1. Lecture 14 Production Activity Control (Continued) 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 Sequencing Slack Johnson's Rule Monitoring Advance planning and scheduling TOC Scheduling procedure Employee Scheduling

3. 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

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

5. 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

6. Simple Sequencing Rules PROCESSINGDUE JOBTIMEDATE A510 B1015 C25 D812 E68

7. Simple Sequencing Rules: FCFS A055100 B51015150 C15217512 D178251213 E25631823 Total 9348 Average 93/5 = 18.60 48/5 = 9.6 FCFSSTARTPROCESSINGCOMPLETIONDUE SEQUENCETIMETIMETIMEDATETARDINESS

8. Simple Sequencing Rules: DDATE C02250 E26880 A8513103 D13821129 B2110311516 Total7528 Average75/5 = 15.00 28/5 = 5.6 DDATESTARTPROCESSINGCOMPLETIONDUE SEQUENCETIMETIMETIMEDATETARDINESS

9. Simple Sequencing Rules: 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 E06680 C62853 D8816124 A165211011 B2110311516 Total8234 Average82/5 = 16.40 34/5 = 6.8 SLACKSTARTPROCESSINGCOMPLETIONDUE SEQUENCETIMETIMETIMEDATETARDINESS

10. Simple Sequencing Rules: SPT C02250 A257100 E761385 D13821129 B2110311516 Total7430 Average74/5 = 14.80 30/5 = 6 SPTSTARTPROCESSINGCOMPLETIONDUE SEQUENCETIMETIMETIMEDATETARDINESS

11. Simple Sequencing Rules: Summary FCFS18.609.6323 DDATE15.005.6316 SLACK16.406.8416 SPT14.806.0316 AVERAGEAVERAGENO. OFMAXIMUM RULECOMPLETION TIMETARDINESSJOBS TARDYTARDINESS Best values

12. Sequencing Jobs Through Two Serial Process Johnson’s Rule 1.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. 2.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. 3.If smallest time occurs on process 2, put the job as near to the end of the sequence as possible. 4.Remove job from list. 5.Repeat steps 2-4 until all slots in matrix are filled and all jobs are sequenced.

13. Sequencing With Excel

14. Johnson’s Rule JOBPROCESS 1PROCESS 2 A68 B116 C73 D97 E510 CE A B D

15. Johnson’s Rule ABCDE EADBC Process 1 (sanding) 511203138 EADBC Process 2 (painting) 51523303741 Idle time Completion time = 41 Idle time = 5+1+1+3=10

16. Excel for Johnson’s Rule User inputs processing times and sequence Excel calculates completion times and makespan When the set of jobs is completed

17. 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

18. 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

19. Gantt Chart 12345689 10 1112Days 1 2 3 Today’s Date Job 32B Job 23C Job 11CJob 12A Facility Key: Planned activity Completed activity Behind schedule Ahead of schedule On schedule

20. Input/Output Control Planned input65657070270 Actual input0 Deviation0 Planned output75757575300 Actual output0 Deviation0 Backlog30 PERIOD1234TOTAL 20 10 5 0

21. Input/Output Control Planned input65657070270 Actual input60606565250 Deviation-5-5-5-5-20 Planned output75757575300 Actual output75756565280 Deviation-0-0-10-10-20 Backlog3015000 PERIOD1234TOTAL

22. Excel for Input/Output Control User inputs planned and actual values Excel calculates deviations and backlog

23. Advanced Planning and Scheduling Systems Infinite scheduling - assumes infinite capacity –Loads without regard to capacity –Then levels the load and sequences jobs Finite scheduling - assumes finite (limited) capacity –Sequences jobs as part of the loading decision –Resources are never loaded beyond capacity

24. Advanced Planning and Scheduling Systems Advanced planning and scheduling (APS) –Add-ins to ERP systems –Constraint-based programming (CBP) identifies a solution space and evaluates alternatives –Genetic algorithms based on natural selection properties of genetics –Manufacturing execution system (MES) monitors status, usage, availability, quality

25. Advanced Planning and Scheduling

26. Theory of Constraints Not all resources are used evenly Finite scheduling approach Concentrate on the” bottleneck” resource Synchronize flow through the bottleneck Use process and transfer batch sizes to move product through facility

27. Drum-Buffer-Rope Drum –Bottleneck, beating to set the pace of production for the rest of the system Buffer –Inventory placed in front of the bottleneck to ensure it is always kept busy –Determines output or throughput of the system Rope –Communication signal; tells processes upstream when they should begin production

28. TOC Scheduling Procedure Identify bottleneck Schedule job first whose lead time to bottleneck is less than or equal to bottleneck processing time Forward schedule bottleneck machine Backward schedule other machines to sustain bottleneck schedule Transfer in batch sizes smaller than process batch size

29. Synchronous Manufacturing B A C D B1 1 5 B2 2 3 B3 1 7 C1 3 2 C2 1 10 C3 2 15 D1 3 10 D2 2 8 D3 3 5 Item i Key: i Ij k l Operation j of item i performed at machine center k takes l minutes to process

30. Synchronous Manufacturing Demand = 100 A’s Machine setup time = 60 minutes MACHINE 1MACHINE 2MACHINE 3 B15B23C12 B37C315D35 C210D28D110 Sum2226*17 * Bottleneck

31. Synchronous Manufacturing Machine 1 Machine 3 Setup Completion time 10022322 122732 020012601940 2737 C2B1B3 C3B2D2 C1D1D3Idle Setup 1562 15121872 Setup Machine 2 Idle 2

32. Employee Scheduling Labor is very flexible resource Scheduling workforce is complicated, repetitive task Assignment method can be used Heuristics are commonly used

33. Employee Scheduling Heuristic 1.Let N = no. of workers available D i = demand for workers on day i X = day working O = day off 2.Assign the first N - D 1 workers day 1 off. Assign the next N - D 2 workers day 2 off. Continue in a similar manner until all days are have been scheduled 3.If number of workdays for full time employee < 5, assign remaining workdays so consecutive days off are possible 4.Assign any remaining work to part-time employees 5.If consecutive days off are desired, consider switching schedules among days with the same demand requirements

34. Employee Scheduling DAY OF WEEKMTWTHFSASU MIN NO. OF WORKERS REQUIRED3343453 Taylor Smith Simpson Allen Dickerson

35. Employee Scheduling DAY OF WEEKMTWTHFSASU MIN NO. OF WORKERS REQUIRED3343453 TaylorOXXOXXX SmithOXXOXXX SimpsonXOXXOXX AllenXOXXXXO DickersonXXOXXXO Completed schedule satisfies requirements but has no consecutive days off

36. DAY OF WEEKMTWTHFSASU MIN NO. OF WORKERS REQUIRED3343453 TaylorOOXXXXX SmithOOXXXXX SimpsonXXOOXXX AllenXXXOXXO DickersonXXXXOXO Revised schedule satisfies requirements with consecutive days off for most employees Employee Scheduling

37. Automated Scheduling Systems Staff Scheduling –Assign workers to standardize shift patterns Schedule Bidding –Workers bid for certain shift positions or schedules Schedule Optimization –Creates demand-driven forecast of labor needs –Assigns workers to variable schedules –Uses mathematical programming and artificial intelligence techniques

38. End of Lecture 14