Cell Loading and Scheduling in a Shoe Manufacturing Company A thesis presented to the faculty of the Fritz J. and Dolores H Russ College of Engineering and Technology of Ohio University In partial fulfillment of the requirements for the degree Master of Science Ananthanarayanan K. Subramanian November 2004 This thesis entitled CELL LOADING AND SCHEDULING IN A SHOE MANUFACTURING COMPANY by ANANTHANARAYANAN K. SUBRAMANIAN has been approved for the Department of Industrial and Manufacturing Systems Engineering and the Russ College of Engineering and Technology by Gürsel A. Süer Professor of Industrial and Manufacturing Systems Engineering Dennis Irwin Dean, Fritz J. and Dolores H. Russ College of Engineering and Technology SUBRAMANIAN, ANANTHANARAYANAN. K. MS. November 2004. Industrial and Manufacturing Systems Engineering. Cell Loading and Scheduling in a Shoe Manufacturing Company (130 pp.) Director of Thesis: Gürsel A. Süer This thesis focuses on a complex cell loading and scheduling problem at a shoe manufacturing facility. A set of four cell loading heuristics, namely – Do Not Split, Split as and when required, and Split Only When Load Greater than MaxCap, were developed and augmented with a simple cell scheduling methodology. The objective of the heuristic procedures is to ensure that all the jobs are loaded without exceeding the given capacity. The heuristics can also be used to minimize makespan by carefully defining certain parameters. The heuristics are encoded using VB 6.0 and a software application was created to test and compare the heuristics. These heuristics are compared with respect to completed jobs, makespan and setup times. Overall, after the cell loading stage, the Split as and when required heuristic can recommended as the best. But the optimal result from the cell loading stage might not be so at the end of the cell scheduling stage. The choice of heuristics is also driven by the conditions that the user is faced with like overtime costs, machine breakdowns etc. Hence the heuristics have to be repeatedly applied after varying inputs until an optimal result appears at the end of the scheduling stage. However this is not a tedious process given the processing speed of the software application. Approved: Gürsel A. Süer Professor of Industrial and Manufacturing Systems Engineering Dedication This thesis is dedicated to the people who have supported me all the way in my life - my mother Vasantha, my father Subramanian, my sister Preethi, my teachers, my advisor Dr. Gürsel A. Süer, my committee members and all my friends from high school and college in India and in the USA. 5 Table of Contents CHAPTER 1. INTRODUCTION ............................................................................13 1.1 Group Technology .........................................................................................13 1.2 Manufacturing Systems..................................................................................14 1.2.1 Dedicated Production Line .........................................................................15 1.2.2 Job Shop ....................................................................................................16 1.2.3 Manufacturing Cells...................................................................................16 1.2.4 Fixed Layouts.............................................................................................16 1.3 Cellular Manufacturing Systems (CMS).........................................................17 1.4 Cellular Manufacturing System Configurations:.............................................18 1.4.1 Independent Cells.......................................................................................18 1.4.2 Connected Cells .........................................................................................19 1.5 Production Control in Cellular Manufacturing Systems..................................22 1.5.1 Cell Loading...............................................................................................22 1.5.2 Cell Scheduling ..........................................................................................23 1.6 Solution Techniques.......................................................................................24 1.6.1 Optimizing Procedures...............................................................................25 1.6.2 Heuristics ...................................................................................................25 1.6.3 Meta-Heuristics..........................................................................................25 1.7 Computer Programming Language – Visual Basic..........................................26 1.8 Thesis Objectives ...........................................................................................27 1.9 Organization of This Thesis ...........................................................................28 CHAPTER 2. LITERATURE REVIEW.................................................................29 CHAPTER 3. PROBLEM STATEMENT ..............................................................40 3.1 A Typical Cell group......................................................................................40 3.2 Current Cellular Configuration.......................................................................40 6 3.3 The Jobs.........................................................................................................42 3.4 The Rotary Machine Cell ...............................................................................42 3.5 Rotary machine operation – Loading Shoes....................................................43 3.6 Molds.............................................................................................................48 3.7 Processing Times ...........................................................................................49 3.8 Special Considerations in the Cell loading Phase............................................51 3.8.1 The Loading Procedure ..............................................................................51 3.8.2 MaxCap .....................................................................................................52 3.8.3 The Shared Cell..........................................................................................53 CHAPTER 4. METHODOLOGY...........................................................................54 4.1 Phase I-A: Demand Aggregation and Number of Cells Determination............54 4.1.1 Data Input ..................................................................................................56 4.1.2 Grouping of Products in Super-families......................................................56 4.1.3 Calculations of Total Processing Times......................................................58 4.1.4 Calculation of the number of cells of each type...........................................61 4.2 Phase I-B – Family Definition........................................................................63 4.2.1 Calculation of family processing times .......................................................67 4.2.2 Arranging Families in LPT.........................................................................67 4.3 Phase II – Cell Loading ..................................................................................69 4.3.1 Do not Split Families:.................................................................................70 4.3.2 Lot splitting allowed as and when required.................................................76 4.3.3 Split families only when load is greater than MaxCap ................................83 4.3.4 Load Jobs First Into the Cells and Then Form Families Independently .......90 4.4 Scheduling of Families and Jobs.....................................................................96 4.5 The Cell Loading And Cell Scheduling (CLACS) Application .....................102 CHAPTER 5. ANALYSIS OF RESULTS.............................................................109 5.1 Experimental Conditions ..............................................................................109 5.2 Comparison of cell loading heuristics...........................................................111 7 5.3 Effects of MaxCap on Makespan (lower bound)...........................................113 5.4 Effects of MaxCap on Makespan (upper bound)...........................................115 5.5 Comparison of cell idle times .......................................................................116 5.6 Comparison of Makespan (number of families) ............................................120 CHAPTER 6. CONCLUSIONS AND FUTURE WORK .....................................122 6.1 Conclusions..................................................................................................122 6.2 Future Work.................................................................................................124 BIBLIOGRAPHY......................................................................................................126 8 List of Tables Table 3-1: Sample list of jobs ........................................................................................43 Table 3-2: Processing Times..........................................................................................50 Table 4-1: Typical data..................................................................................................57 Table 4-2: Jobs divided into super-families (Sample).....................................................59