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X. Supporting Slides. Systems for Planning & Control in Manufacturing: Systems and Management for Competitive Manufacture. Professor David K Harrison Glasgow Caledonian University Dr David J Petty The University of Manchester Institute of Science and Technology. ISBN 0 7506 49771. 0000.

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  1. X Supporting Slides Systems for Planning & Control in Manufacturing: Systems and Management for Competitive Manufacture Professor David K Harrison Glasgow Caledonian University Dr David J Petty The University of Manchester Institute of Science and Technology ISBN 0 7506 49771 0000

  2. 19 Finite Capacity Scheduling (FCS) • Doubts Over MRPII by 1980's • Use of JIT Techniques • Development of OPT by Goldratt in 1970's • Publication of "The Goal" • Marketing of the OPT Software Package • This Section Will Examine FCS, ICS and OPT 1901

  3. 19 MRP Limitations Job A Quantity 100 Due Date 07/10 Total Time to Manufacture A = 11.33Hrs Operation 10 Work Centre 001 Set Time 60 Mins Total Time to Manufacture B = 12.17Hrs Unit Time 2 Mins 20 Work Centre 002 Set Time 120 Mins Unit Time 3 Mins Job B Quantity 100 What is the Best Sequence for Manufacture? Due Date 07/10 Operation 10 Work Centre 001 Set Time 120 Mins Unit Time 4 Mins 20 Work Centre 002 Set Time 60 Mins Unit Time 1.5 Mins MRP Assumptions: Work Work Centre Centre Fixed Lot Sizes 001 002 Fixed Lead Times 1902

  4. Time Base Time Base MRP - Infinite, Backward FCS - Finite, Forward Scheduling Method Scheduling Method 19 Finite and Infinite Scheduling MRP - Assumes Dominant Queuing Time Start Start Due Due Now Now Date Date Date Date Lead Time 1903

  5. 19 Data 1 – Workcentres Forging 1 M/C 8 Hours 2 Shift Efficiency £50/Hr Press in Group per Shift Pattern Factor: 90% 1029 1 M/C 8 Hours 2 Shift Efficiency £40/Hr Lathe in Group per Shift Pattern Factor: 90% 1013 Vertical 1 M/C 8 Hours 2 Shift Efficiency £45/Hr Mill in Group per Shift Pattern Factor: 90% 1019 1 M/C 8 Hours 2 Shift Efficiency £25/Hr Drill in Group per Shift Pattern Factor: 90% 1023 1904

  6. 19 Data 2 - Routings Item Number: GDS8975T Operation 10 Operation 20 Operation 30 Operation 40 W/C 1029 W/C 1013 W/C 1019 W/C 1023 Ts = 90 Mins Ts = 45 Mins Ts = 80 Mins Ts = 90 Mins Tp = 3 Mins Tp = 2 Mins Tp = 2 Mins Tp = 2 Mins Tm = 240 Mins Tm = 240 Mins Tm = 240 Mins Tm = 240 Mins Tq = 480 Mins Tq = 480 Mins Tq = 480 Mins Tq = 480 Mins Mill slots and inlet Drill 15 holes, Turn complete to Set press to 15T. pockets to evenly spaced. drawing. Use NC drawing. Use NC tape number tape 1264-9888. 1938-0484. 1905

  7. Op 1. Op 2. Op 4. Op 4. R1 R2 Op 1. Op 1. R1 Op 2. Op 2. R2 Op 3. Op 3. R4 Op 4. R4 R1 R3 Op 4. R5 Op 1. Op 2. Op 3. R5 R1 R4 R6 Op 1. R6 Op 2. R4 Op 3. R2 R1 Op 1. Op 2. Op 3. Op 4. R2 R3 R5 R4 R6 R6 Op 3. R3 R1 R3 R5 R5 Op 4. Op 4. R2 R4 R6 19 Example Routing Job 1 Job 2 Job 3 Job 4 Job 5 Job 6 Op. = Operation R = Resource Operation 4 on Resource 6 1906

  8. Op 1. R1 Op 4. Op 1. Op 2. R2 Op 4. R1 Op 2. R2 Op 1. Op 1. R1 Op 2. R2 R2 Op 3. R4 Op 2. R4 Op 2. Op 2. Op 3. Op 3. Op 3. Op 4. Op 4. R4 R1 R1 R3 Op 4. R5 R3 R5 Op 4. Op 1. R5 R6 Op 1. Op 2. R1 Op 3. R5 Op 2. R1 R4 R4 R6 Op 3. Op 1. R6 Op 2. R4 Op 3. Op 1. Op 3. R2 R1 R6 Op 2. R4 R2 R1 Op 1. R2 R3 R5 R4 Op 1. R2 Op 2. Op 2. R3 Op 3. Op 3. R5 Op 4. Op 4. R4 R6 R6 Op 3. Op 3. R3 R3 R5 R5 Op 4. Op 4. Op 4. Op 4. Op 1. 19 Infinite Scheduling - Example Start Date Due Date Op 1. Op 2. Op 3. Op 4. Job 1 Job 1 Job 2 Job 2 Job 3 Job 3 Job 4 Job 4 Job 5 Job 6 Job 5 Job 6 Lead Time Load Hrs Load Hrs Load Hrs Load Hrs Load Hrs Load Hrs R1 R2 R3 R4 R5 R6 Cap. Cap. Cap. Cap. Cap. Cap. R1 Overload Overload R4 Op 1. 5 6 7 8 5 6 7 8 5 6 7 8 5 6 7 8 5 6 7 8 5 6 7 8 Time (Days) Time (Days) Time (Days) Time (Days) Time (Days) Time (Days) 1907

  9. 19 Infinite Scheduling - Key Points • Jobs Never Late by Definition • Problems Shown by Overloads • Does not Provide Solutions • Called CRP with MRPII/ERP 1908

  10. 19 Finite Capacity Scheduling (1) • Different Methods Available • Computers Commonly Used • Manual Methods (e.g. Gantt Charts) Available • Determine Priority Sequence • Load Jobs Progressively • Optimise Schedule General Approach 1909

  11. Op 1. Op 2. R2 Op 4. R1 Op 1. Op 1. R1 Op 2. Op 2. R2 Op 3. Op 3. R4 Op 4. R5 R4 R1 R3 Op 4. Op 1. R5 Op 3. R4 R6 Op 2. R1 Op 1. R6 Op 2. R4 Op 3. R2 R1 Op 1. R2 Op 2. R3 Op 3. Op 4. R4 R5 R6 Op 3. R3 R5 Op 4. Op 4. 19 Finite Capacity Scheduling (2) Job 1 Job 2 Job 3 Job 4 Job 5 Job 6 Time R1 R2 R3 R4 R5 R6 1910

  12. Op 1. Op 1. Op 2. R2 Op 4. Op 1. R1 R1 R1 Op 2. Op 4. R2 Op 1. Op 1. R1 Op 2. Op 2. R2 Op 3. Op 3. R4 Op 4. R5 R4 R1 R3 Op 4. Op 1. R5 Op 3. R4 R6 Op 2. R1 Op 1. R6 Op 2. R4 Op 3. R2 R1 Op 1. R2 Op 2. R3 Op 3. Op 4. R4 R5 R6 R6 Op 3. Op 3. R3 R3 R5 Op 4. Op 4. 19 Finite Capacity Scheduling (3) Job 1 Job 2 Job 3 Job 4 Job 5 Job 6 Time R1 R2 R3 R4 R5 R6 1911

  13. Op 1. Op 2. R2 Op 4. Op 1. R1 R1 Op 2. Op 4. R2 R1 Op 1. Op 4. Op 1. Op 1. R1 Op 2. Op 2. Op 2. R2 R2 Op 3. Op 3. Op 3. R4 R4 Op 4. R5 R4 R1 R3 Op 4. Op 1. R5 Op 3. R4 R6 Op 2. R1 Op 1. R6 Op 2. R4 Op 3. R2 R1 Op 1. R2 Op 2. R3 Op 3. Op 4. R4 R5 R6 R6 Op 3. Op 3. R3 R3 R5 R5 Op 4. Op 4. 19 Finite Capacity Scheduling (4) Job 1 Job 2 Job 3 Job 4 Job 5 Job 6 Time R1 R2 R3 R4 R5 R6 1912

  14. Op 1. Op 2. Op 4. Op 1. R1 R2 R1 Op 2. Op 4. R2 R1 Op 3. Op 1. Op 2. Op 4. Op 1. Op 1. Op 1. R1 Op 2. Op 2. Op 2. R2 R2 Op 3. Op 3. Op 3. R4 R4 Op 4. R5 R1 R3 Op 4. R4 R4 R1 R3 Op 4. R5 Op 1. Op 2. Op 3. Op 1. R5 R5 R1 R4 R6 Op 2. Op 3. R1 R4 R6 R1 Op 1. Op 1. R6 R6 Op 2. Op 2. R4 R4 Op 3. Op 3. R2 R2 R1 Op 2. R3 Op 3. Op 1. Op 1. Op 2. Op 3. R5 Op 4. Op 4. R2 R2 R3 R5 R4 R4 R6 R6 Op 3. Op 3. R3 R3 R5 R5 Op 4. Op 4. Op 4. Op 4. 19 Finite Capacity Scheduling (5) Job 1 Job 2 Job 3 Job 4 Job 5 Job 6 Time R1 R2 R3 R4 R5 R6 1913

  15. 19 Finite Scheduling - Key Points • Resources Never Overloaded • Problems Shown by Lateness • Ignores Subjective Factors 1914

  16. Op 1. Op 2. R2 Op 4. R1 R1 Op 1. Op 1. Op 2. Op 2. R2 Op 3. R4 Op 4. Op 3. R4 R1 Op 4. R5 R3 Op 3. R4 Op 2. Op 1. R1 R6 R5 R6 Op 2. R1 R4 Op 1. Op 3. R2 Op 4. Op 1. Op 2. Op 3. R4 R2 R5 R3 R6 Op 3. R3 R5 Op 4. Op 4. 19 Schedule Optimisation Time R1 R2 R3 R4 R5 R6 Idle Queue • Is this the Best Schedule? • Objective Functions • Permutations = mn • Minimum Makespan • Minimum Tardiness • Maximum Profit 1915

  17. List Jobs and Times Finish Select Smallest Time Last Job? Place as Near to Beginning as Possible Occurs at Machine 1? Place as Near to End as Possible 19 Johnson’s Algorithm Which Sequence Will Minimise Makespan? Machine 1 Machine 2 Queue Yes No Machine Job Time (1) Time (2) Seq. 6 A 7 5 B 4 11 C 5 Yes 4 D 8 9 E 12 10 F 13 No 13 G 9 7 H 10 8 I 9 8 J 6 1916

  18. 19 Work-to-Lists MRP Due Back Scheduling • Issued to Each Work Centre • Means of Detailed Control • Issued Daily Date Op 40 Logic Op 30 Op 20 Op 10 MRP Start Date Prioritisation Rules Work Centre Centre Lathes Issue Date 17/04/05 0290 Order Due Part Operation Due Next Work Previous Work Order Quantity Due Date Centre Number Number Date Work Centre 3000167 GOS1365 1000 18/04/05 06/05/05 0360 0370 3000369 GDS1987 1000 18/04/05 07/05/05 0360 0370 3000258 PFF1888 1000 18/04/05 12/05/05 0380 0410 3000198 TDS3687 1000 18/04/05 16/05/05 0360 0370 3000153 TDS9637 1000 19/04/05 17/05/05 0360 0420 1917

  19. 19 Prioritisation and Sequencing – 1 m n Time Available (T ) Due Today a • Static Rules • SPT* • EDD* • LPT 1918

  20. 19 Prioritisation and Sequencing – 2 m n Time Available (T ) Due Today a • Dynamic Rules • FIFO* • Cr* • LS* • LSPRO* 1919

  21. 19 Prioritisation and Sequencing – 3 m n Time Available (T ) Due Today a • Informal Rules • Least Loaded Next W/C • Easiest Next Set-up* • Biggest Bonus • Who Shouts Loudest • Undefined 1920

  22. 19 Prioritisation and Sequencing – 4 Priority List A B C D E F G H I J Selection Window This Approach is a Compromise Between Set-Up Time and Manufacturing in a sequence related to Customer Requirements 1921

  23. 19 Shop Floor Feedback • Completions • Time Required • Process Data • Labour Productivity M/C Efficiency • M/C Breakdowns • Scrap • Rework • Defect Analysis <102394> Transducer Smart Tag Controller Hand Held Computer Application Direct • Remote Entry • Shop Floor Terminals • Data Collection Software Interface 1922

  24. 19 Short Interval Scheduling (SIS) Business Planning Sales and Operations Planning Master Production Scheduling Upload Download Interface Material Requirements Planning Capacity Requirements Planning SIS System • Hybrid Approach • Simulation • What-if Analysis • Operational • Rough Cut Capacity Planning • Cannot Cope with a Heavily Overloaded Situation No Realistic Yes Shop Floor Control Purchasing 1923

  25. 19 Rough Cut Capacity Planning – 1 Objective: to Check that the MPS is Valid MPS Product Load Profile Resources RCCP Load Per Unit • Production Line • Critical Work Centres • Labour • Key Supplier Capacity • Testing Resource Load Profile Time Before Due Date Load Capacity Time 1924

  26. 19 Rough Cut Capacity Planning – 2 • Objectives • Checks MPS Validity • Shows Impact of Product Mix • Allows "What-if" Analysis • Limitations • Only Consider Key Resources • Ignores Inventory of Components • Does not Monitor Work Order Execution 1925

  27. 19 RCCP vs CRP RCCP CRP Estimated Load on critical Detailed evaluation of load Definition resources based on MPS based at work centre level Use of MPS and product Calculation based on all Method load profiles works orders As required Following each MRP run - Frequency typically once a week 1. Pre-MRP evaluation of MPS 1. Post-MRP analysis Objective 2. Operational planning 2. Determining bottlenecks Detailed Aggregate Precision MPS and product load profiles Works orders, work centres, Data routings and works order status Fast Typically longer than MRP Speed Virtually all users of formal A minority of users Use manufacturing management Systems 1926

  28. 19 Disadvantages of CRP • Data Hungry • Need for Feedback • Timing of Information 1927

  29. 19 OPT Background • Doubts Over MRPII • Developed by Dr EM Goldratt in the 1970s. • OPT has Two Elements • Philosophical • Finite Scheduling Algorithm 1928

  30. Throughput Net Profit Inventory ROCE Operating Expense Cash Flow 19 OPT Principles "The Goal" - To Make Money OPT Emphasises the Importance of Bottlenecks. A Bottleneck is any Resource where Capacity is less than Load 1929

  31. 19 Ten Rules of OPT 1. Balance flow, not capacity. 2. The level of utilisation of a non-bottleneck is determined not by its own potential, but by some other constraint in the system. 3. Utilisation and activation of a resource are not necessarily the same thing. 4. An hour lost at a bottleneck is an hour lost for the total system. 5. An hour saved at a non-bottleneck is a mirage. 6. Bottlenecks govern both throughput and inventory. 7. The transfer batch may not, and many times should not, be equal to the process batch. 8. The process batch should be variable, not fixed. 9. Capacity and priority should be considered simultaneously, not sequentially. 10. The sum of local optima is not equal to the optimum of the whole system. 1930

  32. Process Batch Larger than the Transfer Batch Op 10 Op 20 Op 30 Op 40 19 Process and Transfer Batches - 1 Standard Case – Process Batch and Transfer Batch the Same Size Operation 10 Operation 20 Operation 30 Operation 40 1931

  33. 19 OPT Mechanics Routing Critical OPT Resource OPT Network Schedule Initial SPLIT SERVE BUILDNET Analysis Non-Critical SERVE SERVE Resource Network Schedule BOM 1934

  34. 19 OPT Features • Lot Sizes • Variable Transfer Batch • Variable Process Batch • Set-up • Tabular Approach to Dependencies • Reports • Utilisation • Stockman • Despatch • Daily Foreman • Raw Material Requirements 1935

  35. Non Critical Resource Network Critical Resource Network 19 OPT Network Raw Material Components Finished Goods Inventory Assemblies Critical Capacity Restraint 1936

  36. 19 Drum-Buffer-Rope Analogy Buffer Drum Material Launched into System Rope Bottleneck Resource • Drum. The Scheduling Rhythm. • Rope. "Pulling" Material into the System. • Buffers. Providing a Time Safety Margin. 1937

  37. 19 Limitations of FCS • Complex • Expensive • Stochastic Process and Set-up Times • Set-up Time Dependency • Automatic Rescheduling of a Backlog Cannot Act as a Substitute for Poor Management 1938

  38. 19 FCS - Summary • FCS - Relatively Old Approach • Made Popular By OPT • Simulation of the Manufacturing System • Can be Employed in Several Forms • Full Scheduling System • Short Interval Scheduling • Enhanced RCCP • Will be Used More Widely in the Future (APS) 1939

  39. 19 AlterCo Case Study - Overview Location East Lancashire Size 315 Employees Turnover £15M Products Alternators Production 6000 units/wk Spares Production None Business Type Make to stock and order Variety 100 stock types plus specials 1940

  40. 19 AlterCo - History • Problems in the 70's • Overdues • Excessive Overtime • Excessive Inventory • Shortages • Computer System Lost Credibility • Serious Cash Flow Problems 1941

  41. AlterCo – Bill of Material 19 1942

  42. 19 AlterCo – Material Flow Shaft Line Winding Line Raw Finished Component Material Assembly Goods Stores Stores Stores End Cover Line Other Parts Despatch 1943

  43. 19 AlterCo – The Initial Response The Companies Position was Becoming Serious • Increase Batch Size to Improve Efficiency • Sequence Work to Minimise Set-ups • Increase Lead Times • Increase Capacity in All Areas 1944

  44. 19 AlterCo - The Exercise • Planned to Take Similar Actions • Set-up a Project Team • Their Objective - Short Term Improvement • Your Task • What was the Project Team's Assessment? • What Action Did they Take? 1945

  45. 19 AlterCo – The Real Problems (1) • Winding was a Bottleneck • Surprisingly, Other Sections Also Had Overdues • Other Sections Were Making the Wrong Types • Manufacture in the Wrong Sequence • Unmatched Inventory 1946

  46. 19 AlterCo – The Real Problems (2) 1 Sequenced Work Increased Overdues Increase Batches 2 Increased Overtime Increased Capacity Increased Stocks 3 Increased Lead Time Increased WIP 1947

  47. Customer Orders Other Manufacturing Sections 19 AlterCo – The Short Term Solution MRP Winding 1948

  48. 19 AlterCo – The Results (1) • Output of Finished Goods Up • Most Overdue Jobs Completed First • Overtime Eliminated Except for Winding • Reduced Purchasing in Short Term • WIP/Lead Times Reduced Efficiency Reduced!! 1949

  49. 19 AlterCo – The Results (2) Measure of Performance January April Shaft Stocks 35000 25000 Shaft WIP 15000 6400 Shaft Lead Time 2.5 Wks 1 Wk End Cover Stocks 40000 32000 Shaft Output 7800 5010 Overall Output 6000 8700 Overall Overdues 21000 13000 But the Project Team Advised Caution 1950

  50. 19 AlterCo – The Need for Caution • Stocks Would Eventually be Consumed • Non-bottlenecks Would Need to Increase Output • Only Winding had Any Forward Vision 1951

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