THE OPTIMIZATION OF OPEN END SPINNING WITH RESPECT TO ENERGY CONSUMPTION
A THESIS Presented to The Faculty of the Division of Graduate Studies By Stuart Syen
In Partial Fulfillment of the Requirements for the Degree Master of Science in Textiles
Georgia Institute of Technology October, 1976 THE OPTIMIZATION OF OPEN END SPINNING WITH
RESPECT TO ENERGY CONSUMPTION
Appcovedi.
David IT Brookstein, Chairman / : ^ ,.David^>R. Gentry SJ
~Ml Dejm^y^'i^ston^ J^
Date Approved by Chairman y (PC^Z/fc? 11
ACKNOWLEDGMENTS
I would like to express my deepest appreciation to my thesis advisor and friend, Dr. David S. Brookstein, whose guidance and encouragement made this thesis possible. Special thanks also should go to Dr. David R. Gentry for his advice during the early part of my studies at Georgia Tech and for serving on my reading committee.
Dr. Milos Konopasek rendered invaluable assistance with the computer work for which I am especially grateful. Special mention should go to Mr. Mat Sikorski for his help in connecting the power measuring equipment, Mr. Fay Smith for keeping the spinning frame running, and Mr. Jim Maxwell of Coats and Clark for supplying the necessary sliver and performing evenness tests on the yarn. Ill
TABLE OF CONTENTS
Page ACKNOWLEDGMENTS ii LIST OF TABLES v LIST OF ILLUSTRATIONS vii SUMMARY ix Chapter I. INTRODUCTION 1 1.1. Statement of the Problem 1.2. Review of Literature I.2.a. Energy Consumption in Open End Spinning I.2.b. Effect of Combing Roller Speed on Open End Spun Yarn I.2.C. Effect of Combing Roller Wire Design on Open End Spun Yarn I.2.d. Effect of Twist and Rotor Speed on Open End Yarn II. EXPERIMENTAL PROCEDURE AND INVESTIGATIONS .... 14 11.1. Scope of Experimental Investigation 11.2. Equipment for Experimental Investigation 11.2.a. Laboratory Open End Spinning Frame II.2.b. Energy Measuring Equipment 11.2.c. Sliver II.2.d. Testing Equipment 11.3. Experimental Procedure II.3.a. Spinning at Different Test Conditions II.3.b. Measuring Energy Consumption II.3.c. Testing the Yarn III. RESULTS AND DISCUSSION 20 III.l. Comparison of Laboratory Open End Spun Yarn with Mill Open End Spun Yarn IV
Chapter Page 111.2. Yarn Strength III.2.a. The Effect of Combing Roller Speed on Yarn Strength III.2.b. The Effect of Twist Multiple on Yarn Strength III.2.C, The Effect of Yarn Linear Density on Tenacity 111.3. Yarn Elongation III.3.a. The Effect of Combing Roller Speed on Yarn Elongation III.3.b. The Effect of Twist Multiple on Yarn Elongation 111. 4. Yarn Energy to Break III.4.a. The Effect of Combing Roller Speed on Yarn Energy to Break III.4.b. The Effect of Twist Multiple on Yarn Energy to Break III. 5. Yarn Uniformity III.5.a. The Effect of Combing Roller Speed on Yarn Uniformity Ill.S.b. The Effect of Twist Multiple on Yarn Uniformity III.5.C. Yarn Evenness and Strength III.6. Optimization of Open End Yarn Properties with Respect to Energy Consumption IV. CONCLUSIONS 56 V. RECOMMENDATIONS 5 8 Appendix A. YARN TEST RESULTS 59 B. ENERGY CONSUMPTION MEASUREMENTS 68 C. QAS PROGRAM 70 D. ISO-GRAPHS FOR ENERGY CONSUMPTION AND YARN PROPERTIES 72 BIBLIOGRAPHY 84 LIST OF TABLES
Table Page 1. Breakdown of Energy Costs in Ring Spinning. ... 7 2. Breakdown of Energy Costs in Open End Spinning. . 8 3. Investigated Parameters and the Number of Test Conditions Used to Investigate the Effect of the Four Parameters 14 4. Sliver Specifications 16
5. Strength and Uniformity of Mill and Laboratory Yarn 2 0 6. The General Model for Energy Consumption and Yarn Properties 42 7. Model of Energy Consumption and Yarn Properties for 42 Tex Cotton 43 8. The Optimization Problem for 42 Tex Cotton. ... 44 9. Yarn Tensile Strength for 32 Tex Cotton 60 10. Percent Elongation for 32 Tex Cotton 60 11. Energy to Break for 32 Tex Cotton 61 12. %CV for 32 Tex Cotton 61 13. Yarn Tensile Strength for 42 Tex Cotton 62 14. Percent Elongation for 42 Tex Cotton 62 15. Energy to Break for 42 Tex Cotton 63 16. ICV for 42 Tex Cotton 63 17. Yarn Tensile Strength for 32 Tex Cotton/Polyester 64 18. Percent Elongation for 32 Tex Cotton/Polyester. . 64 19. Energy to Break for 32 Tex Cotton/Polyester ... 65 VI
Table Page 20. %CY for 32 Tex Cotton/Polyester 65 21. Yarn Tensile Strength for 42 Tex Cotton/Polyester. 66 22. Percent Elongation for 42 Tex Cotton/Polyester . . 66 23. Energy to Break for 42 Tex Cotton/Polyester. ... 67 24. %CV for 42 Tex Cotton/Polyester 67 25. Energy Consumption for Open End Spinning 69 Vll
LIST OF ILLUSTRATIONS
Figure Page 1. Open End Spinning Head 3 2. Power Input for Spinning Operations Using Ring Frames 9 3. Power Input for Spinning Operations Using Open End Frames 9 4. Effect of Combing Roller on Yarn Strength .... 22 5. Effect of Twist Multiple on Yarn Strength .... 25 6. Structure of Ring and Open End Spun Yarn 2 7 7. Effect of Combing Roller Speed on Yarn Elongation 30
8. Effect of Twist Multiple on Yarn Elongation ... 32
9. Effect of Combing Roller Speed on Yarn Energy to Break 34 10. Effect of Twist Multiple on Yarn Energy to Break. 36
11. Effect of Combing Roller Speed on Yarn Uniformity 37
12. Effect of Twist Multiple on Yarn Uniformity ... 39 13. Strength-Energy Iso-Curves for 42 Tex Cotton. . . 46 14. Elongation-Energy Iso-Curves for 42 Tex Cotton. . 47 15. Energy to Break-Energy Iso-Curves for 42 Tex Cotton , 48 16. Uniformity-Energy Iso-Curves for 42 Tex Cotton. . 49
17. Solution Space for 42 Tex Cotton 50 18. Flowchart for Minimizing Energy Consumption Considering Strength, Elongation, Energy to Break and Energy Consumption 52 Vlll
Figure Page 19. Minimization of Energy Consumption with Respect to Strength Elongation and Energy to Break. ... 53 20. Minimization of Energy Consumption with Respect to Uniformity 55 21. Strength-Energy Iso-Curves for 42 Tex Cotton/ Polyester 73 22. Elongation-Energy Iso-Curves for 42 Tex Cotton Polyester 74 23. Energy to Break-Energy Iso-Curves for 42 Tex Cotton/Polyester 75 24. Uniformity-Energy Iso-Curves for 42 Tex Cotton/Polyester 76
25. Strength-Energy Iso-Curves for 32 Tex Cotton. . . 77
26. Elongation-Energy Iso Curves for 32 Tex Cotton. . 78
27. Energy to Break-Energy Iso-Curves for 32 Tex Cotton 79 28. Uniformity-Energy Iso-Curves for 32 Tex Cotton. . 80
29. Strength-Energy Iso-Curves for 32 Tex Cotton/ Polyester 81 30. Elongation-Energy Iso-Curves for 32 Tex Cotton/ Polyester 82 31. Energy to Break Energy Iso-Curves for 32 Tex Cotton/Polyester 83 IX
SUMMARY
This research is concerned with optimizing energy consumption during open end spinning without adversely affecting yarn quality or rate of production. The method of optimization consists of testing yarn, spun at levels of rotor and combing roller speeds, to determine the effect of machine parameters on yarn properties.
It can be concluded that a given level of strength, elongation, energy to break or uniformity can be achieved at different combinations of combing roller and rotor speed. Since lower speeds result in lower energy consumption, the properties of open end spun yarn can be optimized with respect to energy consumption by finding the lowest combing roller and rotor speed combination that produce acceptable strength, elongation, energy to break and uniformity. CHAPTER I
INTRODUCTION
I.l. Statement of the Problem Until the early 1970's, the United States was fortunate to have relatively abundant and inexpensive energy. As a result, technological advances in the textile industry had been aimed toward increasing the utilization of labor and capital. Accordingly, power consumption was of no major concern, for it was less expensive per unit of production than capital or labor; however, energy is now more expensive. Current trends indicate that it will become even more expensive and the possibility for power interruption will exist. The textile industry is a labor intensive industry. In attempting to reduce the cost of labor per unit production of goods, technical developments in the textile industry have been focused towards increasing output per man and machine-hour and these developments have led to increased speeds for existing processes as well as the development of new technologies. Open end spinning was developed with a view toward increasing the productivity of the yarn spinning process beyond the limiting speeds of ring spinning. The process was developed at a time when fuels used to produce electrical energy were relatively abundant and inexpensive. At the time of development, the increased productivity per man and machine-hour justified the increased rate of energy consump tion; however, today the cost of electrical energy has risen dramatically and it remains to reevaluate manufacturing processes to determine if they can be run at reduced levels of power consumption without significantly impairing the quality of finished goods. Until recently, energy consumption has not received serious attention from the designers of open end spinning systems. An examination of a laboratory open end spinning frame suggests that a study of the material-machine inter actions occurring at those stations in the spinning system that are primary users of energy but whose contributions to the process do not affect the rate of productivity may lead to recommendations that would serve to reduce the speeds of these components and accordingly system energy consumption. Open end spinning systems consist primarily of six sequential operations (Figure 1). They are the following: 1. Fiber Separation--the continuity of fiber flow is broken by separating tufts of fibers from the feed sliver at the combing roller. 2. Fiber Transport--the fibers flow in an air channel from the combing station to the spinning chamber. 3. Fiber Condensation on the Spinning Surface-- 3. FIBER CONDENSATION 4. REMOVAL OF FIBER ASSEMBLY ON THE SPINNING SURFACE FROM COLLECTING SURFACE ' 3 5. TWIST INSERTION 6^INDING
2. FIBER TRANSPORT
1. FIBE:R SEPARATION
Figure 1. Open End Spinning Head centrifugal forces cause fibers to move from their central entry point at the rotor to the groove on the circumference of the rotor. 4. The Removal of the Fiber Assembly from the Collecting Surface--fibers are pulled off the collecting surface and out of the rotor by the tail of the preceding formed yarn. 5. Twist Insertion--the revolving spinning chamber, twisting the tail of the yarn while it is restrained at the take up roll, results in real twist. 6. Winding--for open end spinning, winding is a separate process taking place after the yarn is removed from the spinning chamber. Energy is likely to be consumed mostly during fiber separation, twist insertion, and winding. Changes in the speeds of these operations alter the energy consumption of the open end frame; however, they do not necessarily change the productivity. For example, altering the degree of fiber separation or the amount of twist at a given winding speed does not affect the output of the unit; changing the winding speed directly affects output. Accordingly, energy economies may be achieved by changing the speed of those operations which are primary users of energy but do not affect the unit rate of output of the process. No economy can be achieved by reducing the speed of the winding roller because the energy reduction is accompanied by a reduction in unit rate o£ output. Hence, optimization o£ the open end spinning process with respect to power consumption, requires determi nation of the effects of the degrees of both fiber separation and fiber twisting on system power consumption and yarn quality. The objectives of this study are: 1. To determine the effects of modifying the amount of fiber separation and twist on yarn strength, elongation, energy to break, uniformity and energy consumption per gram of yarn produced. 2. To develop an empirical model which can be used to predict the above parameters. 3. To develop a methodology for determining the minimum energy consumption, per gram of yarn, required to produce a yarn of given strength, elongation, energy to break or uniformity. Summarizing, this study indicates how energy consump tion can be reduced by reducing the speeds of the combing roller and rotor. These are significant in view of the fact that spinning consumes more energy per gram of yarn produced than any other process in yarn manufacturing.
1.2. Review of Literature I.2.a. Energy Consumption In Open End Spinning Spinning represents approximately 68 percent of yarn manufacturing costs. Over 60 percent of the power required in yarn manufacturing is consumed during spinning and 75 percent of this is consumed by spinning machinery. The remaining 25 percent is consumed by lighting and air condi tioning. Therefore, a reduction in power consumption during spinning would yield significant savings in yarn manufacturing costs (Tables 1 and 2; Figures 2 and 3). Previous studies of energy consumption for open end spinning only consider the rotor as a variable. The following empirical relationship for energy consumption of the rotor
IS reported:
Pw a(^N s ^•^-)^ (^R s ^'^)^
P = power consumption N = speed of rotation
Rs = chamber radius An example of the difference in power consumption at two specific rotor speeds is shown:
Pw 2^ = 2.57 Pw Tl
P ^ = power consumption at 45,000 rpm P ^ = power consumption at 30,000 rpm The above relationship clearly shows that the power require ments are more than double for a 50 percent increase in rotor speed. Table 1. Breakdown of Energy Cost in Ring Spinning Energy price: 0.13 sFr/kWh Cost Headings Breakdown of energy costs
sFr/kg °^ sFr/kg
1 Energy 0.193 11.6 1 Opening RooinO.025 13.1 2 Wages 0.463 27.8 2 Carding 0.029 15.0 3 Waste 0.297 17.8 3 Drawframes 0.011 5.9 4 Operating 0.054 3.3 4 Roving 0.013 7.0 materials frames 5 Capital 0.658 39.5 5 Ring frames 0.114 59.0 Total 1.665 100.0 Total 0.192 100.0 Table 2. Breakdown of Energy Cost in Open End Spinning
Energy price: 0.13 sFr/kWh Cost headings Breakdown of energy costs 1
sFr/kg % sFr/kg
1 Energy 0.2279 14.2 1 Opening 0.0254 11.1 room 2 Wages 0.2427 15.1 2 Carding 0.0293 12.9 3 Waste 0.2846 17.7 3 DrawframesO.0167 7.3 4 Operating 0.1031 6.4 4 OE Spinner0.1565 68.7 materials 5 Capital 0.7492 46.6 Total 1.6075 100.0 Total 0.2279 100.0 1 Air Conditioning 52 kW 2 Lighting 23 kW 3 Machinery 260 kW Total 3ir TW Figure 2. Power Input for Spinning Operators Using Ring Frames^
1 Air Conditioning 66 kW 2 Lighting 22 kW 3 Machinery 3 06 kW Total 394 kW
Figure 3. Power Input for Spinning Operations Using Open End Frames^ 10
I.2.b. Effect of the Combing Roller Speed on Open End Spun Yarn An important parameter in open end spinning is the combing roller speed. Empirical data indicates that as the rate of combing is increased, a greater separation force is 3 exerted on the fibers. This reduces entanglement of fibers in the rotor producing a yarn with less thick places, thin places and other defects. However, increased separation force damages a great percentage of fibers causing reduced 3 yarn strength. Combing roller speed also affects the stability of the open end system, and reducing combing roller speed results in more end breaks during spinning. Yarn tenacity, irregularity and the number of imperfec tions are affected by both the combing roller speed and the type of sliver; therefore strength, tenacity, irregularity and the number of imperfections can be used to measure the effectiveness of combing. Increasing combing roller speeds reduces the number of imperfections with only slight reduc- tions in the yarn strength of 100 percent cotton. 4 A strong correlation between combing roller speed and yarn strength is not found in 100 percent cotton; however, a positive correlation is found between strength and combing roller 3 speed for rayon. I.2.C. The Effect of Combing Roller Wire Design Two parameters of the combing roller design can be varied by the manufacturer. They are the wire angle and the 11
number of wires per inch. As the wire angle is increased, the rate of combing is reduced. As the number of wires per 3 inch is increased, the rate of combing is increased. An increase in the combing rate caused by combing roller design, 3 decreases yarn tenacity and improves uniformity. It is recognized that the combing roller design has a significant effect on yarn properties; however, this research is only concerned with combing roller speed because energy consumption is directly related to speed. I.2.d. Effect of Twist and Rotor Speed on Open End Yarn The effect of increasing the rotor speed can be divided into contributing forces. One force is the effect of the increased twist caused by increased rotor speed. The second force is the effect of changes in the static pressure within the rotor. Increasing the twist, improves yarn strength, elongation and energy to break. As twist increases, the helix angle of the fibers increase resulting in a subsequent impairment of fiber contribution to yarn strength. When the fiber contribution to yarn strength, elonga tion and energy to break is impaired to the point where the increased contact between the fibers no longer contributes enough to balance this impairment, a loss in yarn physical properties results. The effect of changes in static pressure are not clearly understood; however, there is an optimum static pressure for each fiber and deviations from it result 12
in losses in all yarn physical properties. The twist versus yarn-tenacity relationship for open end spun yarn is similar to that of ring spun yarn. However, open end yarns with the same nominal twist multiple as ring 4 spun yarns are generally 10-30 percent weaker. Real twist is unknown for open end yarns because the twist efficiency, the amount of machine twist translated into actual yarn twist, changes with variations in fiber, sliver linear 2 density, feed rate and rotor speed. Twist efficiency decreases with increases in machine twist because increasing the machine twist increases the number of doublings in the rotor and results in a greater amount of fibers in the yarn cross section and an increased reaction to the turning moment 2 of the fibers. The turning moment is different for each type of fiber; therefore, the twist efficiency will also 2 change for each fiber or blend. Losses in twist due to 2 efficiency are on the order of 10-30 percent.
Previous studies indicate that increased rotor speeds result in poorer cotton yarn physical properties. This is attributed to an alteration of the static pressure within the rotor. For example, cotton has the lowest tenacity, the largest number of imperfections and the highest short term irregularity at highest rotor speeds. Decreased opening is one possible explanation for this decrease in yarn properties. Decreased opening occurs because the higher feed rates that are used with higher rotor speeds 13
result in a decreased amount of combing roller wire points per fiber. As the number of wire points per fiber are reduced, fiber separation is reduced and less opening occurs. Increas ing the combing roller speed could increase opening to the desired level; however, it would also increase fiber breakage. Therefore, since the combing roller speed cannot be increased to balance out the opening lost at higher feed rates, there is a higher frequency of thick, thin and weak spots which result in a higher ends down rate during spinning. Higher end breakage rates are compounded by the fact that piecing up is more difficult at higher rotor speeds. 14
CHAPTER II
EXPERIMENTAL PROCEDURE AND INVESTIGATION
II.1. Scope of Experimental Investigation A total of four parameters involving 48 different test conditions were examined to determine the effect of the material-machine interactions on yarn tensile strength, elongation, energy to break and irregularity. Energy consump tion was evaluated by measuring the power used during each test condition. Table 3 lists the parameters studied and Appendix A lists all experiments with the corresponding results.
Table 3. Investigated Parameters and the Number of Test Conditions Used to Investigate the Effect of the Four Parameters
Parameter Description No. of Conditions No. ^ 1 Effect of combing roller speed 3-5 2 Effect of twist multiple 3 3 Effect of fiber type 2 4 Effect of linear density 2 15
II.2. Equipment for Experimental Investigation II.2.a. Laboratory Open End Spinning Frame A laboratory open end spinning machine with standard Toyoda BD-200 spinning heads, built at Georgia Tech, was used for spinning all of the yarns for this investigation. This machine is designed so that one can independently alter the combing roller speed, rotor speed and take up roller speed. The combing roller drive is fitted with a variable speed motor and controller. The rotor and take-up drives are belt and gear driven with constant speed motors. Accord ingly, the rotor and take up roller speeds can be altered by changing gears or pulleys. This device is unique in that combing roller speeds can be altered quickly and without affecting the operation of the other components of the process . II.2.b. Energy Measuring Equipment The energy consumption of the laboratory open end spinning frame used for this research is measured by metering the amount of power drawn by the two lines which supply electricity to the open end spinning frame. Since these two lines do not deliver the same voltage, they have to be measured separately. The 110 volt line which supplies power to the combing roller was metered with an indicating wattmeter The 220 volt line which supplies power to the rotor and take up drives is also metered with an indicating wattmeter; however, a shunt transformer was placed between this line and 16
the meter to reduce the current through the meter. This enabled measurement o£ the power without overloading the meter. A safety switch was also employed to divert current around the meters when power measurements are not needed. II.2 .c. Sliver Yarn was spun from the three slivers whose properties are listed in Table 4. The 52 grain sliver obtained from the Russell Corporation was used to determine if the laboratory open end spinning frame was producing yarn of comparable quality to that from a standard production machine. The Russell Corporation currently spins yarn from it on a commercial BD-200 spinning frame. Hence, the measured properties of the yarn spun from this sliver on the laboratory open end spinning frame can be compared with those same properties of the yarn spun on conventional equipment. The remaining two slivers, obtained from Coats and Clark Incorporated, were used for the remaining tests.
Table 4. Sliver Specifications
Linear Density Staple Length Fiber Supplied by
52 grain 1-1/16 inch cotton Russell Corporation 65 grain 1-1/16 inch cotton Coats and Clark 65 grain 1-1/16 inch/ 65% polyester/ Coats and Clark 1-1/2 inch 35% cotton 17
II.2.d. Testing Equipment A Uster constant rate of load single end strength tester was used to obtain comparison results with the Russell Corporation for the 52 grain sliver. The Uster was employed because the Russell Corporation performs their yarn tests on it. Accurate comparisons can be made between the Georgia Tech laboratory open end spun yarn and that of the Russell Corporation since the sliver and the testing procedure are the same. Testing for the majority o£ the experimental work was accomplished on an Instron constant rate of extension tensile tester and a Uster evenness tester. Strength, elongation and energy to break were measured on the Instron. Evenness and the number of imperfections per unit length were measured on the Uster. Evenness was measured in U (Uster) percent and converted to %CV (coefficient of variation) by multi plying it by a factor of 1.25.
II.5. Experimental Procedure The objectives of the experimental program were to measure the strength, elongation, energy to break, uniformity and power consumption for each of the yarns produced under the 48 different test conditions. Physical yarn properties were then related to energy consumption. II.5.a. Spinning at Different Test Conditions To spin at a particular set of machine parameters, the feed roll speed was first set at the speed which provides the proper draft for the particular linear density of yarn to be spun. Once the adjustments for yarn linear density were made, the twist multiple was set by attaching the proper combination of pulleys which give the proper rotor speed for the amount of twist required. The real twist of open end spun yarn is not known for twisting is not 100 percent efficient. The twist is frequently stated as the ratio of rotor speed to take up speed. This is labeled machine or nominal twist. The real twist is lower than the machine twist because of twist slippage at the rotor surface. The rotor is in effect a friction twisting system and the torsional rigidity of the fibers inside it is great enough compared to the coefficient of friction between the fibers and the turbine wall to produce slippage; therefore, less than one turn of twist will be inserted for each rotor revolution. The loss of twist is on the order of 10-30 2 percent. The last parameter set was combing roller speed, This was individually controlled and the speed of the combing roller was set at 1000 rpm increments around Toyoda's recommended speed of 8000 rpm using a General Radio Strobo- j^ tach. The same combing roller is used throughout this research. At no time is the take up speed changed. This is kept constant to minimize changes in output. II.3.b. Measuring Energy Consumption The energy consumption for each test condition was 19
measured using a watt meter. The watt readings were then normalized to killowatt hours per killogram of yarn produced (Appendix B). II.5.c. Testing the Yarn Ten single end breaks for each yarn were made on the Instron to determine strength, elongation and energy to break. Each specimen was 6 inches in length. The jaw speed of the Instron was set at 2 inches per minute to give a breaking time of 20 ± 2 seconds as recommended in ASTM D-1682. A linear stress - strain relationship was used to determine energy to break since the majority of Instron test charts show a linear stress-strain response. The values of energy to break were calculated by taking one half of the load multipled by the elongation. It is then normalized to gram-centimeters per tex. Irregularity and imperfections per unit length were measured using a Uster evenness tester. Two five minute Uster tests, one at 8 yards per minute and the other at 100 yards per minute, were run at each experimental condition. The U% obtained was converted to %CV by multiplying it by a factor of 1.25. A spectrogram showing the amount of periodic defect was also obtained for each test. 20
CHAPTER III
RESULTS AND DISCUSSION
III.1. Comparison of Laboratory Open End Spun Yarn with Mill Open End Spun Yarn The strength and uniformity of yarn spun on a commer cial BD-200 open end spinning frame and of identical yarn spun on the laboratory unit used for this research are listed in Table 5. A justifiable comparison between the two yarns can be made because the sliver and the machine settings used to spin the laboratory yarn were the same as those used to spin the mill yarn. The sliver used to spin the laboratory yarn for this comparison was obtained from the same mill whose yarn it was compared to. This sliver was selected at random and received no special preparation.
Table 5. Strength and Uniformity of Mill and Laboratory Yarn Laboratory Commercial Yarn Yarn Breaking Load 300 gr 300-350 gr %CV 12% 15% Yarn specifications: 18 cc, TM 4.8, rotor speed 36000 rpm, combing roller speed 7000 rpm 21
Examination of the results in Table 5 reveals that the breaking load o£ the laboratory yarn is within the range of the commercial yarn and the ICV is lower for the same count of laboratory yarn. The results in Table 5 indicate that the laboratory open end spinning frame used for this research was producing yarn of commercial quality.
III. 2. Yarn Strength III.2.a. The Effect of the Combing Roller on Yarn Strength Figure 4 shows the effect of combing roller speed on yarn strength. In all cases, increases in combing roller speed resulted in a slight decrease in yarn strength. These reductions in yarn strength can be attributed to the increased fiber breakage associated with higher combing roller speeds. Although the differences in yarn strength with respect to combing roller speed were not found to be statistically significant in this research, previous studies have indicated slight decreases in strength as combing roller speed was increased. These slight decreases are shown by the best fit regression lines in Figure 4. The sensitivity of each yarn to increases in combing roller speed is represented by the steepness of their respective best fit regression lines. A steeper line indicates a greater degree of sensitivity than a relatively flat one. Figure 4 shows that the 32 and 42 tex cotton yarns are equally sensitive to changes in combing roller speed. Figure 4 also shows the 32 and 42 tex cotton/ 22
16
32 Tex Cotton/Polyester 14
12 42 Tex Cotton/Polyester X CD (D) -M
OD
X. -M OC
J-i TO >^ 42 Tex Cotton (o)
6 7 8 Combing Roller Speed (ooo)
Figure 4. Hffect of Combing Roller Speed on Yarn Strength 23
polyester yarn as having different sensitivity rates from each other as well as the two cotton yarns. Previous studies by Toyoda and Dyson have concluded that increased combing roller speed slightly reduces the strength of cotton yarn through increased fiber breakage. Dyson also studied the effects of combing roller speed on rayon and found significant reductions in yarn tenacity when the combing roller speed was increased. The study on rayon led Dyson to recommend a combing roller speed of 5340 rev/min to spin a 23 tex rayon yarn with a fiber length of 36.5 mm. This differs significantly from the Toyoda recommendation of using a combing roller speed of 8000 rev/min for cotton yarns. An interesting point introduced by Dyson is that the optimum combing roller speed for different fibers and linear densities may not be the same. This may be attributed to differences in interfiber friction resulting from increased surface contact or increased coefficients of friction between fibers. The interfiber friction acts as a force holding the fibers back into the sliver while the combing roller is exerting a force to pull it out. A longer fiber length will increase the area of contact which increases the total inter fiber friction. Different fibers may have different coeffi cients of friction between them which in turn changes the interfiber friction per unit area. It is well known that for opening to take place, the force exerted by the combing roller to pull fibers from the sliver must be greater than 24
the interfiber friction holding them back. The relative difference between combing force and interfiber friction determines the degree of opening that takes place; however, there is a limit to the total forces that can be put on a particular fiber. When the interfiber friction holding the fibers back is increased, the total stress on the fiber is increased and a higher combing force is required for the same opening to take place. The higher combing force, achieved by increasing the combing roller speed, increases the total stress on the fiber. A decrease in the wire angle or an increase in the wire point density on the combing roller would also increase the total stress on the fiber. ' As the forces exerted from both ends of the fiber approaches the fiber breaking stress, more fibers will be broken and yarn made from these fibers will be relatively weak. Ill.Z.b. The Effect of Twist Multiple on Yarn Strength The differences in cotton yarn strength with respect to twist multiple were statistically significant at the 95% confidence level while the differences in the cotton/ polyester yarn were not found statistically significant. However, the best fit regression lines in Figure 5 will be used in the ensuing discussions. In all but one case, yarn strength increases as twist multiple increases. For each yarn, the sensitivity of yarn strength to changes in twist multiple appears different for each yarn. As twist increases, the surface contact and the cohesive forces between the 2 5
16
32 Tex Cotton/Polyester 14
X (U 4-^ 12 OD 42 Tex Cotton Polyester - (a) x: c cu f- 10 otton (x) CO c
oj >- otton (o)
3.8 4.0 4.2 4.4 4.6 Twist Multiple
I'igurc 5. l',ffcct of Twist Multiple on Yarn Strength 26
fibers increase. This increase in cohesive forces contributes to increased yarn strength; however, there is a corresponding increase in the helix angles of the fibers which decreases the fiber contribution to yarn strength. Strength will increase when twist is increased if the increase in cohesion force is greater than the decrease in the component of the fiber strength. Previous studies by Toyoda and Dyson have found that the twist-tenacity relationships for open end spun yarn are similar to those of ring spun yarn except that the open end yarn is 10-30 percent weaker. This weakness can be attributed to the unique structure of open end spun yarns. Lord shows that O.E.S. yarns have characteristic "wrapper fibers which form a very steep helix angle with respect to the yarn axis as shown in Figure 6 and conse quently these fibers contribute little to the strength of o O.E.S. yarns. Increasing the twist is accomplished by increasing the rotor speed while the yarn throughout speed remains constant. Increasing the rotor speed also increases the static pressure within the rotor. Vaughn and Hiranprueck found that there is an interaction between static pressure and rotor speed which can cause variations in yarn strength. At rotor speeds approaching 60,000 rev/min small decreases in the physical properties of cotton yarn were noted. Dyson found no significant decrease in the strength of cotton yarn between 32,000 and 45,000 rev/min; however, there was 27
Ring Spun Structure
Wrapper Fibers
Open End Spun Structure
Figure 6. Structure of Ring and Open End Spun Yarns 28
a significant decrease in the strength of rayon yarn as the 2 rotor speed was increased from 26,000 to 36,000 rev/min. The differences in the variation of cotton and rayon yarn strength with changes in rotor speed indicate that fiber type plays an important part in bringing about this sensi tivity; therefore fiber type is an important parameter which effects how yarn strength to changes with rotor speed and should be considered when choosing a rotor speed. The reaction to the rotor speed of the 42 tex cotton/ polyester yarn may explain why this yarn lost strength when the twist multiple was increased. This yarn was spun with a rotor speed range at 26,000 to 36,000 rev/min where Dyson noted decreases in strength with increasing rotor speed. Another possible explanation for increasing rotor speed could be related to the fiber transport channel. During open end spinning, fibers are transported from the opening section to the spinning section through an air duct. The velocity of the air in this duct is determined by the speed of the rotor. Different fibers or blends of fibers may exhibit different and possibly nonuniform aerodynamic flow properties at different air flow velocities. If this happens, the fiber alignment in the spinning chamber may be» reduced resulting in decreased yarn strength. III.2.C. The Effect of Yarn Linear Density Tenacity Figures 4 and 5 show that low yarn linear densities have a greater tenacity at almost all the combing roller 29
speeds and twist multiples tested. These differences are statistically significant at the 95% confidence level. This may be attributed to the lower fiber feed rates used to make the smaller linear densities. The lower feed rate results in an increase in fiber opening because there are less fibers being fed in proportion to the number of teeth on the combing roller which in turn results in better fiber separa tion. Better fiber separation will cause increased alignment of the fibers in the spinning chamber which will result in better individual fiber contribution to yarn strength.
III.3. Yarn Elongation
III.3.a. The Effect of the Combing Roller Speed on Yarn
Elongation
Figure 7 shows the effect of combing roller speed on elongation. The differences in elongation were not found statistically significant in this research but a previous study conducted by Vaughn and Cox found them statistically 9 significant at a 95% confidence level. Because of the
Vaughn and Cox findings, the best fit regression lines obtained from data collected in this research will be used in the ensuing discussion as if they represented statistically significant differences. In all cases an increase in combing roller speed results in a decrease in yarn elongation. The elongation of both the 32 and 42 tex cotton yarns had rela tively less variation with changes in combing roller speed 30
16
42 Tex Cotton/Polyester (o) o ^ 14 irti Ofi 32 Tex Cotton/Polyester f^) C o 1—1 m
•*-> c <^ 12
L>
0) a,
10
-32 Tex Cotton W ^42 Tex Cotton (o)
6 7 8 Combing Roller Speed (ooo)
Figure 7. Effect of Combing Roller Speed on Yarn Elongation 31
than the cotton/polyester yarn. The sensitivities of both cotton yarns were about equal whereas the polyester yarn had different sensitivities at the two different linear densities. Fiber elongation, the amount of yarn twist, and length of fiber, help effect yarn elongation. Increasing combing roller speed subjects the fibers to greater forces resulting in more short fibers through increased breakage. Faster combing roller speeds, in effect, reduce the average fiber length. As the fiber length is reduced the fibers can move a small distance along the yarn axis before they completely slip past each other. The sensitivity of yarn elongation to combing roller speed depends on interfiber friction. The cotton/polyester yarn used in this research could not be spun at combing roller speeds below 7000 rev/min. Here, the spinning difficulty is a consequence of high inter fiber friction which exists because the polyester fiber is longer than the cotton fiber. As high interfiber friction is the case, there will be a greater force holding the fibers back and accordingly more force will be required by the combing roller to pull the fibers out and achieve adequate opening which results in higher fiber breakage. III.5.b. The Effect of Twist Multiple on Yarn Elongation
Figure 8 shows the effect of twist multiple on yarn elongation. Elongation for both the 42 tex cotton yarn and the 42 tex cotton/polyester yarn decreases as the twist multiple was increased while both 32 tex yarns had an increase 32
16
32 Tex Cotton/Polyester (A)
14 o "^ 42 Tex Cotton/Polyester •H -M (a)
DC
O T—I OJ 12 -M
CD O 5H 0) P-, 10
32 Tex Cotton (x)
42 Tex Cotton (o) o
3.8 4.0 4.2 4.4 4.6 Twist Multiple
Figure 8. Effect of Twist Multiple on Yarn Elongation 33
in elongation with increasing twist multiple. As the twist multiple \vas increased, two parameters which affect open end yarn are increased. The first parameter is the helix angle of the fibers and the second parameter is the rotor speed. The increased helix angle results in a lower compo nent of strain transferred to the fibers enabling the yarn to extend a greater distance before breaking than yarns with fibers aligned at lower helix angles. This explains the increase in elongation of the 32 tex yams when the twist was increased. The only explanation that can be offered for the decrease in elongation for the 42 tex yarns is that the increased rotor speed, which has been shown in previous studies to decrease elongation, had a greater effect on the change in elongation than the increase in the twist multiple and helix angles of the fibers on these heavier 42 tex yarns
III.4. Yarn Energy to Break III.4.a. The Effect of Combing Roller Speed on Yarn Energy to Break Figure 9 shows the effect of combing roller speed on energy to break. Energy to break is a function of both strength and elongation; therefore, the energy to break will be effected the same way as the yarns strength and elonga tion. Both the strength and elongation of the 32 tex cotton, 32 tex polyester/cotton and 42 tex cotton were reduced as combing roller speed was increased. It logically 34
32 Tex Cotton/Polyester
42 Tex Cotton/Polyester
X (D •M
Oj bO 32 Tex Cotton (x)
42 Tex Cotton (o)
(DJO ;M
6 7 8 9 Combing Roller Speed [ooo) Figure 9. Effect of Combing Roller Speed on Yarn Energy to Break 35 follows and is shown in Figure 9 that the energy to break for these three yarns should be reduced as the combing roller was increased. III.4.b. The Effect of Twist Multiple on Yarn Energy to Break Figure 10 shows the effect of twist multiple on energy to break. The 32 tex cotton, 32 tex cotton/polyester and 42 tex cotton had an increased energy to break as the twist multiple was increased. These results follow the increasing trends of strength and elongation for these three yarns as the twist multiple is increased. The 42 tex cotton/polyester had losses in both strength and elongation as the twist multiple was increased; therefore, it follows logically and is shown in Figure 10 that this yarn should require less energy to break at higher twist multiples. III. 5. Yarn Uniformity III.5.a. The Effect of Combing Roller Speed on Yarn Uniformity Figure 11 shows the effect of combing roller speed on yarn uniformity. In all the specimens tested, an increase in combing roller speed resulted in a decrease in %CV. This improved uniformity can be attributed to the increase in opening resulting from higher combing roller speeds. As the combing roller is speeded up, the teeth on it strike the fiber more times with more force resulting in better fiber separation 36 32 Tex Cotton/Polyester 42 Tex Cotton/Polyester X CD -P uB I oj W) r^ OJ (D f-i CQ O 32 Tex Cotton (x) 4-> 42 Tex Cotton (o) ?-i CD U-1 3. 8 4.0 4.2 4.4 4.6 Twist Multiple Figure 10. Effect of Twist Multiple on Yarn Energy to Break 37 42 Tex Cotton/Polyester u> 4-> •H e o MH •H on/Polyester :D x Cotton (x) 42 Tex Cotton (o) 6 7 Combing Roller Speed (ooo) Figure 11. Effect of Combing Roller Speed on Yarn Uniformity 38 and less tangled fibers. As the number of fiber clumps and tangles are reduced, uniformity improves. Ill.S.b. The Effect of Twist Multiple on Yarn Uniformity Figure 12 shows the effect of twist multiple on yarn uniformity. The 32 tex cotton, 42 tex cotton and 42 tex cotton/polyester showed lower uniformity as the twist multiple was increased while the 32 tex cotton/polyester had an increase. The twist multiple was increased by increasing the rotor speed while keeping throughout constant. Increased rotor speeds have been found to cause variations in yarn physical properties. Increases in rotor speed also cause an increase in the air velocity of the transport channel. Some fibers or blends may be subject to buckling or tangling in the transport channel when the velocity is increased. As tangling occurs there will be a reduction in evenness. III.5.C. Yarn Evenness and Strength In general, for open end spun yarns, there exists an inverse relationship between strength and evenness. Stated another way,as evenness increases,strength decreases. The strength evenness relationship observed for open end spun yarns is opposite of what is observed for ring spun yarns. The combing roller of the open end spinning frame is probably the cause of this inverse effect. The combing roller breaks the continuity of the fiber flow by pulling at fibers from a sliver. At higher combing roller speeds, fiber separation increases but there is also a corresponding increase in fiber 39 19 42 Tex Cotton (o) > 15 ^a 32 Te'x Cotton/Polyester (^ ) e ;-oi 2 Tex Cotton/Polyester i-M •H 'ZD 11 3. 8 4.0 4.2 4.4 4.6 Twist Multiple Figure 12. Effect of Twist Multiple on Yarn Lfniformity 40 breakage. The increased separation results in improved evenness while the increased fiber breakage results in reduced strength. III.6. Optimization of Open End Yarn Properties with Respect to Energy Consumption The basic premise behind optimizing yarn properties is that a particular level of a yarn property can be produced at different combinations of combing roller and rotor speeds. The results of testing yarn in this research shows that increased combing roller speeds and rotor speeds usually have opposite effects on yarn properties. Strength, elongation, and energy to break usually decrease with increased combing roller speeds but increase with increased rotor speeds. Uniformity improves with increasing combing roller speed while it decreases at increasing rotor speed. In order to formulate an optimization problem, the effects of the combing roller and rotor on yarn strength, elongation, energy to break, uniformity and power consump tion have to be determined at different combing roller and rotor speeds. Examining the data indicates that the best approximation for the model is planar; therefore, a multiple linear regression is used to model the effects of the machine parameters on yarn properties. Although there is considerable scatter in the actual data, the linear models are adequate because the primary purpose of this section is 41 to present a methodology for analyzing the yarn properties with respect to energy consumption and not to formulate exact mathematical models. Each yarn with a different linear density or fiber type which is spun is modeled separately. The general model is presented in Table 6 and the specific model for 42 tex cotton is presented in Table 7. The models in Tables 5 and 6 consist of five simultaneous equations. The object of this optimization is to minimize power consumption with respect to a given yarn property. The optimization problem for 42 tex cotton is formulated in Table 8. The requirements for the method used to solve this minimization are universal applicability to other textile processes, relative ease of use once the system is programmed on a computer, and flexibility, so that different questions can be answered without major program changes. Both linear and nonlinear programming are specialized and lack flexi bility. The method selected to solve these equations and determine the minimum energy consumption for a given yarn property is a conversational language which can solve simultaneous equations. The language is formally named "Question Answering System on Sets of Algebraic Equations, (QAS)." This system has the ability to store mathematical models and related data bases. Any conceivable question can be asked concerning the model instead of having to set up 7 different programs to solve particular problems (Appendix C). 42 Table 6. The General Model for Energy Consumption and Yarn Properties (TM = twist multiple, CRS = combing roller speed; A,B,C are coefficients computed using a multiple linear regression) A^(TM) + B^(CRS) + C^ = Strength A2(TM) + B2(CRS) + C2 = Elongation A^(TM) + B^(CRS) + C3 = Energy to break A^(TM) + B^(CRS) + C^ = Uniformity (%CV) A^(TM) + B^(CRS) + C^ = Energy consumption 43 Table 7. The Model for Energy Consumption and Yarn Properties of 42 Tex Cotton 987(TM) - .146(CRS) + .5039 = Strength 1095(TM) - .1177(CRS) + 9.052 = Elongation 0971(TM) - .0297(CRS) + .6025 = Energy to break 9840(TM) - .1033(CRS) + 10.28 = Uniformity (%CV) 2361(TM) + .0467(CRS) + .7461 = Energy consumption 44 Table 8. The Optimization Problem for 42 Tex Cotton Minimize: .2361(TM) + .0467(CRS) + .7461 = Energy consumption Subject to the restrictions: .9270(TM) - .1460(CRS) + 5.039 > x^ (strength) -.1095(TM) - .1177(CRS) + 9.032 > x^ (elongation) .0971(TM) - .0297(CRS) + .6025 > X3 (energy to break) .9840(TM) - .1033(CRS) + 10.28 > x^ (uniformity) 45 Minimization of energy consumption with respect to a particular yarn property is based on the premise that the particular property can be achieved at different combinations of combing roller and rotor speeds. In order to clarify this, a series of iso-graphs (Appendix D) are presented from data calculated using the "Question Answering System." Each iso-curve shows the different combinations of combing roller speeds and rotor speeds with which a given level of a particular yarn property can be achieved. Figures 13 through 16 show the iso-graphs for 42 tex cotton. The twist multiple is substituted for the rotor speed. Since throughput speed is held constant throughout this research, the twist multiple is linearly proportional to the rotor speed. In Figure 17, an iso-line for each property is combined onto one graph resulting in a hypothetical solution space. The optimal solution is the combination of combing roller speed and twist multiple in this solution space which yields the lowest energy consumption. Since decreases in combing roller speed increase strength, elongation and energy to break, the optimal solution for these parameters will always be at the lowest possible combing roller speed in the solution space. Optimal solutions with respect to strength, elonga tion, and energy to break can be found using QAS. After the optimal solution with respect to these parameters is found, uniformity can be computed. If it is acceptable, an optimal solution with respect to all four properties is found. If 46 Energy Consumption (kw-hrs/kg of yarn) Yarn Strength (g/tex) 8.7 g/tex .5 g/tex 3 g/tex 1 g/tex 2 kw - h r s / k, 1 kw-hrs/kg 6 7 Combing Roller Speed (ooo) Figure 13. Strength-Energy Iso-Curves for 42 Tex Cotton 47 Energy Consumption kw-hrs/kg of yarn % Elongation — 4. 8 2.2 kw-hrs/kg 2.1 kw-hrs/kg 5 6 7 Combing Roller Speed (ooo) I'igure 14. Elongation - Energy Iso Curves for 42 Tex Cotton 48 Energy Consumption (kw-hours/kg of yarn) Energy to Break (gram-cm/tex) 6 g-cm/tex / t,ex 80 g-cm/tex 7 g-cm/tex 2 kw-hrs/kg 1 kw-hrs/kg 6 7 Combing Roller Speed (ooo) I'igure 15. Energy to Break-Energy Iso-Curves for 42 Tex Cotton 49 Energy Consumption (kw-hrs/kg) Uniformity C%CV} —— 4. 8 17.5% 17. 3% \2 . 2 kw-hrs/kg 17.0% 16.8% .1 kw-hrs/kg 6 7 Combing Roller Speed (ooo) Figure 16. Un i formity-Fmergy Iso-Curves for 42 Tex Cotton 5 0 YARN STRENGTH :S:.':; YARN ENERGY TO BREAK;^ YARN ELONGATION YARN EVENNESS'/.;- 4 .8 "Oi.?.,***.-- . --. rtrryr .o . r j . •?; ;.-f •.; c.. ,., o'. *. 'o. '_» / , «».• .*; •.°''''.''^•- *•„'••••*.'.•;".• o-/".:'. •*. \r; :.°'-.-;'".'--v.°- •' •• *'. 'o- ../ _.« . .* o' ^, •*.-', ••*" ,,o* "-Q ;•.'•••/;•:•'. •". :«•>• '•." °.". .-•••> • • • •..'•'• - *.'. o -...-. • ,• *•' •; I »••• o. •-".•,» o ••. <" • ••.. • . • • • 6 7 Combing Roller Speed (ooo) I'igure 17. Solution Space for 42 Tex Cotton 51 it is not acceptable, there is no tractable solution for all properties and concessions in either strength, elongation or energy to break will have to be made if better uniformity is required. Energy consumption cannot be optimized with respect to uniformity and strength, elongation or energy to break because improvements in uniformity require lower twist multiples or higher combing roller speeds which result in reductions in strength, elongation and energy to break; however, if uniformity is paramount, energy consumption can be optimized with respect to uniformity alone. Figure 18 presents a flow chart showing how QAS is used to minimize energy consumption with respect to strength, elongation, and energy to break. It also maps out an iterative procedure which can be used to make trade-offs between strength and evenness. Each block contains the commands required to do the underlined step in that block. Figure 19 is an illustration of the minimization of energy consumption using the flow chart presented in Figure 18. It also illustrates how the iterative procedure is used to trade off strength for evenness. The flow chart (Figure 18) can be divided into three main sections. Blocks 1 to 5 compute the combination of combing roller and rotor speed which minimize energy consump tion with respect to strength, elongation and energy to break They also compute the resulting evenness. If the evenness in block 7 is satisfactory, no further computing is necessary. 52 OPTiMizii YS-YI:X-I:TB A[ VS-requi red. CRS 5 AO r.NC, TM If TM is within I f 'I'M not wi thin can;ilii 1 i ty of i:i;ichina Nil. capability of machine >i; —^ RKSOITS 3k coMi'inr. vc r„\c TM COMPlJrn NHIV TM RI YS AI TM optimal RI CRS AO vc; AI TM within capability closest to original TM ^ RliSllLTS VC r.N'C If XC not Acccj)tal)lc \k- coMi'irrr, CRS THAT KOiJi.nGivn DiiSiRni) vc V Al vc Desired RI CRS RO VC AO CRS sroi' Key: YS Strength AI Assign to Input YEX Elongation AO Assign to Output ETB Energy to Break RI Remove from Input VC Uniformity RO Remove from Output Figure 18 Flowchart for Minimizing Energy Consumption Considering Strength, Elongation, Energy to Break and Uniformity 53 AI MT C0T14 ? AI YS 8.5,CRS 5 ? AO ENC,TM;EX RESULTS: RESULTS: ENC 1.9821E+00 ENC 2.2877E+00 TM 4.2462E+00 CRS 8.7438E+00 ? RI YS ? AI CRS 8743*DEL* ? AI TM 4.2462 AI CRS 8.7438 ? RO TM ? RI YS ? AO VC;EX ? AO VC RESULTS ? RO CRS ENC 1.9821E+00 ?O TE' X"VT" VC 1.3942E+01 RESULTS: ? AI VC 13 ENC 2.2877E+00 ? RI CRS VC 1.4100E+01 ? RO VC ? AO YS,YEX,ETB,VC;E, X ? AO CRS;EX RESULTS: RESULTS ENC 2.2877E+00 ENC 2.4079E+00 VC 1.4100E+01 CRS 1.4117E+01 YS 8.5000E+00 ? RI VC YEX 7.4773E+00 ? AI CRS 14 ETB 8.0889E-01 ? AO YS ? RO CRS;EX RESULTS: ENC 2.4024E+00 YS 7.1860E+00 ? AI YS 8.5 ? RI TM ? AO TM ? RO YS ? RO CRS;EX RESULTS: ENC 2.7167E+00 TM S.5775E+00 ? RI CRS ? AI TM 4.8 ? RO TM ? AO CRS Figure 19. Minimization o£ Energy Consumption with Respect to Strength Elongation and Energy to Break 54 The energy consumption at this point is minimized. If the evenness in block 4 is not acceptable, blocks 6 through 9 can be used to decrease %CV to an acceptable level by computing a higher combing roller speed; however, the reduc tions in %CV will be accompanied by decreases in strength, elongation and energy to break. If by reducing %CV, the yarn strength falls below an acceptable level, blocks 10 through 14 will compute a higher twist multiple which would increase strength while slightly decreasing evenness. The energy consumption computed at each step is optimal for the condi tions imposed. If uniformity is paramount, QAS can minimize energy consumption with respect to uniformity alone. This is accomplished by assigning to input (AI) the desired evenness (VC) and the lowest twist multiple (TM), while assigning to output (AO) energy consumption (ENC) and combing roller speed (CRS). If the combing roller speed computed is within the spinning range of the open end frame and the fiber type, energy consumption is minimized with respect to uniformity. If the speed is out of range, the desired evenness cannot be achieved for the particular material (Figure 20). 55 /AT,QAS/UN=LIBRARY /QAS ? DF ENCOl ? AI VC 13,TM 3.8 MT C0T14; AO ENC,CRS;EX RESULTS: ENC 2.1249E+00 CRS 9.8664E+00 Figure 20. Minimization of Energy Consumption with Respect to Uniformity 56 CHAPTER IV CONCLUSIONS The laboratory open end spinning frame built at Georgia Tech produces yarn of production quality. Increasing the combing roller speed generally decreases yarn strength, elongation, energy to break and increases evenness and energy consumption. Increasing the twist multiple increases strength, elongation, energy to break, energy consumption and decreases evenness. Increasing rotor speed, increases twist but also has a negative effect on all yarn properties. The degree that the properties of a particular yarn will be affected by changes in the combing roller or rotor speed is dependent on the type of fiber or fiber blend being spun. Longer fiber lengths or higher coefficients of friction between fibers will require a higher combing force which results in a higher percentage of broken fibers. Fibers with higher torsional rigidities and larger yarn linear densities produce higher reactions to the turning moment of the rotor resulting in lower twist efficiency. This results in lower than expected strength, elongation, energy to break and improved evenness. A given level of strength, elongation, energy to break or uniformity can be achieved at different combinations 57 of combing roller and rotor speeds. Since lower speeds result in lower energy consumption, the properties of open end spun yarn can be optimized with respect to energy consumption by finding the lowest combing roller and rotor speed combination that produce yarn of acceptable strength, elongation, energy to break and uniformity. CHAPTER V RECOMMENDATIONS For open end spinning, extensive efforts are needed to investigate and model the effect of different fiber types and staple lengths on yarn properties at different combina tions of combing roller and rotor speeds. Such work leads to findings that show different optimum combing roller and rotor speeds for each fiber and staple length. In addition, more research in textile manufacturing needs to be directed to optimizing energy consumption with output and quality. This research shows that optimizing energy consumption and quality is possible for the open end spinning process. However, more extensive investigations are needed in open end spinning as well as most other wet and dry textile processes. 59 APPENDIX A YARN TEST RESULTS 60 Table 9. Yarn Tensile Strength for 32 Tex Cotton (gms/tex) Twist Multiple 3. 4.3 4.7 Combing Roller 5000 8.6 10.0 12.0 6000 7.9 9.2 11.0 7000 8. 3 9.4 11.0 8000 8.1 9.2 11.0 9000 8.4 9.0 11.0 Table 10. Percent Elongation for 32 Tex Cotton Twist Multiple 3.8 4.3 4.7 Combing Roller rpm 5000 8. 3 8.6 9.1 6000 7.6 8.1 8.9 7000 7.9 8.1 8.4 8000 8.0 7.9 8.0 9000 7.9 8.1 8.3 61 Table 11. Energy to Break for 32 Tex Cotton (gm-cm/tex) Twist Multiple 3. 4.3 4.7 Combing Roller rpm 5000 .90 1.1 1.2 6000 . 79 .95 1.1 7000 .83 .97 1.1 8000 .83 .92 1.0 9000 .85 .92 1.0 Table 12. %OJ for 32 Tex Cotton Twist Multiple 3.8 4.3 4.7 Combing Roller rpm 5000 12.8 13.9 14.6 6000 12.9 13.5 14.1 7000 12.4 12.5 13.3 8000 11.3 12.5 13.0 9000 11.5 12.4 12 .6 62 Table 13. Yarn Tensile Strength for 42 Tex Cotton Yarn (gms/tex) Twist Multiple 3.8 4.3 4.7 Combing Roller rpm 5000 8.2 8.8 8.4 6000 7.8 8.5 9.1 7000 7.7 8.2 8.8 8000 7.8 7.8 8.6 9000 7. 3 8.2 8. 3 Table 14. Percent Elongation for 42 Tex Cotton Twist Multiple 3.8 4.3 4.7 Combing Roller rpm 5000 7.9 7.8 8.9 6000 7.5 7.5 8.1 7000 7.9 7.4 7.1 8000 8.2 7.4 7.7 9000 8.0 7.4 7. 3 I 63 Table 15. Energy to Break for 42 Tex Cotton (gm-cm/tex) Twist Multiple 3.8 4.3 4.7 Combing Roller rpm 5000 .82 .85 .96 6000 .74 .80 .99 7000 . 77 . 76 .80 8000 .82 .71 .85 9000 .74 .76 .76 Table 16. %CV for 42 Tex Cotton Twist Multiple 3.8 4.3 4.7 Combing Roller rpm 5000 12.6 12.8 13.6 6000 11.6 12.5 12.4 i 7000 13.6 12.4 12.3 8000 12.3 11.5 12.4 I 9000 12.3 12.6 12.4 64 Table 17. Yarn Tensile Strength for 32 Tex 65^0 Polyester/35% Cotton (gms/tex) Twist Multiple 4.1 4.4 4.7 Combing Roller rpm 7000 13.8 13.8 15.8 8000 13.2 13.8 15.2 9000 12.8 13.1 14.8 Table 18. Percent Elongation for 32 Tex 65% Polyester/35% Cotton Twist Multiple 4.1 4.4 4. 7 Combing Roller rpm 7000 15.4 15.5 15.7 8000 14.8 14. 7 14.9 9000 13.1 14.3 14.2 65 Table 19. Energy to Break for 32 Tex 65^ Polyester/35% Cotton (gm-cm/tex) Twist Multiple 4.1 4.4 4.7 Combing Roller rpm 7000 2.70 2.71 2. 11 8000 2.48 2.57 2.74 9000 2.13 2.58 2.74 Table 20. ICV for 32 Tex 65% Polyester/35% Cotton Twist Multiple 4.1 4.4 4.7 Combing Roller rpm 7000 15.9 14.1 14.4 8000 12.3 12.8 13.1 9000 12.4 12.5 12.9 66 Table 21. Yarn Tensile Strength for 42 Tex 65% Polyester/35% Cotton (gms/tex) Twist Multiple 4.1 4.4 4.7 Combing Roller rpm 7000 12.7 11.9 11.9 8000 12.6 13.5 11.2 9000 12.4 12.4 11.6 Table 22. Percent Elongation for 42 Tex 651 Polyester/35% Cotton Twist Multiple 4.1 4.4 4.7 Combing Roller rpm 7000 14.8 13.6 14.9 8000 14.5 17.7 13.3 9000 15.3 14.2 11.6 67 Table 23. Energy to Break for 42 Tex 6S% Polyester/35% Cotton Twist Multiple 4.1 4.4 4.7 Combing Roller rpm 7000 2.00 2.06 2.25 8000 2.33 3.05 1.89 1 9000 2.42 2.22 1.98 Table 24. ICV for 42 Tex 65% Polyester/35% Cotton Twist Multiple 4.1 4.4 4.7 Combing Roller rpm 7000 12.8 11.9 14.4 8000 12.3 12.3 12.5 9000 11.1 12.4 12.8 68 APPENDIX B ENERGY CONSUMPTION MEASUREMENTS 69 on tn ^ •<:f LO m o ' o LO (NJ (NJ CsJ (NJ CsJ -^ l-O r-- r—1 (NJ CTi (NJ to to to "^ o • o • (NJ• \ to cn o r—1 r—1 CNJ OJO to '=:•t (NJ to to to to •H •H r-- r—1 (NJ CNJ to to DH o • CO o •=:t (NJ CM (N CNJ CNJ LO 00 cn cn o r-H w (NJ CM CM to to a LO CSJ X o o O O o APPENDIX C QAS PROGRAM 71 ENCOL -- ENERGY CONSUMPTION IN OPEN END SPINNING 23 16 1 1 YS YARN STRENGTH 2 YEX YARN EXTENSION 3 ETB YARN ENERGY TO BREAK 4 VC LINEAR DENSITY VARIATION COEFFICIENT 5 ENC ENERGY CONSUMPTION 6 TM TWIST MULTIPLIER 7 CRS COMBING ROLLER SPEED 8 Al MULTIPLE REGRESSION COEFFICIENT 9 Bl 10 CI 11 A2 12 B2 13 C2 14 A3 15 B3 16 C3 17 A4 18 B4 19 C4 20 A5 TYPE OF YARN 21 B5 22 YS=A1*TM+B1*CRS+CC5 1 23 MYEX=A2*TM+B2*CRS+CT 2 1 ETB=A3*TM+B3*CRS+C3 2 VC=A4*TM+B4*CRS+C4 3 ENC=A5*TM+B5*CRS+C5 4 CA1*B2-A2*B1)*CRS=A2*(C1-YS)+A1*(YEX-C2) NN5P DATA BASE FOR ENCOl 6 1 4 15 Al Bl CI A2 B2 C2 C0T14 9.870E-01 -1 460E-01 039E+00 -1.095E-01-1 177E-01 032E+00 C0T18 2.996E+00 1.847E-01- 947E+00 6.682E-01-1 280E-01 256E+00 C/P14 -1.668E+00 1.670E-02 971E+01 -2.667E+00-3 667E-01 910E+01 C/P18 3.333E+00 -4 500E-01 967E+00 8.333E-01-8 333E-01 773E+01 A3 B3 C3 A4 B4 C4 C0T14 9.710E-02 -2 970E-02 6.025E-01 9.840E-01-1 033E-01 1.028E+01 C0T18 2.610E-01 2.820E-02 4.520E-02 1.225E+00-3 533E-01 7.548E+00 C/P14 -3.500E-01 5.170E-02 3.371E+00 1.556E+00-3.667E-01 6.067E+00 C/P18 5.222E-01 1.217E-01 1.278E+00 -5.560E-02- 8.333E-01 1.757E+01 A5 B5 C5 C0T14 .2361E+00 .0467E+00 .7461E+00 C0T18 .5820E+00 .0633E+00 .8030E-01 C/P14 .3889E+00 .0500E+00 .0333E+00 C/P18 .5000E+00 .0833E+00 .2778E+00 72 APPENDIX D ISO-GRAPHS FOR ENERGY CONSUMPTION AND YARN PROPERTIES 73 Energy Consumption (kw-hrs/kg of yarn) Yarn Strength (grams/tex) 4. 8 \ 11.6 g/tex \ \ \ 4.6 -^ 11.9 g/tex \ \ \ \ •\2.2 kw-hrs/kg a, 4.4 •^x- —^ 12. 2 g/tex •M i-H Z3 \ \ IS) •H 12.5 g/tex i 4.2 \ \ \ "2.1 kw-hrs/kg \ 4.0 2.0 kw-hrs/kg 3. 8 6 7 8 Combing Roller Speed (ooo) Figure 21. Strength-Energy Iso-Curves for 42 Tex Cotton/Polyester 74 Knergy Consumption (kw-hrs/kg of yarn) Percent Elongation CD I—( 2 kw-hrs/kg P. •M 4-^ ,—i <^ •M 14.5% f) 1 kw-hrs/kg 15.01 2.0 kw-hrs/kg 15.51 6 7 Combing Roller Speed (ooo) I'igurc 22. Percent Elongation-Energy Iso-Curves for 42 Tex Cotton/Polyester 75 Energy Consumption (kw-hrs/kg of yarnl Energy to Break (gram-centimeters/tex) 4.8 2.16 g-cm/tex .22 g-cm/tex .2 8 g-cm/tex .2 kw-hrs/kg .34 g-cm/tex . 1 kw-hrs/kg .0 kw-hrs/kg 6 7 8 Combing Roller Speed (ooo) Figure 23. Energy to Break-Energy Iso-Curves for 42 Tex Cotton/Polyester 76 Energy Consumption (kw-hrs/kg of yarn) Uniformity (%CV) 13.3% 12.9% 12.5% I—I 12.1% 2 kw-hrs/kg -P t/) • H '7' 1 kw-hrs/kg 4.0 /-« 0 kw-hrs/kg 6 7 Combing Roller Speed (ooo) Figure 24. Uniformity-Energy Iso-Curves for 42 Tex Cotton/Polyester 77 Energy Consumption (kw-hrs/kg of yarn) Yarn Strength (grams/tex)— 10.5 g/tex 9.9 g/tex 2 kw-hrs/kg .3 g/tex 8.7 g/tex 0 kw-hrs/kg - > 6 7 Combing Roller Speed (ooo) rigure 25. Strength-Energy Iso-Curves for 32 Tex Cotton Energy Consumption (kw-hrs/kg of yarn) Percent Elongation—• 8.51 4. 8 8. 3% 2 kw-hrs/kg 0 kw-hrs/kg 6 7 8 9 Combing Roller Speed (ooo) I'igure 26. Elongation-Energy Iso-Curve for 32 Tex Cotton 79 Energy Consumption (kw-hrs/kg of yarn) Energy to Break (gram-centimeters/tex) .99 g-cm/tex i 96 g-cm/tex 2 kw-hrs/kg 93 g-cm/tex 90 g-cm/tex "3.0 kw-hrs/kg 2.8 kw-hrs/kg 0 7 8 Combing Roller Speed (ooo) Figure 27. Energy to Break-Energy Iso Curves for 32 Tex Cotton 80 Energy Consumption (kw-hrs/kg of yarn) Uniformity (%CV)— — 13.4% 13.1% 12.9% 12.6% 4.8 4.6 (D r—t CL •M •M 4.4 4-> ir, -hrs/kg H 4.2 4.0 -hrs/kg 3.8 6 7 Combing Roller Speed (ooo) Figure 28. Uniformity-Energy Iso-Curves for 32 Tex Cotton Imergy Consumption fkw-hrs/kg of yarn) Yarn Strength (grams/tex) 4.8 15.2 g/tex 14.6 g/tex 14 g/tex 3.2 kw-hrs/k, 3.4 g/tex 0 kw-hrs/kg 6 7 Combing Roller Speed (ooo) Figure 29. Strength-Energy Iso-Curves for 32 Tex Cotton/Polyester 82 Imergy Consumption (kw-hrs/kg) Percent Elongation — 16.8% 16 . 0 ?6 15.2% 14.41 QJ OH -^^ +-) m 3.2 kw-hrs/kg •H [2 3.0 kw-hrs/kg 6 7 Combing Roller Speed (ooo) Figure 30. Elongation-Energy Iso Curves for 32 Tex Cotton/Polyester 8 3 J:nergy Consumption (kw-hrs/kg of yarn) Energy to Break (gram-centimeters/tex) 2.76 g-cm/tex 2.68 g-cm/tex 2.62 g-cm/tex 2.56 g-cm/tex (U r—I • H •!-> r-^ :^ 'Jt • H 3.2 kw-hrs/kg 3.0 kw-hrs/kg Figure 31. Energy to Break-Energy Iso-Curves for 32 Tex Cotton/Polyester 84 BIBLIOGRAPHY 1. Wanner, W., "Energy Questions in Spinning," International Textile Bulletin, March, 1975. 2. Dyson, E., "A Study of Open End Spinning by Circumfer ential Assembly, with Special Reference to the Spinning of Modified Rayon," Part II: Fiber Assembly, Journal of the Textile Institute, Volume 74, p. 632-638. 3. Dyson, E., "A Study of Open End Spinning by Circumfer ential Assembly, with Special Reference to the Spinning of Modified Rayon," Part I: Fiber Presentation, Journal of the Textile Institute, Volume 69, p. 588-594. 4. Tooke, T., "Technical Background of Toyoda Open End Spinning Machine," Toyoda Automatic Loom Works, Japan. 5. Vaughn, E. A. and T. Hiranprueck, "The Effect of Certain Machine Parameters and Fiber Preparation on the Properties of Open-End Cotton Yarns," ASME Paper No. 75 Tex-4. 6. Stalder, H., "Influence of the Rotor Speed on the Yarn Manufacturing Process," Rei-ter Machine Works Ltd., Switzerland. 7. Konopasek, M. , "An Advanced Question Answering System on Sets of Algebraic Equations," School of Textile Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332. 8. Lord, P. R. and P. C. Grady, "The Twist Structure of Open End Yarns," Volume 46, Textile Research Journal, 1976, 9. Vaughn, E. A. and T. S. Cox, "The Effects of Opening Roller Wire Design and Operating Properties of Open End Cotton Yarn," ASME Paper No. 75 Tex-4.