1. Scheduling Çizelgeleme
Chapter 16
Scheduling Çizelgeleme
Operations Management - 5th Edition
Roberta Russell & Bernard W. Taylor, III
Beni Asllani University of Tennessee at Chattanooga
Copyright 2006 John Wiley & Sons, Inc.

2. Lecture Outline Objectives in Scheduling Loading Sequencing Monitoring
Advanced Planning and Scheduling Systems
Theory of Constraints
Employee Scheduling
Copyright 2006 John Wiley & Sons, Inc.

3. What is Scheduling? Çizelgeleme Nedir?)
Last stage of planning before production occurs (üretimin gerçekleşmesinden önceki son aşama
Specifies when labor, equipment, facilities are needed to produce a product or provide a service (bir ürün ya da hizmet sağlamak için işgücü, donanım, tesislere ne zaman ihtiyaç duyulacağını belirler)
Copyright 2006 John Wiley & Sons, Inc.

4. Scheduled Operations Process Industry Mass Production Project
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)
Copyright 2006 John Wiley & Sons, Inc.

5. Objectives in Scheduling Çizelgelemenin Amaçları
Meet customer due dates (müşteriye teslim tarihlerinin karşılanması)
Minimize job lateness (gecikmelerin minimize edilmesi)
Minimize response time (tepki sürelerinin minimize edilmesi)
Minimize completion time (tamamlanma sürelerinin minimize edilmesi)
Minimize time in the system (sistemde geçirilen sürenin minimize edilmesi
Minimize overtime (fazla mesainin minimize edilmesi)
Maximize machine or labor utilization (Makine ve işgücü kullanım oranlarının maksimize edilmesi)
Minimize idle time (boş zamanın minimize edilmesi)
Minimize work-in-process inventory (işlenmekte olan parça stokunun minimize edilmesi)
Copyright 2006 John Wiley & Sons, Inc.

6. Shop Floor Control (Atöyle Denetimi
Loading (İş yükleme)
Check availability of material, machines and labor Malzeme, makine ve işgücünün mevcudiyetinin kontrol edilmesi
Sequencing (İş sıralama)
Release work orders to shop and issue dispatch lists for individual machines Atölyeye, bireysel makineler için iş emirlerinin gönderilmesi
Monitoring (izleme)
Maintain progress reports on each job until it is complete Her iş(sipariş) tamamlanıncaya kadar ilerleme raporlarının hazırlanması
Copyright 2006 John Wiley & Sons, Inc.

7. Loading İş yükleme
Process of assigning work to limited resources Sınırlı kaynaklara işlerin tahsis edilmesi süreci
Perform work on most efficient resources Et etkin kaynaklar üzerinde işin yapılması
Use assignment method of linear programming to determine allocation Tahsis için DP’nin tahsis yönteminin kullanılması
Copyright 2006 John Wiley & Sons, Inc.

8. Assignment Method Perform row reductions Perform column 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 through 5 until optimum solution is reached
Copyright 2006 John Wiley & Sons, Inc.

9. Assignment Method: Example
Initial PROJECT
Matrix
Bryan
Kari
Noah
Chris
Row reduction Column reduction Cover all zeros
Number lines  number of rows so modify matrix
Copyright 2006 John Wiley & Sons, Inc. 12

10. Assignment Method: Example (cont.)
Modify matrix Cover all zeros
Number of lines = number of rows so at optimal solution
Bryan
Kari
Noah
Chris
PROJECT
Bryan
Kari
Noah
Chris
Project Cost = ( ) X $100 = $2,100
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11. Sequencing Prioritize jobs assigned to a resource
If no order specified use first-come first-served (FCFS)
Many other sequencing rules exist
Each attempts to achieve to an objective
Copyright 2006 John Wiley & Sons, Inc.

12. Sequencing Rules Sıralama Kuralları)
FCFS - first-come, first-served (İl gelene ilk hizmet)
LCFS - last come, first served (Son gelene ilk hizmet)
DDATE - earliest due date (en erken teslim tarihi)
CUSTPR - highest customer priority (en yüksek müşteri önceliği)
SETUP - similar required setups (benzer makine hazırlık gerektiren)
SLACK - smallest slack (boşluğu en küçük olan)
CR - critical ratio (kritik oran
SPT - shortest processing time (en düşük işleme süresi)
LPT - longest processing time (en uzun işleme süresi)
Copyright 2006 John Wiley & Sons, Inc.

13. Critical Ratio Rule CR considers both time and work remaining Hem
süreyi hem de kalan süreyi ele alır
CR = =
If CR > 1, job ahead of schedule (iş, planın ilerisindedir)
If CR < 1, job behind schedule (iş, planın gerisindedir)
If CR = 1, job on schedule (iş, planlandığı gibi gitmektedir)
time remaining kalan süre) due date - today’s date
work remaining(kalan iş) remaining processing time
Copyright 2006 John Wiley & Sons, Inc.

14. Sequencing Jobs Through One Process
Flowtime (completion time) Akış süresi (tamamlanma zamanı)
Time for a job to flow through the system (bir işin sistemde akış süresi)
Makespan (üretim süresi
Time for a group of jobs to be completed (bir grup işin tamamlanma süresi)
Tardiness (Gecikme)
Difference between a late job’s due date and its completion time (işin teslim tarihi ile tamamlanma tarihi arasındaki fark)
Copyright 2006 John Wiley & Sons, Inc.

15. Simple Sequencing Rules
PROCESSING DUE
JOB TIME DATE
A 5 10
B 10 15
C 2 5
D 8 12
E 6 8
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16. Simple Sequencing Rules: FCFSA B C D E
FCFS START PROCESSING COMPLETION DUE
SEQUENCE TIME TIME TIME DATE TARDINESS
Copyright 2006 John Wiley & Sons, Inc.

17. Simple Sequencing Rules: DDATEB
DDATE START PROCESSING COMPLETION DUE
SEQUENCE TIME TIME TIME DATE TARDINESS
Copyright 2006 John Wiley & Sons, Inc.

18. Simple Sequencing Rules: SLACK
B (15-0) - 10 = 5
C (5-0) – 2 = 3
D (12-0) – 8 = 4
E (8-0) – 6 = 2
Simple Sequencing Rules: SLACK E C D A B
SLACK START PROCESSING COMPLETION DUE
SEQUENCE TIME TIME TIME DATE TARDINESS
Copyright 2006 John Wiley & Sons, Inc.

19. Simple Sequencing Rules: CR
A (10)/5 = 2.00
B (15)/10 = 1.50
C (5)/2 = 2.50
D (12)/8 = 1.50
E (8)/6 = 1.33
Simple Sequencing Rules: CR E D B A C
CR START PROCESSING COMPLETION DUE
SEQUENCE TIME TIME TIME DATE TARDINESS
Copyright 2006 John Wiley & Sons, Inc.

20. Simple Sequencing Rules: SPTA E D B
SPT START PROCESSING COMPLETION DUE
SEQUENCE TIME TIME TIME DATE TARDINESS
Copyright 2006 John Wiley & Sons, Inc.

21. Simple Sequencing Rules: Summary
FCFS
DDATE
SLACK CR
SPT
AVERAGE AVERAGE NO. OF MAXIMUM
RULE COMPLETION TIME TARDINESS JOBS TARDY TARDINESS
Copyright 2006 John Wiley & Sons, Inc.

22. Sequencing Jobs Through Two Serial Process
Johnson’s Rule
List time required to process each job at each machine. Set up a one-dimensional matrix to represent desired sequence with # of slots equal to # of jobs.
Select smallest processing time at either machine. If that time is on machine 1, put the job as near to beginning of sequence as possible.
If smallest time occurs on machine 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.
Copyright 2006 John Wiley & Sons, Inc.

23. Johnson’s Rule A B C D E JOB PROCESS 1 PROCESS 2 A 6 8 B 11 6 C 7 3
Copyright 2006 John Wiley & Sons, Inc.

24. Johnson’s Rule (cont.) E A D B C Completion time = 41
Process 1
(sanding) 5 11 20 31 38
Process 2
(painting) 15 23 30 37 41
Idle time
Completion time = 41
Idle time = =10
Copyright 2006 John Wiley & Sons, Inc.

25. 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
Copyright 2006 John Wiley & Sons, Inc.

26. Monitoring Work package Gantt Chart Input/Output Control
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
Copyright 2006 John Wiley & Sons, Inc.

27. Gantt Chart 1 2 3 4 5 6 8 9 10 11 12 Days Today’s Date Job 32B Job 23C
Job 12A
Facility
Key:
Planned activity
Completed activity
Behind schedule
Ahead of schedule
On schedule
Copyright 2006 John Wiley & Sons, Inc.

28. Input/Output Control Input/Output Report PERIOD 1 2 3 4 TOTAL
Planned input
Actual input
Deviation
Planned output
Actual output
Backlog 30
PERIOD TOTAL
Copyright 2006 John Wiley & Sons, Inc.

29. Input/Output Control (cont.)
Input/Output Report
Planned input
Actual input
Deviation
Planned output
Actual output
Deviation
Backlog
PERIOD TOTAL
Copyright 2006 John Wiley & Sons, Inc.

30. Advanced Planning and Scheduling Systems
Infinite - assumes infinite capacity
Loads without regard to capacity
Then levels the load and sequences jobs
Finite - assumes finite (limited) capacity
Sequences jobs as part of the loading decision
Resources are never loaded beyond capacity
Copyright 2006 John Wiley & Sons, Inc.

31. Advanced Planning and Scheduling Systems (cont.)
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
Copyright 2006 John Wiley & Sons, Inc.

32. Theory of Constraints Not all resources are used evenly
Concentrate on the” bottleneck” resource
Synchronize flow through the bottleneck
Use process and transfer batch sizes to move product through facility
Copyright 2006 John Wiley & Sons, Inc.

33. Drum-Buffer-Rope Drum Buffer Rope
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
Copyright 2006 John Wiley & Sons, Inc.

34. TOC Scheduling Procedure
Identify bottleneck
Schedule job first whose lead time to the bottleneck is less than or equal bottleneck processing time
Forward schedule the bottleneck machine
Backward schedule the other machines to sustain the bottleneck schedule
Transfer in batch sizes smaller than the process batch size
Copyright 2006 John Wiley & Sons, Inc.

35. Synchronous ManufacturingB A C D B B B C C C D D D
Operation j of item i performed at
machine center k takes l minutes
to process
Item i
Key: i
ij k l
Synchronous Manufacturing
Copyright 2006 John Wiley & Sons, Inc.

36. Synchronous Manufacturing (cont.)
Demand = 100 A’s
Machine setup time = 60 minutes
MACHINE 1 MACHINE 2 MACHINE 3
B1 5 B2 3 C1 2
B3 7 C3 15 D3 5
C2 10 D2 8 D1 10
Sum * 17
* Bottleneck
Copyright 2006 John Wiley & Sons, Inc.

37. Synchronous Manufacturing (cont.)
Machine 1
Machine 3
Setup
Completion time
1002
2322 12
2732
200
1260
1940
2737 C2 B1 B3 C3 B2 D2 C1 D1 D3
Idle
1562
1512
1872
Machine 2 2
Copyright 2006 John Wiley & Sons, Inc.

38. Employee Scheduling Labor is very flexible resource
Scheduling workforce is complicated repetitive task
Assignment method can be used
Heuristics are commonly used
Copyright 2006 John Wiley & Sons, Inc.

39. Employee Scheduling Heuristic
Let N = no. of workers available Di = demand for workers on day i X = day working O = day off
Assign the first N - D1 workers day 1 off. Assign the next N - D2 workers day 2 off. Continue in a similar manner until all days are have been scheduled
If number of workdays for full time employee < 5, assign remaining workdays so consecutive days off are possible
Assign any remaining work to part-time employees
If consecutive days off are desired, consider switching schedules among days with the same demand requirements
Copyright 2006 John Wiley & Sons, Inc.

40. Employee Scheduling DAY OF WEEK M T W TH F SA SU MIN NO. OF
WORKERS REQUIRED
Taylor
Smith
Simpson
Allen
Dickerson
Copyright 2006 John Wiley & Sons, Inc.

41. Employee Scheduling (cont.)
DAY OF WEEK M T W TH F SA SU
MIN NO. OF
WORKERS REQUIRED
Taylor O X X O X X X
Smith O X X O X X X
Simpson X O X X O X X
Allen X O X X X X O
Dickerson X X O X X X O
Completed schedule satisfies requirements but has no consecutive days off
Copyright 2006 John Wiley & Sons, Inc.

42. Employee Scheduling (cont.)
DAY OF WEEK M T W TH F SA SU
MIN NO. OF
WORKERS REQUIRED
Taylor O O X X X X X
Smith O O X X X X X
Simpson X X O O X X X
Allen X X X O X X O
Dickerson X X X X O X O
Revised schedule satisfies requirements with consecutive days off for most employees
Copyright 2006 John Wiley & Sons, Inc.

43. Automated Scheduling Systems
Staff Scheduling
Schedule Bidding
Schedule Optimization
Copyright 2006 John Wiley & Sons, Inc.

44. Copyright 2006 John Wiley & Sons, Inc. All rights reserved
Copyright 2006 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information herein.
Copyright 2006 John Wiley & Sons, Inc.