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Lecture 20 Production Activity Control (Revision)

Lecture 20 Production Activity Control (Revision). Books Introduction to Materials Management, Sixth Edition, J. R. Tony Arnold, P.E., CFPIM, CIRM, Fleming College, Emeritus, Stephen N. Chapman, Ph.D., CFPIM, North Carolina State University, Lloyd M. Clive, P.E., CFPIM, Fleming College

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Lecture 20 Production Activity Control (Revision)

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  1. Lecture 20Production Activity Control (Revision) Books Introduction to Materials Management, Sixth Edition, J. R. Tony Arnold, P.E., CFPIM, CIRM, Fleming College, Emeritus, Stephen N. Chapman, Ph.D., CFPIM, North Carolina State University, Lloyd M. Clive, P.E., CFPIM, Fleming College Operations Management for Competitive Advantage, 11th Edition, by Chase, Jacobs, and Aquilano, 2005, N.Y.: McGraw-Hill/Irwin. Operations Management, 11/E, Jay Heizer, Texas Lutheran University, Barry Render, Graduate School of Business, Rollins College, Prentice Hall

  2. Objectives • Production activity control • Gantt chart • Critical ratio scheduling • Finite loading • Scheduling • Assignment method • Sequencing • Slack • Johnson's Rule • Monitoring • Advance planning and scheduling • Scheduling procedure • Employee Scheduling

  3. Production Activity Control • PAC in the MPC System • Shop Floor Control • Vendor Scheduling • Production Activity Control Techniques • Basic Data • Gantt Charts • Priority Scheduling • Finite Loading • Process Design Impact on Scheduling • Batch Manufacturing – Work Orders • Repetitive Manufacturing – JIT

  4. Production Activity Control in the MPC System

  5. Basic Data

  6. Routing Data and Operation Setback Chart

  7. Gantt Charts The incoming orders at Tom's Sailboard follow different routes through the shop but all orders must stop at each of the three work centers in the plant. The table below shows all tasks for four jobs that arrive over 5 days and need to be scheduled at the company. It is currently November 10 and Tom works a seven-day week. _____________________________________________________ Arrival Job/WC Processing time (days) Order date routing WC 1WC 2WC 3 (B)iff Nov. 10 1-3-2 1 3 1 (G)riffin Nov. 10 2-3-1 2 2 2 (H)erbie Nov. 12 3-2-1 3 1 2 (K)errie Nov. 14 2-1-3 1 3 1 Assume that the new material for all orders is in stock and that a first-come/first-served sequencing rule is used at all work centers. All three work centers are idle as work begins on orders B and G on November 10.

  8. Tom’s Sailboard • Construct a Gantt chart depicting the processing and idle times for the three work centers for these four jobs. Arrival Job/WC Processing time (days) Order date routing WC 1WC 2WC 3 (B)iffNov. 10 1-3-2131 (G)riffin Nov. 10 2-3-1 2 2 2 (H)erbie Nov. 12 3-2-1 3 1 2 (K)errie Nov. 14 2-1-3 1 3 1

  9. Tom’s Sailboard • How many days does each job wait in queue for processing at work center 2? The determination of how long jobs wait at work center 2 is as follows: B and G are processed immediately at work center 2, order K must wait 1 day (11/14) and order H waits 4 days (11/12, 11/13 at WC3) and (11/16 and 11/17 at WC2).

  10. Priority Sequencing Rules • First Come, First Served • Shortest Operation Next • Earliest Due Date • Order Slack: (Time Remaining until Due Date – Sum of Remaining Setup and Run Time) • Slack per Operation • Critical Ratio: (Due Date-Now)/(Lead Time Remaining) ________________________________________ Lead Time Remaining includes setup, run, move and queue time for all remaining operations.

  11. Knox Machine • The jobs below are waiting to be processed at the P&W Grinder at the Knox Machine Company. (There are no other jobs and the machine is empty.) __________________________ Machine processing Date job arrived Job due Job time (in days)*__at this machine date__ A 4 6-23 8-15 B 1 6-24 9-10 C 5 7-01 8-01 D 2 6-19 8-17 *Note: This is the final operation for each of these jobs. ___________________________________________________________

  12. Knox Machine: Solution • The production manager has heard about three dispatching rules: the Shortest Operation Next Rule, the First-Come/First-Served Rule, and the Earliest Due Date Rule. In what sequence would these jobs be processed at the P&W grinder if each rule was applied? • The shortest operation next rule: B-D-A-C • The first-come, first-served rule: D-A-B-C • The earliest due date rule: C-A-D-B Machine processing Date job arrived Job due Job time (in days)*__at this machine date__ A 4 6-23 8-15 B 1 6-24 9-10 C 5 7-01 8-01 D 2 6-19 8-17 *Note: This is the final operation for each of these jobs.

  13. Knox Machine: Solution • If it's now the morning of July 10 and the Shortest Operation Next Rule is used, when would each of the four jobs start and be completed on the P&W grinder? (Express your schedule in terms of the calendar dates involved, assuming that there are 7 working days each week.) P & W Grinder

  14. Critical Ratio Scheduling Eight weeks remain for constructing the a 50­foot yacht. Assume that each week consists of 5 work days, for a total lead time of 40 days. The work required to complete the yacht comprises 10 operations, 4 days for each.

  15. Yacht Project Example • On Tuesday morning of week 3, 3 of the 10 operations had been completed and the yacht was waiting for the fourth operation. What's the critical ratio priority?

  16. Yacht Project Example • What's the critical ratio priority if only 2 of the 10 operations are completed by Tuesday morning of week 3?

  17. Finite Loading

  18. The Bundy Company The Bundy Company produces for three products (A, K, and P). Each order goes through the same three machine centers, but not necessarily in the same sequence. Each order must be finished at a machine center before another can be started. Orders cannot be split. The shop works a single eight-hour shift five days per week. Assume that the time to move between machines is negligible. each machine center is operated eight hours per day. All three machines are currently available for scheduling, and no further orders will arrive.

  19. The Bundy Company Processing time Machine at machine center center ___(in days)____ Order Orderrouting123due date A 3-1-2 1 3 2 14 K 2-3-1 3 1 3 12 P 3-2-1 2 3 4 10 Note: Order due dates are fixed based on the shop calendar. It is now 8:00 A.M. Monday (day 1), Monday of next week is day 6, etc.

  20. The Bundy Company Using the horizontal loading procedure with earliest-due-date priority sequencing rule, prepare a Gantt chart showing the production schedule for the three orders above.

  21. The Bundy Company Using the vertical loading procedure and the shortest-operation-next priority sequencing rule, prepare a Gantt chart showing the production schedule for the three orders above.

  22. Scheduling

  23. What is Scheduling? • Last stage of planning before production occurs • Specifies when labor, equipment, and facilities are needed to produce a product or provide a service

  24. Scheduled Operations • Process Industry • Linear programming • EOQ with non-instantaneous replenishment • Mass Production • Assembly line balancing • Project • Project -scheduling techniques (PERT, CPM) • Batch Production • Aggregate planning • Master scheduling • Material requirements planning (MRP) • Capacity requirements planning (CRP)

  25. Objectives in Scheduling • Meet customer due dates • Minimize job lateness • Minimize response time • Minimize completion time • Minimize time in the system • Minimize overtime • Maximize machine or labor utilization • Minimize idle time • Minimize work-in-process inventory

  26. Shop Floor Control (SFC) • Schedule and monitor day-to-day job shop production • Also called production control and production activity control (PAC) • Performed by production control department • Loading - check availability of material, machines, and labor • Sequencing - release work orders to shop and issue dispatch lists for individual machines • Monitoring - maintain progress reports on each job until it is complete

  27. Loading • Process of assigning work to limited resources • Perform work with most efficient resources • Use assignment method of linear programming to determine allocation

  28. Assignment Method • Perform row reductions • subtract minimum value in each row from all other row values • Perform column reductions • subtract minimum value in each column from all other column values • Cross out all zeros in matrix • use minimum number of horizontal and vertical lines • If number of lines equals number of rows in matrix, then optimum solution has been found. Make assignments where zeros appear • Else modify matrix: • subtract minimum uncrossed value from all uncrossed values • add it to all cells where two lines intersect • other values in matrix remain unchanged • Repeat steps 3 and 4 until optimum solution is reached

  29. Assignment Method Initial PROJECT Matrix 1 2 3 4 Bryan 10 5 6 10 Kari 6 2 4 6 Noah 7 6 5 6 Chris 9 5 4 10 Row reduction Column reduction Cover all zeros 5 0 1 5 3 0 1 4 3 0 1 4 4 0 2 4 2 0 2 3 2 0 2 3 2 1 0 1 0 1 0 0 0 1 0 0 5 1 0 6 3 1 0 5 3 1 0 5 Number lines  number of rows so modify matrix

  30. Assignment Method Modify matrix Cover all zeros 1 0 1 2 1 0 1 2 0 0 2 1 0 0 2 1 0 3 2 0 0 3 2 0 1 1 0 3 1 1 0 3 Number of lines = number of rows so at optimal solution PROJECT PROJECT 1 2 3 4 Bryan 10 5 6 10 Kari 6 2 4 6 Noah 7 6 5 6 Chris 9 5 4 10 1 2 3 4 Bryan 1 0 1 2 Kari 0 0 2 1 Noah 0 3 2 0 Chris 1 1 0 3 Project Cost = (5 + 6 + 4 + 6) X $100 = $2,100

  31. Assignment Method - Setup Solution goes hereOnly 1 leader canbe assigned to each project Click “Solve” for solution Sum of all rows and columns = 1

  32. Assignment Method - Solution Assignments indicated by 1 Cost of solution

  33. Sequencing • Prioritize jobs assigned to a resource • If no order specified use first-come first-served (FCFS) • Other Sequencing Rules • FCFS - first-come, first-served • LCFS - last come, first served • DDATE - earliest due date • CUSTPR - highest customer priority • SETUP - similar required setups • SLACK - smallest slack • CR - smallest critical ratio • SPT - shortest processing time • LPT - longest processing time

  34. Minimum Slack & Smallest Critical Ratio • SLACK considers both work and time remaining • CR recalculates sequence as processing continues and arranges information in ratio form SLACK = (due date – today’s date) – (processing time) time remaining due date - today’s date work remaining remaining processing time CR = = If CR > 1, job ahead of schedule If CR < 1, job behind schedule If CR = 1, job on schedule

  35. Sequencing Jobs Through One Process • Flow time (completion time) • Time for a job to flow through system • Makespan • Time for a group of jobs to be completed • Tardiness • Difference between a late job’s due date and its completion time

  36. Simple Sequencing Rules PROCESSING DUE JOB TIME DATE A 5 10 B 10 15 C 2 5 D 8 12 E 6 8

  37. Simple Sequencing Rules: FCFS FCFS START PROCESSING COMPLETION DUE SEQUENCE TIME TIME TIME DATE TARDINESS A 0 5 5 10 0 B 5 10 15 15 0 C 15 2 17 5 12 D 17 8 25 12 13 E 25 6 31 8 23 Total 93 48 Average 93/5 = 18.60 48/5 = 9.6

  38. Simple Sequencing Rules: DDATE DDATE START PROCESSING COMPLETION DUE SEQUENCE TIME TIME TIME DATE TARDINESS C 0 2 2 5 0 E 2 6 8 8 0 A 8 5 13 10 3 D 13 8 21 12 9 B 21 10 31 15 16 Total75 28 Average 75/5 = 15.00 28/5 = 5.6

  39. Simple SequencingRules: SLACK A (10-0) – 5 = 5 B (15-0) – 10 = 5 C (5-0) – 2 = 3 D (12-0) – 8 = 4 E (8-0) – 6 = 2 SLACK START PROCESSING COMPLETION DUE SEQUENCE TIME TIMETIME DATE TARDINESS E 0 6 6 8 0 C 6 2 8 5 3 D 8 8 16 12 4 A 16 5 21 10 11 B 21 10 31 15 16 Total 82 34 Average 82/5 = 16.40 34/5 = 6.8

  40. Simple Sequencing Rules: SPT SPT START PROCESSING COMPLETION DUE SEQUENCE TIME TIME TIME DATE TARDINESS C 0 2 2 5 0 A 2 5 7 10 0 E 7 6 13 8 5 D 13 8 21 12 9 B 21 10 31 15 16 Total 74 30 Average 74/5 = 14.80 30/5 = 6

  41. Simple Sequencing Rules: Summary AVERAGE AVERAGE NO. OF MAXIMUM RULE COMPLETION TIME TARDINESS JOBS TARDY TARDINESS FCFS 18.60 9.6 3 23 DDATE 15.00 5.6 3 16 SLACK 16.40 6.8 4 16 SPT 14.80 6.0 3 16 Best values

  42. Sequencing Jobs Through Two Serial Process Johnson’s Rule • List time required to process each job at each process. Set up a one-dimensional matrix to represent desired sequence with # of slots equal to # of jobs. • Select smallest processing time at either process. If that time is on process 1, put the job as near to beginning of sequence as possible. • If smallest time occurs on process 2, put the job as near to the end of the sequence as possible. • Remove job from list. • Repeat steps 2-4 until all slots in matrix are filled and all jobs are sequenced.

  43. SequencingWithExcel

  44. Johnson’s Rule JOB PROCESS 1 PROCESS 2 A 6 8 B 11 6 C 7 3 D 9 7 E 5 10 B A E C D

  45. Johnson’s Rule E A D B C Process 1 (sanding) E A D B C 5 11 20 31 38 Idle time Process 2 (painting) E A D B C 5 15 23 30 37 41 Completion time = 41 Idle time = 5+1+1+3=10

  46. Excel for Johnson’s Rule User inputs processingtimes and sequence Excel calculatescompletion timesand makespan When the set ofjobs is completed

  47. Guidelines for Selecting a Sequencing Rule • SPT most useful when shop is highly congested • Use SLACK for periods of normal activity • Use DDATE when only small tardiness values can be tolerated • Use LPT if subcontracting is anticipated • Use FCFS when operating at low-capacity levels • Do not use SPT to sequence jobs that have to be assembled with other jobs at a later date

  48. Monitoring • Work package • Shop paperwork that travels with a job • Gantt Chart • Shows both planned and completed activities against a time scale • Input/Output Control • Monitors the input and output from each work center

  49. Gantt Chart Job 32B Behind schedule 3 Job 23C Ahead of schedule 2 Facility Job 11C Job 12A On schedule 1 1 2 3 4 5 6 8 9 11 12 Days 10 Today’s Date Key: Planned activity Completed activity

  50. Input/Output Control PERIOD 1 2 3 4 TOTAL Planned input 65 65 70 70 270 Actual input 0 Deviation 0 Planned output 75 75 75 75 300 Actual output 0 Deviation 0 Backlog 30 20 10 5 0

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