1. Detailed Scheduling (DS) EGN 5623 Enterprise Systems Optimization (Professional MSEM) Fall, 2012

2. Detailed Scheduling (DS) Theories & Concepts EGN Enterprise Systems Optimization (Professional MSEM) Fall, 2012

3. Topics DS concepts Finite and infinite loading Scheduling directions
Sequencing rules
Criteria for evaluation of sequencing rules
Example for comparison of sequencing rules
Controlling changeover costs
Minimize total production time
Assignment problems
DS in SAP APO

4. Process-Focused Operations
Process-focused factories are often called job shops.
A job shop’s work centers are organized around similar types of equipment or operations.
Workers and machines are flexible and can be assigned to and reassigned to many different orders.
Job shops are complex to schedule.

5. Scheduling and Shop-Floor Decisions
Master
Production
Schedule (MPS)
Product Design
and
Process Plans
Material
Requirements
Plan (MRP)
Capacity
Requirements
Plan (CRP)
Order-
Processing or
Routing Plans
Planned
Order Releases
Report
Work Center
Loading and
Overtime Plan
Assignment of
Orders to
Work Centers
Day-to-Day Scheduling and Shop-Floor Decisions

6. Pre-production Planning
Design the product in customer order
Plan the operations the product must pass through this is the routing plan
Work moves between operations on a move ticket

7. Common Shop Floor Control Activities
The production control department controls and monitors order progress through the shop.
Assigns priority to orders
Issues dispatching lists
Tracks WIP and keeps systems updated
Controls input-output between work centers
Measures efficiency, utilization, and productivity of shop

8. Shop Floor Planning and Control
Input-Output Control
Gantt Chart
Finite and Infinite Loading
Forward and Backward Scheduling

9. Input-Output Control
Input-output control identifies problems such as insufficient or excessive capacity or any issues that prevents the order from being completed on time.
Input-output control report compares planned and actual input, planned and actual output, and planned and actual WIP in each time period

10. Gantt Charts
Gantt charts are useful tools to coordinate jobs through shop; graphical summary of job status and loading of operations

11. Gantt Charts Work Centers Mon. Tue. Wed. Thu. Fri. Sat. Machining
Fabrication
Assembly
Test E F G C D E F H C D E H C D
Gantt Charts
Scheduled
Progress
Setup, Maint.

12. Assigning Jobs to Work Centers: How Many Jobs/Day/Work Center
Infinite loading
Assigns jobs to work centers without regard to capacity
Unless excessive capacity exists, long queues occur
Finite loading
Uses work center capacity to schedule orders
Popular scheduling approach
Integral part of CRP

13. Assigning Jobs to Work Centers: Which Job Gets Built First?
Forward scheduling
Jobs are given earliest available time slot in operation
excessive WIP usually results
Backward scheduling
Start with promise date and work backward through operations reviewing lead times to determine when a job has to pass through each operation
Less WIP but must have accurate lead times

14. Order-Sequencing Problems
Sequencing Rules
Criteria for Evaluating Sequencing Rules
Comparison of Sequencing Rules
Controlling Changeover Costs
Minimizing Total Production Time

15. Order-Sequencing Problems
We want to determine the sequence in which we will process a group of waiting orders at a work center.
Many different sequencing rules can be followed in setting the priorities among orders.
There are numerous criteria for evaluating the effectiveness of the sequencing rules.

16. Order-Sequencing Rules
First-Come First-Served (FCFS)
Next job to process is the one that arrived first among the waiting jobs
Shortest Processing Time (SPT)
Next job to process is the one with the shortest processing time among the waiting jobs
Earliest Due Date (EDD)
Next job to process is the one with the earliest due (promised finished) date among the waiting jobs

17. Order-Sequencing Rules
Least Slack (LS)
Next job to process is the one with the least [time to due date minus total remaining processing time] among the waiting jobs
Critical Ratio (CR)
Next job to process is the one with the least [time to due date divided by total remaining processing time] among the waiting jobs
Least Changeover Cost (LCC)
Sequence the waiting jobs such that total machine changeover cost is minimized

18. Evaluating the Effectiveness of Sequencing Rules
Average flow time - average amount of time jobs spend in shop
Average number of jobs in system -
Average job lateness - average amount of time job’s completion date exceeds its promised delivery date
Changeover cost - total cost of making machine changeovers for group of jobs

19. Experience Says: First-come-first-served Shortest processing time
Performs poorly on most evaluation criteria
Does give customers a sense of fair play
Shortest processing time
Performs well on most evaluation criteria
But have to watch out for long-processing-time orders getting continuously pushed back
Critical ratio
Works well on average job lateness criterion
May focus too much on jobs that cannot be completed on time, causing others to be late too.

20. Example: Sequencing Rules
Use the FCFS, SPT, and Critical Ratio rules to sequence the five jobs below. Evaluate the rules on the bases of average flow time, average number of jobs in the system, and average job lateness.
Job Processing Time Time to Promised Completion
A hours 10 hours B C D E

21. Example: Sequencing Rules
FCFS Rule A > B > C > D > E
Processing Promised Flow
Job Time Completion Time Lateness A B C D E

22. Example: Sequencing Rules
FCFS Rule Performance
Average flow time:
141/5 = 28.2 hours
Average number of jobs in the system:
141/49 = 2.88 jobs
Average job lateness:
90/5 = 18.0 hours

23. Example: Sequencing Rules
SPT Rule A > E > C > B > D
Processing Promised Flow
Job Time Completion Time Lateness A B C D E

24. Example: Sequencing Rules
SPT Rule Performance
Average flow time:
127/5 = 25.4 hours
Average number of jobs in the system:
127/49 = 2.59 jobs
Average job lateness:
76/5 = 15.2 hours

25. Example: Sequencing Rules
Critical Ratio Rule E > C > D > B > A
Processing Promised Flow
Job Time Completion Time Lateness
E (.875)
C (.889)
D (1.00)
B (1.33)
A (1.67)

26. Example: Sequencing Rules
Critical Ratio Rule Performance
Average flow time:
148/5 = 29.6 hours
Average number of jobs in the system:
148/49 = 3.02 jobs
Average job lateness:
93/5 = 18.6 hours

27. Example: Sequencing Rules
Comparison of Rule Performance
Average Average Average
Flow Number of Jobs Job
Rule Time in System Lateness
FCFS
SPT CR
SPT rule was superior for all 3 performance criteria.

28. Controlling Changeover Costs
Changeover costs - costs of changing a processing step in a production system over from one job to another
Changing machine settings
Getting job instructions
Changing material
Changing tools
Usually, jobs should be processed in a sequence that minimizes changeover costs

29. Controlling Changeover Costs
Job Sequencing Heuristic
First, select the lowest changeover cost among all changeovers (this establishes the first two jobs in the sequence)
The next job to be selected will have the lowest changeover cost among the remaining jobs that follow the previously selected job

30. Example: Minimizing Changeover Costs
Hardtimes Heat Treating Service has 5 jobs waiting to be processed at work center #11. The job-to-job changeover costs are listed below. What should the job sequence be?
Jobs That Precede
A B C D E A B C D E
Jobs
That
Follow

31. Example: Minimizing Changeover Costs
Develop a job sequence:
A follows D ($50 is the least c.o. cost)
C follows A ($92 is the least following c.o. cost)
B follows C ($69 is the least following c.o. cost)
E follows B (E is the only remaining job)
Job sequence is D – A – C – B – E
Total changeover cost = $ = $286

32. Minimizing Total Production Time
Sequencing n Jobs through Two Work Centers
When several jobs must be sequenced through two work centers, we may want to select a sequence that must hold for both work centers
Johnson’s rule can be used to find the sequence that minimizes the total production time through both work centers

33. Johnson’s Rule
1. Select the shortest processing time in either work center
2. If the shortest time is at the first work center, put the job in the first unassigned slot in the schedule. If the shortest time is at the second work center, put the job in the last unassigned slot in the schedule.
3. Eliminate the job assigned in step 2.
4. Repeat steps 1-3, filling the schedule from the front and back, until all jobs have been assigned a slot.

34. Example: Minimizing Total Production Time
It is early Saturday morning and The Finest Detail has five automobiles waiting for detailing service. Each vehicle goes through a thorough exterior wash/wax process and then an interior vacuum/shampoo/polish process.
The entire detailing crew must stay until the last vehicle is completed. If the five vehicles are sequenced so that the total processing time is minimized, when can the crew go home. They will start the first vehicle at 7:30 a.m.
Time estimates are shown on the next slide.

35. Example: Minimizing Total Production Time
Exterior Interior
Job Time (hrs.) Time (hrs.)
Cadillac
Bentley
Lexus
Porsche
Infiniti

36. Example: Minimizing Total Production Time
Johnson’s Rule
Least Work Schedule
Time Job Center Slot
Infiniti Interior 5th
1.6 Porsche Interior 4th
1.9 Lexus Exterior 1st
2.0 Cadillac Exterior 2nd
2.1 Bentley Exterior 3rd

37. Example: Minimizing Total Production Time
Exterior
Interior L C B P I
Idle
Idle L C B P I
It will take from 7:30 a.m. until 7:30 p.m. (not
allowing for breaks) to complete the five vehicles.

38. Minimize Total Production Time

39. Minimize Total Production Time

40. Minimize Total Production Time

41. Minimize Total Production Time

42. DS in SAP APO Tasks and activities of detailed scheduling
Controlling Detailed Scheduling
Dates/Times and Planning Directions
Resource Availability
Selection of Resources
Time Relationships
Pegging Relationships
Automatic Propagation of Changes
Determining the Setup Time for Sequence-Dependent Setup Activities
Synchronizing Activities on Multi-resources
Block planning
Scheduling Log
Terminating Scheduling
Detailed Scheduling Heuristics

43. Tasks of Detailed Scheduling
Detailed scheduling is used to:
 Determine the resources and dates/times for carrying out operations, taking resource and product availability into consideration.
Support the scheduler in scheduling resources when creating an optimal operations sequence.

44. Activities of Detailed Scheduling
Basic DS Activities:
Scheduling
dispatching operations to resources at a specific date/time
Rescheduling
dispatching already scheduled operations to a different date/time or to different resources
De-allocating
removing scheduled operations from the resource schedule
Adjusting
a new date/time or new resources are assigned to a de-allocated operation.
Fixing
the resource and date/time for the operation is fixed.

45. Activities of DS: Schedule
For an operation of a newly created order or for a de-allocated operation
The resources are determined on which the operation should be processed
The date/time is determined when the operation should be processed on the resources
With scheduling, the operation is dispatched to the resources. Scheduling an order means scheduling all the operations of the order.

46. Activities of DS: Reschedule
A new date/time or new resources are specified for a scheduled operation.
With rescheduling, the operation remains loaded on resources.
After rescheduling, it loads either the previous resources or the new resources.
Rescheduling an order means rescheduling all the operations of the order.

47. Activities of DS: De-allocate
Remove an operation from the resource schedule.
With de-allocation, an operation is given the status de-allocated. The operation no longer loads any resources.
De-allocating an order means de-allocating all the operations of the order.
An operation in the SAP APO system is
either scheduled(with no separate status),
or de-allocated (in this case it has the status de-allocated).

48. Activities of DS: Adjust
A new date/time or new resource is assigned to a de-allocated operation.
In the case of an adjustment, the operation retains the status de-allocated. The operation does not load the resources to which it is assigned. Adjusting does not change any resources schedules.
Adjusting is a detailed scheduling activity that is carried out automatically by the system for dependent objects (for example, if relationships or pegging relationships have to be adhered to). You cannot adjust de-allocated operations manually.

49. Activities of DS: Fix
The resource and date/time for the operation is fixed.
Through the fixing process, a scheduled or de-allocated operation is assigned the status fixed.
A fixed scheduled operation cannot be rescheduled or de-allocated, and a fixed de-allocated operation cannot be scheduled or adjusted.

50. Integrated Distribution & Production Planning SAP Implementation EGN Enterprise Systems Optimization (Professional MSEM) Fall, 2012

51. Prerequisites of DS
The system can trigger detailed scheduling activities automatically. For example, it automatically schedules the order operations when an order is created.
Three ways to start detailed scheduling activities:
production planning run,
detailed scheduling planning board, or
resource planning table specifically for selected operations or orders.

52. Production Planning Run
The user may execute planning online, or in the background for selected orders:
online planning: for small data quantities (for example, for test purposes),
background planning: for mass planning.

53. Detailed Scheduling Planning Board
 Purpose:
Graphical representation of the planning situation
Graphically represent different aspects of scheduling in the charts of the detailed scheduling planning board. For example, you can show the situation of operations on resources over time and the development of the resource utilization or pegging relationships between orders over time.
Interactive solution of planning problems
You can perform interactive scheduling on the detailed scheduling planning board to solve scheduling problems such as sequence or date/time problems on resources. Various scheduling functions and heuristics are available in addition to manual scheduling with Drag&Drop.

54. Detailed Scheduling Planning Board
Integration
The detailed scheduling planning board is integrated in different Production Planning applications.
You can call up the detailed scheduling planning board directly:
In the area menu for production planning
In order processing
In the product planning table
SAP provides the detailed scheduling planning board with standard settings (for example, for setup or layout). If you want to configure a detailed scheduling planning board for your specific scheduling requirements, you must make the appropriate settings.

55. Detailed Scheduling Planning Board
Layout of the Detailed Scheduling Planning Board
When you invoke the detailed scheduling planning board for the first time, the selection area is shown in the left-hand part of the screen. You can control the display of the selection area via Settings -> User Settings and save the setting on a user-specific basis.
The setting you make on the detailed scheduling planning board is independent of the setting in the resource planning table (see Configuring the Resource Planning Table).
The selection area serves to provide an overview of the loaded products and resources and to show and hide objects (see Hiding and Showing Objects).

56. SAP APO Planning Board (Interface)
SAP APO – Production Planning – Interactive Production Planning – Detailed Scheduling – Detailed Scheduling Planning Board/Variable view
(APO/CDPS0)

57. SAP APO Planning Board
SAP APO – Production Planning – Interactive Production Planning – Detailed Scheduling – Detailed Scheduling Planning Board/Variable view
(APO/CDPS0)

58. SAP APO Planning Board (Legend)
SAP APO – Production Planning – Interactive Production Planning – Detailed Scheduling – Detailed Scheduling Planning Board/Variable view
(APO/CDPS0)

59. Detailed Scheduling Heuristics
DS Heuristics Features:
Strategy settings
Depending on the heuristic, you can change the selected strategy settings that the heuristic uses to schedule or reschedule operations. Certain strategy settings are permanently set by SAP and cannot be changed.
Planning period
The system uses heuristics to reschedule operations that start in the planning period.

60. Detailed Scheduling Heuristics
DS Heuristic Activities
If you want to start a heuristic on the DS planning board, select the desired objects and call up the heuristic by choosing Functions Heuristics. You can change the settings for the heuristics on the DS planning board by choosing Settings  Heuristics.
If you want to use a heuristic in the production planning run, enter the heuristic and the objects for which you want to execute the heuristic in the corresponding processing step in the production planning run.

61. Homework for DS Change demands for Distribution centers
Run network plan with multilevel heuristic
Review planning board
Define SNP deployment profile
Define transport load builder profile (TLB)
Assign TLB profile to the transportation lanes
Run deployment heuristics