2 initial – adjusted recovery -41.47 -13.809 11 0.000 Where: t = t-test, df = degree of freedom, sig. = significant level at 0.05

4.2.1.2.5 Results of fabric pilling for barakat and acala cotton yarns Ne 24.1: No positive results were obtained from pilling tests, because of failure in pilling testers. Both instruments in T.T.L, UG (textile testing Laboratory University of Gezira), and IRCC (Industrial Research and Consultancy Center) are old. Even after repairing the electrical side of the pilling tester in (IRCC) no positive results were obtained, because of the bad internal coating of the drum.

- 89 - 4.2. 2 Investigation of adjusted different loop lengths: 4.2.2.1 Results of fabric quality tests: 4.2.2.1.1 Fabric structure: Table 4.32 shows the results of effect of adjusted different loop lengths on wales/cm (w/cm). The w/cm remained constant with the increasing in loop length; the average values of w/cm are 8.7, 8.7 and 8.7 corresponding to loop lengths 5, 16 and 28 mm respectively.

Table 4.32: Measurement of fabric structure by varying loop length for barakat cotton yarn Ne 36 structure Courses/cm Wales/cm Serial meter L 5 16 28 5 16 28 1 13.3 12.1 11.3 8.7 8.7 8.7 2 13.4 11.8 11.4 8.7 8.7 8.7 3 13.4 11.9 11.4 8.7 8.7 8.7 4 13.4 11.8 11.4 8.7 8.8 8.7 5 13.4 11.8 11.4 8.7 8.7 8.5 6 13.4 11.8 11.3 8.6 8.7 8.7 7 13.4 11.8 11.4 8.7 8.7 8.7 8 13.4 11.8 11.4 8.6 8.5 8.7 9 13.4 11.8 11.4 8.7 8.7 8.7 10 13.4 11.9 11.4 8.7 8.7 8.7 11 13.4 11.9 11.4 8.6 8.7 8.7 12 13.6 11.8 11.4 8.7 8.7 8.7 Ave. 13.4 11.9 11.4 8.7 8.7 8.7 Whereas: L = loop length in mm

Table 4.32 also shows the results of effect of adjusted loop lengths on c/cm. From the table it is observed that the c/cm decreased with increasing loop lengths while average values of c/cm obtained by the three settings of loop length are equal to 13.4, 11.9 and 11.4 respectively. In other words, with short loop length the c/cm is high, while wales w/cm are constant. With long loop length, the c/cm is small. At a fixed distance, such as 1 cm, short courses are greatest than long courses. This is a phenomenon along of the loop length.

- 90 - It is clearly illustrated in Fig. 4.19 a, b: that the plot obtained straight line a of wales per cm against loop length. While the plot b of courses per cm against loop length resulted in inverse curve. Increasing in loop length caused reduction in number of courses per cm.

9 14.0

13.5

13.0

8 12.5

wales per cm per wales courses per cm per courses 12.0

11.5

7 11.0 5 16 28 5 16 28

loop length loop length

a b Figure 4.19: Effect of loop length on fabric structure for barakat cotton yarn Ne.36, where:

a) Wales per cm b) Course per cm

The data was analyzed by SPSS program to utilize relations and establish formulae. High inverse correlation coefficient, (-.9), was observed between loop length and courses per cm, significant at .01 level p = 0 .000 and < 0.01 as shown in Table 4.33. From the same table a low correlation coefficient (≈0.06) was observed between wales/cm and loop length and not significant at 0.01 level p = 0.733 and > 0.01. It is according to statistical values mentioned in section 3.3 Table 4.33: Correlation test of w/cm & c/cm against loop length for barakat yarn Ne.36 courses per loop length wales per cm cm loop length Pearson Correlation 1 0.059 -0.944** Sig. (2-tailed) - 0.733 0.000 ** Correlation is significant at the 0.01 level (2-tailed)

- 91 - By using statistical regression test, as shown in Table 4.34, the equation constant A, and regression coefficient B, were obtained. By simulating general linear regression formula -1, simple regression equation -2 was established. Eqution-2 enabled us to regulate the number of courses per centimeter by adjusting the loop lengths in millimeters. Equation-1 is true for values of loop lengths between 5mm and 28mm. 푌 = 퐴 + 퐵 × 푋 ------1 Courses = 13.64 – 0.1×loop length-----2 Table 4.34: regression coefficients for fabric courses against loop length

Variable formula Rsq d.f. F Sig. A B courses linear 0.892 34 280.17 0.000 13.6398 -0.0873 wales ------Whereas: Rsq =R square, d.f. =degree of freedom, sig. = significant level, A& B are equation constant

4.2.2.1.2 Fabric width: The results of fabric width, obtained by different loop lengths, were shown in Table 4.35. The average values decreased with increasing in loop length. Due to the reduction in courses per cm, which observed in Table 4.32, refers to section 4.2.2.1.1, the fabric width affected too. The values of fabric shrinkage increased with increasing in loop lengths have been shown in same Table 4.35. Table 4.35: Measurement of fabric width produced by varying loop lengths property width shrink

Serial meter L 5 16 28 5 16 28 1 77.7 77.5 76.7 58 58.2 59.7 2 77.7 77.5 76.7 58 58.2 59.7 3 77.7 77.5 77.2 58 58.2 58.5 4 77.7 77.5 77.2 58 58.2 58.5 5 77.7 77.5 77.2 58 58.2 58.5 6 77.7 77.5 77.2 58 58.2 58.5 7 77.7 77.5 77.2 58 58.2 58.5 8 77.7 77.5 77.2 58 58.2 58.5 9 77.7 77.5 77.2 58 58.2 58.5 10 77.7 77.5 77.2 58 58.2 58.5 11 77.7 77.2 77.2 58 58.5 58.5 12 77.7 77.2 77.2 58 58.5 58.5 Ave. 77.7 77.5 77.1 58 58.3 58.7 Whereas L = loop length in mm

- 92 - The correlation test between fabric width and loop length gave negative high value (- 0.88), significant at 0.01 as shown in Table 4.36 i.e. strong inverse relation between fabric width and loop length. From the same table correlation coefficient was positive (0.88) and significant at 0.01 level for the relation between loop length and fabric shrinkage.

Table 4.36: Correlations test for fabric width against loop length, barakat cotton yarn Ne 36 loop length fabric width fabric shrink loop length Pearson Correlation 1 -0.883** 0.884** Sig. (2-tailed) . 0.000 0.000 ** Correlation is significant at the 0.01 level (2-tailed)

The results of fabric width and shrinkage are illustrated in Figure 4.20. From the figures, it is clear that the curve a obtained for fabric width is inversely related to loop length, while the shrink curve b is positively related to loop length. Increasing loop length makes fabric less compact the manner, which provides more extension.

80 80

75 75

70 70

65 65

fabric width in cm in fabric width 60 fabric shrink incm fabric shrink 60

55 55

Rsq = 0.9991 50 50 0 5 10 15 20 25 30 Rsq = 0.9998 0 5 10 15 20 25 30 loop length in mm loop length i mm a b Figure 4.20 a, b: Effect of loop length on fabric width and shrink for barakat cotton yarn Ne.36, where: a) Fabric width in cm b) Fabric shrink in cm

By using statistical regression test, equation constant A, and regression coefficients B and C, were obtained as shown in Table 4.37. The statistical significant and correlation coefficient were accepted with respect to values mentioned in chapter 3.3. By using standard

- 93 - quadratic formula-3, a formula-4 was established for calculating fabric width by knowing the loop length. The formula is valid for loop lengths between 5mm and 28mm. Y = A + B × X + C × X² ------3 Width = 72.45 + 1.38 × loop - 0.07 × loop length² ----4

Table 4.37: Regression coefficients for fabric width & shrink against loop length Variable formula Rsq d.f. F Sigf A B C linear 0.780 34 120.74 0.000 84.958 -0.837 Width quadratic 0.999 33 18444.40 0.000 72.458 1.383 -0.067 linear 0.781 34 121.08 0.000 50.597 0.842 Shrink quadratic 1.000 33 84028.90 0.000 63.276 - 1.392 0.067 Whereas: Rsq = R square, d.f. = degree of freedom, sig. = significant level, A, B & c are equation constants & regression coefficient respectively

4.2.2.1. 3 Fabric weight: Table 4.38 represents the results of knitted fabric weights produced by using different loop lengths. The average values are equal to 109.7, 105.3 and 102.2 were increased with decreasing in loop lengths 5, 16 & 28 respectively. Table 4.38 Measurement of fabric gms by different loop lengths (L) Property Gms

Serial meter L mm 5 16 28 1 108.4 103.3 100.6 2 109.0 104.5 102.6 3 109.0 103.9 101.4 4 107.6 105.7 101.6 5 106.6 111.1 103.2 6 109.9 106.0 101.4 7 110.1 105.1 103.9 8 110.1 105.2 102.0 9 110.5 104.5 103.4 10 111.3 105.6 101.7 11 114.0 104.0 102.0 12 110.0 105.1 103.1 Ave. 109.7 105.3 102.2

- 94 - Significant negative correlation, -0.879, was found between loop length and fabric weight per square meter, as shown statistical Table 4.39. In other words increasing the loop length will cause decreasing in fabric weight per square meter.

Table 4.39: Correlation test for gms and loop length, barakat cotton yarn Ne.36 /1 loop length fabric gms loop length Pearson Correlation 1 -0.879** Sig. (2-tailed) . 0.000 ** Correlation is significant at the 0.01 level (2-tailed)

The results of fabric weights produced by different loop lengths were illustrated in Figures 4.21. From the figure, the relation is clear, the fabric weight decreases with increasing loop length.

110

108

106

gm / sqm 104

102

100 5 16 28

loop length Figure 4.21: Effect of varying loop length on fabric weight for barakat cotton yarn Ne.36

By applying statistical regression test, equation constant, A, and regression coefficient, B, were obtained as shown in Table 4.40. Simulating standard formula-1, formula-5 was established to estimate knitted fabric weight regulating loop lengths. The formula-5 is true for loop lengths between 5 mm & 28 mm. 푌 = 퐴 + 퐵 × 푋 ------1 Gms = 111.05 – 0. 32 × loop length---5 Table 4.40: Regression coefficients of fabric gms against loop length Variable formula Rsq d.f. F Sigf A B C weight linear 0.772 34 115.18 0.000 111.047 -0.3236 - quadratic 0.784 33 59.92 0.000 112.184 -0.5256 0.0061 Whereas Rsq =R square, d.f.=degree of freedom, sig. = significant level, A& B are equation constant

- 95 - 4.2.2.1.4 Fabric extensibility: Table 4.41 shows fabric extension and recovery values that were produced by varying loop lengths. From the table the average results vary between, 248.8, 271 & 285 (%), respectively corresponding to namely short 5, medium 16 and long 28 mm loop lengths.

Table 4.41 Measurements of fabric extension and recovery by varying loop length property Extension % Recovery %

Serial meter L 5 16 28 5 16 28 1 261 270 288 175 220 214 2 261 264 282 170 195 230 3 245 285 280 170 230 232 4 244 260 290 173 170 205 5 256 265 284 178 175 190 6 255 275 286 188 185 230 7 245 280 283 194 235 240 8 247 270 283 190 240 240 9 242 275 285 192 220 245 10 240 270 290 192 210 245 11 245 270 286 193 215 240 12 245 273 287 190 205 235 Ave. 248.8 271 285 183 208 229

From same Table 4.41 the averages values of recovery: 183, 208 and 229 were vary from short loop length, medium and high, respectively. Appositive correlation was observed for both extensions and recoveries; .0.92 & 0.7 respectively, significant at .01 level, for short, medium and long loop lengths as shown Tables 4.42.

Table 4.42: Correlations test for extension and recovery against loop length loop length fabric extension fabric recovery loop length Pearson Correlation 1 0.920** 0.738** Sig. (2-tailed) . 0.000 0.000 ** Correlation is significant at the 0.01 level (2-tailed).

- 96 - The result of fabric extension and recovery, which were obtained by varying loop lengths are represented graphically in Figure 4.22. It is clear from the graph that fabric extensibility increases with the increasing in loop length

300

280

260

Extensibility 240 Recovery Extension 220

extensibility % 200

180 reccowery %

160 extension % 5 16 28

loop length in mm

Figure 4.22: Effect of loop lengths on fabric extensibility

From Table 4.43 the equation constant A, regression coefficients B and C, were obtained. Simulating standard quadratic formula: 3, Equation: 6 was established. Equation: 6 is valid for values of loop lengths from 5mm to 28mm to estimate extension % for knitted fabrics. Y = A + B×X + C×X² ---3 Extension = 235.5 + 2.9×loop length – 0.04×loop length² ----6

Table 4.43: Regression coefficients for fabric extension and recovery against loop length Variable Mathematical formula Rsq d.f. F Sigf A B C extension quadratic 0.869 33 109.85 0.00 235.461 2.8687 -0.0388 recovery quadratic 0.548 33 20.00 0.00 170.744 2.7156 -0.0229 Whereas: Rsq =R square, d.f. =degree of freedom, sig. = significant level, A & B are equation constant

- 97 - 4.2.3 Investigation of effect of different yarn counts Ne on knitting performance: 4.2.3.1 Results of fabric quality tests:

Following are the results of fabric quality tests for the samples produced from different barakat cotton yarn counts namely, Ne 36, 30 and 24. 4.2.3.1.1 Fabric structure: Table 4.44: Results of fabric structure by different yarn counts property courses wales Serial Ne meter 36 30 24 36 30 24 1 13.3 13.4 13.9 8.7 8.3 8.3 2 13.4 13.4 14.2 8.7 8.3 8.3 3 13.4 13.4 14.2 8.7 8.3 8.3 4 13.4 13.4 14.2 8.7 8.3 8.3 5 13.4 13.4 14.2 8.7 8.3 8.3 6 13.4 13.4 14.2 8.6 8.3 8.3 7 13.4 13.4 14.2 8.7 8.3 8.3 8 13.4 13.4 14.2 8.6 8.3 8.3 9 13.4 13.4 13.8 8.7 8.3 8.3 10 13.4 13.4 14.2 8.7 8.3 8.3 11 13.4 13.4 14.2 8.6 8.7 8.7 12 13.6 13.4 14.1 8.7 8.3 8.3 Ave. 13.4 13.4 14.1 8.7 8.3 8.3

Table 4.44: gives the results of courses and wales per cm for fabric samples produced from different barakat cotton yarn counts Ne: 36, 30 and 24. The c/cm obtained by Ne 24, equals 14.1 c/cm, was considerably higher than those obtained by Ne 30 and Ne 36, 13.4 c/cm. While no differences were observed between the values of c/cm obtained by Ne 30 and Ne 36, refers to both average values 13.4, 13.4. The values of wales per cm, for Ne 24 and 30 about 8.3 w/cm. The average value of w/cm, 8.7 obtained by Ne 36 is slightly different from w/cm, 8.3, obtained by Ne 30 and 24 as shown in the above table.

- 98 - Table 4.45: Correlation test for fabric structure against yarn count Ne. 36, 30 and 24 count Ne course per cm wales per cm count Ne Pearson Correlation 1 -0.849** 0.749** Sig. (2-tailed) . 0.000 0.000 ** Correlation is significant at the 0.01 level (2-tailed)

According to statistical significant values in section 3.3, a high negative correlation, - 0.849**, between yarn counts (Ne) and c/cm was observed and it is sig. p=.000 and < .01 levels, mentioned in section 3.3as shown in Table 4.45 above. The table also showed that positive correlation, 0.749**, was obtained between w/cm and yarn counts (Ne).The table also showed a weak negative relation between c/cm and w/cm, -0.421* but it is statistically significant at .05 level.

14.0 8.8

13.9 8.7 13.8

13.7 8.6

13.6 8.5 13.5

course per cm

wales per cm 13.4 8.4

13.3 8.3 13.2 24 30 36 8.2 24 30 36 y arn count Ne

y arn count Ne

a b Figure 4.23: Effect of different yarn counts on fabric structure, where:

a) Course per cm b) Wales per cm

The relation between yarn counts and fabric structure is almost linear represented by Figure 4.23a, b above. The figure showed that the c/cm remained almost constant, from Ne 36 to 30, and increased at Ne 24. The opposite of this phenomenon was observed on w/cm.

- 99 - By applying statistical regression test, equation constant A, and regression coefficient, B, were obtained see Table 4.46. By using standard linear formula 1, equations 7 & 8 were established to estimate fabric structure by knowing yarn count Ne. 푌 = 퐴 + 퐵 × 푋 ------1 Course/cm = 15.46 - .06 × Ne------7 Wales/cm = 7.59 +.03 × Ne------8

Table 4.46 Regression coefficients for fabric structure against yarn Ne.36 /1, 30/1, 24/1 Variable Mathematical formula Rsq d.f. F Sigf A B courses linear 0.720 34 87.53 0.000 15.467 -0.0611 wales linear 0.560 34 43.35 0.000 7.590 0.0285 Whereas: Rsq = R square, df = degree of freedom, Sig = significant level A& B are equation constants 4.2.3.1.2 Fabric width: Table 4.47 Measurement of fabric width (cm) against yarn counts Ne property Width (cm) Serial meter Ne 36 30 24 1 77.7 78 82.6 2 77.7 78 82.6 3 77.7 78 82.6 4 77.7 78 82.6 5 77.7 78 82.6 6 77.7 78 82.6 7 77.7 78 82.6 8 77.7 78 82.6 9 77.7 78 82.6 10 77.7 78 82.6 11 77.7 78 82.6 12 77.7 78 82.6 Ave. 77.7 78 82.6

Table 4.47 above gives the values of the fabric width measured in cm. The average values are 77.7, 78 & 82.6 cm corresponding to counts 36, 30 and 24 Ne, respectively. Light decreasing in width from count 36 to 24 Ne, only 1.7cm. While greater decreasing in width is observed from count 30 to 24 about 4.6 cm. The fabric width is affected by yarn fineness i.e. yarn diameter. In addition, statistical correlation test, showed inverse high correlation

- 100 - coefficient approximately (-0.9) between fabric width and yarn counts Ne, as shown in the following Table 4.48.

Table 4.48: Correlation test for fabric width against yarn counts Ne. 36, 30& 24 count Ne fabric width in cm count Ne Pearson Correlation 1 0.892** Sig. (2-tailed) . 0.000 ** Correlation is significant at the 0.01 level (2-tailed).

The results were illustrated graphically in Figure 4.24. From the figure, a linear curve was observed showing increasing in fabric width with reduction in yarn counts Ne i.e. coarse count.

83

82

81

80

79

fabric width in cm

78

77 24 30 36

y arn Ne

Figure 4.24: Effect yarn count on fabric width

By applying regression statistical test, the values of equation constant, A, and coefficient, B were calculated as shown in Table 4.49. Simulating standard formula 1, equation 9; was established to estimate fabric width by knowing yarn count. Equation 9 is approximately true for yarn counts: 36, 30, and 24. The calculated shrink values showed the same phenomenon, higher shrink % was observed with low counts. As mentioned in section 3.2.3.1, fabric shrink was calculated from fabric width and machine circumference.

푌 = 퐴 + 퐵 × 푋 ------1 Width = 91.6 - .41 × Ne ------9

- 101 - Table 4.49 Regression test for fabric width against yarn count Ne: 36, 30, 24 variable formula Rsq d.f F Sigf A B width linear 0.796 34 132.45 0.000 91.68 -0.41 Whereas Rsq=R square, df=degree of freedom, Sig =significant level A& B are equation constant

4.2.3.1.3 Fabric weights in grams per square meter:

Table 4.50 above gives the results of weights in gram per square meter for knitted fabrics made from different barakat cotton yarn counts Ne: 36, 30 and 24. It is clear from the table that the average values of fabric weights 109.7, 135.2 and 171.1 were increased with decreasing yarn counts, Né: 36, 30 and 24 respectively. Obviously, this reflects the yarn phenomenon. The finer yarn produces lighter fabric. It means that Yarn fineness affects fabric weight.

Table 4.50: Results of fabric gms for different yarn counts Ne property gms Serial meter Ne 36 30 24 1 108.4 138.0 165.5 2 109.0 138.0 173.4 3 109.0 136.0 174.5 4 107.6 137.0 175.6 5 106.6 136.0 174.9 6 109.9 135.0 163.2 7 110.1 130.0 173.3 8 110.1 133.0 163.8 9 110.5 133.0 174.5 10 111.3 130.0 175.2 11 114.0 138.0 165.5 12 110,0 138.0 173.4 Ave. 109.7 135.2 171.1

The results are illustrated graphically in Figure 4.25. From the Figure, The relation between the fabric weight and yarn count is linear.

- 102 - 170

160

150

140

130

gm / sqm

120

110

100 24 30 36

y arn count Ne

Figure 4.25: Effect of different yarn counts on fabric weight gm/sqm

Table 4.51: Correlation test for fabric weight against yarns Ne 36, 30, 24

count Ne weight per sqm count Ne Pearson Correlation 1 -0.996** Sig. (2-tailed) . 0.000 ** Correlation is significant at the 0.01 level (2-tailed).

Extreme negative correlation value was observed between fabric weight per square meter and yarns counts the correlation coefficient is approximately (1) as shown Table 4.51. Using statistical regression test the values of equation constant and regression coefficient were measured and tabulated in Table 4.52. Simulating standard formula-1, equation-10 was established. It can be used to estimate fabric weight per square meter by knowing the yarn count. The equation -7 is valid for yarn counts from 24/1 to 36/1. 푌 = 퐴 + 퐵 × 푋 ------1 Weight = 296.04 – 5.21× Ne------10

Table 4.52: Regression test for fabric weight against yarn counts Ne 36 , 30and 24 variable formula Rsq d.f F Sigf A B weight linear 0.992 34 4128.17 0.000 292.944 -5. 2139 Whereas Rsq=R square, df=degree of freedom, Sig =significant level A& B are equation constant

- 103 - 4.2.3.1.4 Fabric Extensibility:

Following Table 4.53 shows the results of fabric extension and recovery for barakat cotton yarn counts Ne 36, 30 and 24. From the t the average values of extension are 248.8, 229.2 and 185.3 corresponding to yarn counts Ne 36, 30 and 24 respectively. It is clear that the values of extension increased with increasing in yarn counts Ne. The greater extension that observed in fabric made from finer yarn count was mainly due to greater space around wales. The values of recovery are 183.8, 149.8 and 103 for the three counts Ne respectively. It is clear that the values of recovery increased with increasing in yarn counts Ne i.e. finer Ne.

Table 4.53: Results of fabric extension for different yarn counts Ne: 36, 30, and 24 property Extension % Recovery % Serial meter Ne 36 30 24 36 30 24 1 261.0 232.0 197.0 175.0 115.0 85.0 2 261.0 230.0 197.0 170.0 115.0 61.0 3 245.0 225.0 186.0 170.0 170.0 95.0 4 244.0 212.0 193.0 173.0 112.0 95.0 5 256.0 231.0 195.0 178.0 120.0 74.0 6 255.0 235.0 200.0 188.0 110.0 85.0 7 245.0 225.0 170.0 194.0 175.0 130.0 8 247.0 230.0 172.0 190.0 175.0 120.0 9 242.0 235.0 175.0 192.0 175.0 125.0 10 240.0 230.0 180.0 192.0 176.0 125.0 11 245.0 230.0 178.0 193.0 175.0 115.0 12 245.0 235.0 180.0 190.0 180.0 130.0 Ave. 248.8 229.2 185.3 183.8 149.8 103.3

The results are graphically shown in Figure 4.26. The graph shows straight line reflects the increasing values of extension against yarn counts Ne, as shown in the left figure. The right figure reflects the relation between yarn counts Ne and fabric recovery, it is linear similar to extension.

- 104 -

180 280

160 260

240 140

220 recovry % 120

extinsion %

200 100

180 80 24 30 36 24 30 36

y arn count Ne y arn count Ne

Figure 4.26: Effect of yarn count Ne on fabric extension and recovery %

High positive correlation coefficient approximately (0.9) was found between fabric extension values and yarn counts Ne, as shown in Table 4.54. High positive correlation value approximately 0.8 is observed for the fabric recovery.

Table 4.54: Correlation test for fabric extension and recovery against yarn count count Ne extension recovery count Ne Pearson Correlation 1 0.935** 0.823** Sig. (2-tailed) . 0.000 0.000 ** Correlation is significant at the 0.01 level (2-tailed).

By using statistical regression test, the values of equation constant and regression coefficients were found as shown in Table 4.55, For both extension and recovery values.

Table 4.55: Regression test for fabric extension against yarn count Ne variable formula Rsq d.f F Sigf A B Extension % linear 0.874 34 236.47 0.000 62.125 5.2986 Recovery % linear 0.678 34 71.50 0.000 -55.403 6.7014 Whereas Rsq=R square, df=degree of freedom, Sig =significant level, A& B are equation constant

- 105 - Simulating standard formula-1, equation-11 was established. It can be used to estimate extension parentage by knowing yarn count Ne. equation-11 is true for yarn counts from Ne 36 to Ne 24. Equation-9 is true for yarn counts Ne 36 and Ne 24 only. 푌 = 퐴 + 퐵 × 푋 ------1 Extension = 62.13 + 5.3 × Ne------11

Recovery = 6.7×Ne – 55.4 ------12

- 106 - 4.2.4 Investigation of effect of yarn waxing in knitting performance: 4.2.4.1Tension build-up during operation of knitting machine by using waxed and un-waxed yarn: The measurement of tension levels build-up during knitting machine operations at different elements by using waxed and un-waxed barakat yarn Ne 20 are shown in Table 4.56, for all feeders. From the table it is observed that the tension values obtained by using waxed yarn at packages zones are equal to zero. This is the starting point of the yarn passages upwards to the upper tension devices. When the yarn passed downwards to the feeders it was rubbed with different machine elements, then the tension increased from zero at packages zone to 2.3 at feeders zone and up to 5.4cN at knitting zone.

Table 4.56: Tension build-up by using waxed and un-waxed barakat cotton yarn Ne 20 At different zones in knitting machine Yarn type Waxed Un-waxed Packages z package feeder knitting package feeder knitting 1 0.0 2.0 6.0 0.0 2.3 7.0 2 0.0 2.0 6.0 0.0 3.0 7.0 3 0.0 3.2 4.5 0.0 3.2 4.5 4 0.0 3.2 5.5 0.0 3.2 4.5 5 0.0 1.2 6.0 0.0 1.5 5.5 6 0.0 2.0 6.5 0.0 2.0 5.5 7 0.0 2.0 5.0 0.0 2.0 5.0 8 0.0 2.5 4.5 0.0 2.5 7.0 9 0.0 2.5 4.5 0.0 2.3 4.5 10 0.0 2.5 3.5 0.0 2.5 3.5 11 0.0 2.0 5.5 0.0 2.0 5.0 12 0.0 2.0 5.0 0.0 2.0 5.5 13 0.0 3.5 5.5 0.0 2.8 5.5 14 0.0 2.0 6.5 0.0 3.0 7.5 15 0.0 1.2 5.5 0.0 2.0 6.0 16 0.0 2.0 6.0 0.0 2.2 7.5 Ave. 0.0 2. 3 5.4 0.0 2.4 5.7 Whereas: z = different zones in the machine

From the Table 4.56 it is observed that the tension values at package zones are equal to zero. This is the starting point of the yarn passages upwards to the upper tension devices,

- 107 - similar to result obtained by using waxed yarns. The tension increased from zero at packages zone to 2.4 cN at feeders zone and up to 5.7 cN at knitting zone. The tension remained within the required limits. The average results of tension levels build-up during knitting machine operation by using waxed and un-waxed yarn Ne 20 are shown in Table 4.57. Small differences in tension values are observed for the two yarns waxed and un-waxed. The results are illustrated in Figure 4.27, the two plots are similar.

Table 4.57: Ave. tension cN build-up by using waxed and un-waxed cotton yarn Ne 20 Property Machine Packages Feeders Knitting lement Tension cN by Waxed barakat cotton 0.0 2. 3 5.4 Tension cN by un-waxed barakat cotton 0.0 2.4 5.7

8

7

6

5

4

tension in cN 3 y arn ty pe: 2 1 waxed y arn 1

0 2 un-waxed package feeder knitting

zoon in machine

Figure 4.27: Average tension levels in cN for waxed and un-waxed cotton yarn

By applying statistical pair test the result of tension build up by using waxed and un-waxed cotton yarns aren’t significant as p = 0.114 and > 0.05. as shown Table 4.58

- 108 - Table 4.58: Pair test for tension build-up by waxed and un-waxed yarn Paired Difference 95% Confidence t df Sig. Interval (2taild) Lower Upper Pair waxed – un-waxed yarn -0.3231 0.0356 -1.612 47 0.114

4.2.4.2 Fabric abrasions by using waxed and un-waxed yarns: Table 4.59 shows the results of measuring weights of fabric sample in grams per square meter for abraded waxed and un-waxed knitted fabrics. It is clear from the table that, for waxed and un-waxed fabrics, the weight of fabric was decreased with increasing of the abrasion cycles. Also from the table the first abrading cycle (100) did not affect the fabric made from waxed yarn, as the fabric weight 191.7 remain constant and started abrading after the second cycle ( 200 ) due to the effect of waxing. Table 4.59: Gm/sqm of abraded fabrics by waxed and un-waxed cotton yarn Ne 20/1 Un-waxed waxed type No C start 100 200 300 400 1000 start 100 200 300 400 1000 1 193.0 192.8 192.6 192.5 192.4 191.1 192.7 192.6 192.5 192.4 192.0 190.4 2 189.7 189.6 189.4 189.4 189.0 188.0 187.6 187.6 187.2 187.1 186.9 185.7 3 192.7 192.4 192.1 191.8 191.4 191.4 193.3 193.3 193.2 193.0 192.8 191.5 4 189.5 189.2 188.8 188.5 188.4 187.4 193.3 193.3 193.0 192.8 192.5 191.7 Ave. 191.2 191.0 190.7 190.6 190.3 189.5 191.7 191.7 191.5 191.3 191.1 189.8 Where No = number of test C= abrasion cycles start = original weight in gm

The abraded weights i.e. lost weights from the fabric by abrasion were calculated and tabulated in Table 4.60. It is observed from the table that the lost weights vary from cycle to cycle but the first 100 cycle do not affect the fabric made from waxed yarns.

Table 4.60: Abraded weights gms for fabric made from waxed and un-waxed yarn Gm Abraded weight C y Waxed Un-waxed 100 0.0 0.2 200 0.2 0.3 300 0.2 0.2 400 0.3 0.3 1000 1.2 0.8 Where C= abrasion cycles, y = yarn type

- 109 - Figure 4.28 shows the relation between abrading cycles and weights lost by abrasion of fabrics samples made from un-waxed and waxed cotton yarns respectively. The two curves are approximately similar.

1.4

1.2

1.0

.8

.6

Abraded weight gm .4 Yarn type:

.2 w axed yarn

0.0 un-w axed yarn 100 200 300 400 1000

Abrasion cycles

Figure 4.28: Weight of abraded knitted fabrics against abrading cycles

The difference between weights lost from fabrics made from waxed and un-waxed yarns is not significant as p = 0.561 and > 0.05, the confidence intervals equal 0.3 and 0.5 not include zero as shown in Table 4.61.

Table 4.61: Pair tests for abraded waxed un-waxed knitted fabrics 95% Confidence Paired Differences interval t df Sig. (2tailed) Lower Upper Pair waxed - un-waxed fabrics -0.339 0.539 0.632 4 0.561

- 110 - 4.2.5 Investigation of knitting machine speed on knitting performance: 4.2.5.1 Result of measurement of tension levels at knitting zone: Table 4.62 gives the measured tension levels, on yarns, at knitting machine zone. From the table the average results of tension level remained constant for very low and low speeds, and increased from medium to high speeds. The result were illustrated graphically in Figure 4.29. Table 4.62: Measurement of tension (cN) (1.02gm) at knitting zone for various operating speeds cN Tension Sr Feeders very low low medium High 1 5 5 5 5 2 5 5 5 5 3 5 5 5 5 4 5 5 5 5 5 5 5 5 5 6 5 5 5 5 7 5 5 7 10 8 5 5 5 5 9 5 5 5 5 10 5 5 5 5 11 5 5 5 5 12 5 5 5 5 13 5 5 5 5 14 5 5 5 5 15 5 5 5 5 16 5 5 5 15 Av. 5 5 5.1 6 Were Sr = knitting speed range

- 111 - 6.2

6.0

5.8

5.6

5.4

5.2

Mean in tension cN 5.0 4.8 very low low medium high

speed range Figure 4.29: Tension build-up during increasing knitting machine speed

The relation between increasing knitting machine speed and tensions cN is not significant as p = .176 and > .05 even the correlation coefficient is high as shown in Table 4.63. Table 4.63: Correlation test for tension cN at knitting zone by increasing operating speeds speed range tension in cN Pearson Correlation 0.824 Sig. (2-tailed) 0.176 * Correlation is significant at the 0.05 level (2-tailed). 4.2.5.2 Rate of breakage with increasing speed: Table 4.64 shows the average values of rate of breakage per hour as with increasing knitting machine speed. From the table, no relation was observed between increasing machine speeds and rate of breakages per hour.

Table 4.64: Average results of yarn breakages per hour for various operating speeds speed v.low low medium high range Property breakage\hr 3 1 1 2

On the base of significant statistical values in section 3.3.2.1 and from Table 4.65, the statistical correlation tests showed weak relationship ≈ 0.41. It is not significant, as p = 0.6 and > 0.05. Table 4.65: Correlation test for rate of breakage against increasing machine speeds rate of breakage speed ranges rate of breakage Pearson Correlation 1 -0.405 Sig. (2-tailed) . 0.595

- 112 - Chapter Five:

Conclusion and Recommendations

- 113 - 5.1 Conclusion:

1. A significant poorness, of manual setting of tension levels and stitch length, was observed. 2. Clear differences on knitted fabrics produced by the initial and readjusted settings were observed. 3. Improving fabric quality was obtained by readjusting machine setting 4. Accordingly, this study reflects poorness of manual setting of the knitter against the adjusting of tension levels and loop lengths. 5. Mathematical relationships were established for quick response: loop length, yarn count versus fabric specification 6. Greater tension was build-up, during operation, by using un-waxed yarns at package & knitting zones not significant 7. A slight increase in tension was found at high speeds, not significant 8. High rate of breakages was found for extra high and very low speed ranges, no significant relation was found. 9. All visited factories did not possess measuring instruments for measuring yarn tension. 10. Manual control of tension causes variation within feeders. 11. The measuring device for determining yarn tension helped in improving fabric quality 12. Information about local industry was established 13. The investigation of waxed and un-waxed yarns resulted with greater tension was build-up, during operation, by using un-waxed yarns at package & knitting zones, but statistically not significant. The difference of the effect of abrading on waxed and un- waxed knitted fabrics was small and not significant. 14. The investigation of the increasing knitting machine speeds: very low, low, medium, and high on tension build-up during operation at knitting zones. It showed slight change on tension (5 cN) for high operating speed but within the scientific tolerance. High rate of breakages was found for extra high and very low speed ranges. Statistical results show no significant relation.

- 114 - 5.2 Recommendations:

Based in this study the following points are recommended: • Investigation to the plant layout and machinery arrangement, since only 41.7 % from the visited factories provided good aisle. • Possibility of manufacturing technical products for example, medical belts .Which were not observed during the survey. • More investigation is required to the effect of yarn waxing on local knitting performance.

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