I2 U Intelligent Supply Chain Management Course Module Fourteen: Production Scheduling

i2 UIntelligent Supply Chain Management

Course

Module Fourteen:Module Fourteen:Production SchedulingProduction Scheduling

2© 2001 i2 Technologies Inc CONFIDENTIAL

Supply Chain Management Key Processes

Sales & Operations Planning

Demand Planning

Inventory Planning

Supplier Scheduling

Production Scheduling

Inventory Deployment

Transportation Scheduling

Demand Fulfillment

Supply Chain Execution Monitoring

Strategic Supply Chain

Planning

Master Supply Planning

Procurement

Production Distribution

Transportation

Impact of decisions

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ions

+

_

Spec

ifici

ties

by in

dust

ries Length of Planning horizon

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ow

n d

irec

tio

ns

Fu

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Reaction to changing supply conditions


After Completing This Module,You are Expected to:

Explain the difference between production planning and production scheduling

Identify the key objectives of the Production Scheduling process

Understand in which production environments the Production Scheduling is critical, and in which it is not

Understand the logic of genetic algorithms and their value for the Production Scheduling process

Identify other key steps that need to be taken in addition to optimizing the Production Scheduling process to reach manufacturing excellence

Identify Production Scheduling key enablers and their resulting business value

Identify Production Scheduling excellence criteria


Production Scheduling Process Positioning

hou

rs

days

wee

ks

mon

ths

year

+

buy

make

move

sell

store

operational tactical strategicscheduling


The Difference Between Production Planning and Production Scheduling

PlanningPlanning

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6

54

3

2

1

7

6

5

4

3

2

1 1

2

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5

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7

Finds available material and capacity, then fills up “time buckets” with jobs until the bucket is full, without considering the specific sequence. Modeling:- Resources may be aggregated- Average production capacity- Detailed material requirements

Resource Time Buckets

Day 1 Day 2 Day 3

SchedulingScheduling

7654321

7654321 1

234567

Resource Time BucketsLooks at the contents of each “time bucket” obtained from the planning tool, then schedules the best sequence according to customer- defined constraints.Modeling:- Resources are assigned- Detailed production capacity- Critical material dependenciesDay 1 Day 2 Day 3

Min

ute

s


Production Scheduling Objectives

Ensure 100% production planning feasibility by not incorporating assumptions from plans (estimated set up time, aggregated resources, …) and respecting detailed constraints

Minimize set up time (labor costs) and maximize throughput


Criticality of Production Scheduling Depends on Changeover Cost and Frequency

Frequency of changeovers

Mass Customization

Make-to-Order

High

Low

Co

st/C

om

ple

xity

of

Ch

ang

eove

rs

Repetitive

Detailed Scheduling

Critical

Mixed Model


Certain Industries Get Larger Benefits Than Others

Frequency of Changeovers

High

Low

Co

st/C

om

ple

xity

of

Ch

ang

eove

rs MetalsMetals

Electronics/ PC Electronics/ PC ManufacturersManufacturers

CPGCPG

Job ShopsJob Shops

Heavy Heavy EquipmentEquipment

Automotive Automotive OEMsOEMs

AppliancesAppliances

CommoditiesCommodities

Mass Customization

Make-to-Order

Repetitive Mixed Model


A Simple Example Problem

6 Orders, 1 Machine Various due dates and production

times 2 different colors, 1 day changeover 6! = 720 permutations

Job Prod Days Color DueA 2 Blue 4B 3 Green 7C 1 Blue 8D 2 Blue 9E 3 Green 15F 2 Green 17


Definition of Constraints

Represent scheduling objectives; example : – Avoid late orders

– Reduce number of changeovers

Penalty points for constraint violations– 100 points for a late job

– 50 points for a changeover

Constraints are either hard or soft Each schedule is graded based on the constraints

– 2 late, 5 changeover = 450 points

Lowest score is the best


Traditional Scheduling Methods

JobDue

1 2 3 4 5 6 7 80 9 1112131410 15 1716 18

A4 B7 C8 D9 E15 F17

F17E15D9C8B7A4

A4 C8 E15 B7 D9 F17

Forward, by due date

2 late, 5 changeover = 450 ptsBackward, by due date

1 infeasible, 5 changeover = ? ptsColor Campaign

2 late, 1 changeover = 250 pts

Genetic Algorithm ???

D9 F17

A4

B7 D9


Genetic Algorithms: A New Approach to Complex Problems

Very much like bio-genetic technology

Concept invented at U of Michigan, ‘70’s

Based on optimizing “Population Genetics”

“Evolves” good schedules from a “population” of possible schedules


Genetic Algorithms - How it Works

Entire sequences are encoded like genes in a chromosome– a job is a gene

– a sequence of genes (jobs) is a chromosome

– a population is a group of chromosomes

A B C D E F

A BC D EF


Genetic Algorithms - How it Works

Survival of the fittest– Good sequences and their characteristics are saved

and used as the parents for the next generation– Bad sequences and characteristics are discarded

New sequences are generated

Many generations are tested

Best sequence selected


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2

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3

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Genetic Algorithms

Generates a random set of schedules at the first pass and gives penalty points

Then “cross-breeds” the best of breed schedules in the second pass and gives penalty points

Then “cross-breeds” the best of breed schedules in the third pass and gives penalty points

Then……and comes up with an optimal schedule!!


Genetic Algorithms Compared to Traditional Scheduling Methods

1 2 3 4 5 6 7 80 9 1112131410 15 1716 18

A4 B7 C8 D9 E15 F17

F17E15D9C8B7A4

A4 C8 E15 B7 D9 F17

Forward, by due date

2 late, 5 changeover = 450 ptsBackward, by due date

1 infeasible, 5 changeover = ? ptsColor Campaign


D9 F17

A4

B7 D9

B7 D9

Genetic Algorithm

A4 C8 F17 E15



Production Scheduling Process Key Enablers And Related Business Benefits

100% valid schedules ensured by considering ALL constraints

Best of breed logic to generate optimal schedules (genetic algorithm)

High speed schedule generation (easy what if simulations)

Customer service (delivery speed and reliability)

Throughput

Inventory turns


To Guarantee Valid Schedules,One Must be Able to Model All Types of Constraints

Sequence dependant set up Precedence rules Cool down time Tank scheduling Incompatible productions Task synchronization ...


© 2001 i2 Technologies Inc CONFIDENTIAL 20

Production Scheduling is Only One Ingredient Necessary to Reach Manufacturing Excellence

TQM techniques must be applied to maximize the manufacturing process predictability -- by minimizing :– Yield variation

– Lead time variation

Other TQM techniques must be considered to maximize the flexibility of the manufacturing process :

– Reduce the total production cycle time in order to move from a ‘Build to stock’ to a ‘Build to Order’ production process

– Changeover time reduction

– Design for manufacturability techniques

– Accelerated material flow through ‘Just-in-Time’ techniques



Changeover Time Reduction

Traditional Changeover Program Quick Changeover Program

• Plan changeover times and material schedule availability in advance

• Separate internal from external activities to minimize downtime

• Specify tasks and time duration for each member of the changeover team; error-proof the process

• Monitor and track results during the changeover and analyze the variance with corrective actions

Erratic, unpredictable higher changeover

times

Consistent, predictable lower changeover times

resulting in increased flexibility and

increased capacity

# of Changeovers # of Changeovers

Cha

ngeo

ver

time

Cha

ngeo

ver

time

© 2001 i2 Technologies Inc CONFIDENTIAL 23

Production Scheduling is Only One Ingredient Necessary to Reach Manufacturing Excellence

TQM techniques must be applied to maximize the manufacturing process predictability - by minimizing :

– Yield variation– Lead time variation

Other TQM techniques must be considered to maximize the flexibility of the manufacturing process :

– Reduce the total production cycle time in order to move from ‘Build to stock’ to ‘Build to Order’ production process

– Changeover time reduction – Design for manufacturability techniques– Accelerated material flow through ‘Just-in-Time’ techniques

Finally, manufacturing process simplicity must be achieved through techniques such as :

– Backflushing– Repetitive manufacturing– Flattened bill of materials– Simplified material flows (cellular manufacturing, focused factory, …)


Production Scheduling Process Excellence Criteria

All production constraints (including elements such as sequence dependent set-up, cool down time, precedence rules, task synchronization, … as well as material availability and delivery date) are considered when the production schedules are generated, thus ensuring that the schedules are 100% accurate and valid.

The right optimization technique is applied to generate the ‘best’ possible schedule in the shortest period of time.

The production scheduling process is tightly integrated with the Master Planning process. Changes in the production schedules are immediately reflected in the master plans.

The scheduling horizon is long enough to accommodate the entire order backlog.

Documents

I2 U Intelligent Supply Chain Management Course Module Fourteen: Production Scheduling