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

Detailed Scheduling (DS)Detailed Scheduling (DS)

EGN 5623 Enterprise Systems Optimization EGN 5623 Enterprise Systems Optimization(Professional MSEM)(Professional MSEM)

Fall, 2012 Fall, 2012

Detailed Scheduling (DS)Detailed Scheduling (DS)

Theories & ConceptsTheories & Concepts


Fall, 2012Fall, 2012

TopicsTopics • DS concepts

1. Finite and infinite loading2. Scheduling directions3. Sequencing rules4. Criteria for evaluation of sequencing rules5. Controlling changeover costs6. Minimize total production time

• DS in SAP APO

Process-Focused OperationsProcess-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 Scheduling and Shop-Floor Decisions (Review)Decisions (Review)

MaterialMaterialRequirementsRequirementsPlan (MRP)Plan (MRP)

CapacityCapacityRequirementsRequirementsPlan (CRP)Plan (CRP)

Order-Order-Processing orProcessing orRouting PlansRouting Plans

Planned Planned Order ReleasesOrder Releases

ReportReport

Work CenterWork CenterLoading andLoading and

Overtime PlanOvertime Plan

Assignment ofAssignment ofOrders toOrders to

Work CentersWork Centers

MasterMasterProductionProduction

Schedule (MPS)Schedule (MPS)

Product DesignProduct Designandand

Process PlansProcess Plans

Day-to-Day Scheduling and Shop-Floor DecisionsDay-to-Day Scheduling and Shop-Floor Decisions

Pre-production PlanningPre-production PlanningDesign the product in customer orderPlan the operations the product must pass

through ..... this is the routing planWork moves between operations on a

move ticket

Common Shop Floor Control Common Shop Floor Control ActivitiesActivities

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

Shop Floor Planning and ControlShop Floor Planning and Control

Input-Output ControlGantt ChartFinite and Infinite LoadingForward and Backward Scheduling

Input-Output ControlInput-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

Gantt ChartsGantt ChartsGantt charts are useful tools to coordinate

jobs through shop; graphical summary of job status and loading of operations

Gantt Charts (Review)Gantt Charts (Review)

MachiningMachining

FabricationFabrication

AssemblyAssembly

TestTest

Tue.Tue. Wed.Wed. Thu.Thu. Fri.Fri. Sat.Sat.Work CentersWork Centers Mon.Mon.

E F G

C D E

H C

F

ED

H C D

ScheduledScheduled ProgressProgress Setup, Maint.Setup, Maint.

Assigning Jobs to Work Centers:Assigning Jobs to Work Centers:How Many Jobs/Day/Work CenterHow Many Jobs/Day/Work CenterInfinite 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

Assigning Jobs to Work Centers:Assigning Jobs to Work Centers:Which Job Gets Built First?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

Order-Sequencing ProblemsOrder-Sequencing ProblemsSequencing RulesCriteria for Evaluating Sequencing

RulesComparison of Sequencing RulesControlling Changeover CostsMinimizing Total Production Time

Order-Sequencing ProblemsOrder-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.

Order-Sequencing Rules (Review)Order-Sequencing Rules (Review)

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

Order-Sequencing Rules (Review)Order-Sequencing Rules (Review)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

Evaluating the EffectivenessEvaluating the Effectivenessof Sequencing Rules (Review)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)Experience Says (Review)First-come-first-served

◦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 backCritical 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.

Controlling Changeover Costs Controlling Changeover Costs (Review)(Review)

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

Controlling Changeover Costs Controlling Changeover Costs (Review)(Review)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 TimeMinimizing Total Production TimeSequencing 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 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

Tasks of Detailed SchedulingTasks 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 Activities of Detailed SchedulingScheduling 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: ScheduleActivities of DS: Schedule

Schedule:For an operation of a newly created order or for a de-allocated operation1.The resources are determined on which the operation should be processed2.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: RescheduleActivities 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-allocateActivities 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).

Activities of DS: AdjustActivities 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.

Activities of DS: FixActivities 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 & Integrated Distribution & Production Planning Production Planning

SAP Implementation SAP Implementation


Fall, 2012 Fall, 2012

Prerequisites of DSPrerequisites 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 RunProduction 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 BoardDetailed Scheduling Planning Board Purpose:

•Graphical representation of the planning situationGraphically 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 problemsYou 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 BoardDetailed 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 BoardDetailed Scheduling Planning Board

Layout of the Detailed Scheduling Planning BoardWhen 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 Planning Board (Interface)

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

SAP APO Planning BoardSAP APO Planning Board


SAP APO Planning Board (Legend)SAP APO Planning Board (Legend)


Detailed Scheduling HeuristicsDetailed Scheduling Heuristics DS Heuristics Features:

• Strategy settingsDepending 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 periodThe system uses heuristics to reschedule operations that start in the planning period.

Detailed Scheduling HeuristicsDetailed Scheduling Heuristics

DS Heuristic Activities1.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 DSHomework for DS

1. Change demands for Distribution centers2. Run network plan with multilevel heuristic3. Review planning board4. Define SNP deployment profile5. Define transport load builder profile (TLB)6. Assign TLB profile to the transportation lanes7. Run deployment heuristics

Documents

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