Transcript Detailed Scheduling (DS) EGN 5623 Enterprise Systems Optimization (Professional MSEM)

Detailed Scheduling (DS)
EGN 5623
Enterprise Systems Optimization
(Professional MSEM)
Fall, 2012
Detailed Scheduling (DS)
Theories & Concepts
EGN 5623
Enterprise Systems Optimization
(Professional MSEM)
Fall, 2012
Topics
•
DS concepts
1. Finite and infinite loading
2. Scheduling directions
3. Sequencing rules
4. Criteria for evaluation of sequencing rules
5. Controlling changeover costs
6. Minimize total production time
•
DS in SAP APO
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.

Scheduling and Shop-Floor
Decisions (Review)
Master
Production
Schedule (MPS)
Product Design
and
Process Plans
Material
Requirements
Plan (MRP)
Capacity
Requirements
Plan (CRP)
OrderProcessing 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
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
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Common Shop Floor Control
Activities
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The production control department
controls and monitors order progress
through the shop.
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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
Shop Floor Planning and Control
 Input-Output Control
 Gantt Chart
 Finite and Infinite Loading
 Forward and Backward Scheduling
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
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Gantt Charts
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Gantt charts are useful tools to coordinate
jobs through shop; graphical summary of
job status and loading of operations
Gantt Charts (Review)
Work Centers
Mon. Tue. Wed. Thu. Fri. Sat.
E
Machining
Fabrication
Assembly
C
F
D
H
E
C
Scheduled
F
D
H
Test
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C
Progress
E
D
Setup, Maint.
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
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Finite loading
◦ Uses work center capacity to schedule orders
◦ Popular scheduling approach
◦ Integral part of CRP
Assigning Jobs to Work Centers:
Which Job Gets Built First?
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Forward scheduling
◦ Jobs are given earliest available time slot in
operation
◦ excessive WIP usually results
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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
Order-Sequencing Problems
 Sequencing Rules
 Criteria for Evaluating
Sequencing
Rules
 Comparison of Sequencing Rules
 Controlling Changeover Costs
 Minimizing Total Production Time
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.
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Order-Sequencing Rules (Review)
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First-Come First-Served (FCFS)
Next job to process is the one that arrived first
among the waiting jobs
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Shortest Processing Time (SPT)
Next job to process is the one with the shortest
processing time among the waiting jobs
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Earliest Due Date (EDD)
Next job to process is the one with the earliest
due (promised finished) date among the waiting
jobs
Order-Sequencing Rules (Review)
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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
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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
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Least Changeover Cost (LCC)
Sequence the waiting jobs such that total
machine changeover cost is minimized
Evaluating the Effectiveness
of Sequencing Rules (Review)
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

Experience Says (Review)

First-come-first-served
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Shortest processing time
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Critical ratio
◦ Performs poorly on most evaluation criteria
◦ Does give customers a sense of fair play
◦ Performs well on most evaluation criteria
◦ But have to watch out for long-processing-time
orders getting continuously pushed back
◦ 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.
Controlling Changeover Costs
(Review)
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Changeover costs - costs of changing a
processing step in a production system
over from one job to another
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Changing machine settings
Getting job instructions
Changing material
Changing tools
Usually, jobs should be processed in a
sequence that minimizes changeover
costs
Controlling Changeover Costs
(Review)
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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
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
DS in SAP APO
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Tasks and activities of detailed scheduling
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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
Tasks of Detailed Scheduling
Detailed scheduling is used to:
1. Determine the resources and dates/times for carrying
out operations, taking resource and product availability
into consideration.
2. Support the scheduler in scheduling resources when
creating an optimal operations sequence.
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.
Activities of DS: Schedule
Schedule:
For an operation of a newly created order or for a deallocated operation
1. The resources are determined on which the operation
should be processed
2. 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.
Activities of DS: Reschedule
Reschedule:
1. A new date/time or new resources are specified for a
scheduled operation.
2. With rescheduling, the operation remains loaded on
resources.
3. After rescheduling, it loads either the previous resources
or the new resources.
4. Rescheduling an order means rescheduling all the
operations of the order.
Activities of DS: De-allocate
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Remove an operation from the resource schedule.
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With de-allocation, an operation is given the status
de-allocated. The operation no longer loads any
resources.
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De-allocating an order means de-allocating all the
operations of the order.
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An operation in the SAP APO system is
• either scheduled(with no separate status),
• or de-allocated (in this case it has the status deallocated).
Activities of DS: Adjust
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A new date/time or new resource is assigned to a deallocated operation.
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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.
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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.
Activities of DS: Fix
1. The resource and date/time for the operation is fixed.
2. Through the fixing process, a scheduled or de-allocated
operation is assigned the status fixed.
3. A fixed scheduled operation cannot be rescheduled or
de-allocated, and a fixed de-allocated operation cannot
be scheduled or adjusted.
Integrated Distribution &
Production Planning
SAP Implementation
EGN 5623
Enterprise Systems Optimization
(Professional MSEM)
Fall, 2012
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.
Production Planning Run
The user may execute planning online, or in the background
for selected orders:
1. online planning: for small data quantities (for
example, for test purposes),
2. background planning: for mass planning.
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.
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.
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).
SAP APO Planning Board (Interface)
SAP APO – Production Planning – Interactive Production Planning – Detailed
Scheduling – Detailed Scheduling Planning Board/Variable view
(APO/CDPS0)
SAP APO Planning Board
SAP APO – Production Planning – Interactive Production Planning – Detailed
Scheduling – Detailed Scheduling Planning Board/Variable view
(APO/CDPS0)
SAP APO Planning Board (Legend)
SAP APO – Production Planning – Interactive Production Planning – Detailed
Scheduling – Detailed Scheduling Planning Board/Variable view
(APO/CDPS0)
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.
Detailed Scheduling Heuristics
DS Heuristic Activities
1. 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.
2. 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.
Homework for DS
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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