Supporting Slides

Systems for Planning & Control in Manufacturing

Produced by D K Harrison and D J Petty 21/04/02 Sld - 0000

XSupporting Slides

Professor David K HarrisonGlasgow Caledonian University

Dr David J PettyThe University of Manchester Institute of Science and Technology

Systems for Planning & Control in Manufacturing:Systems and Management for Competitive Manufacture

ISBN 0 7506 49771


Produced by D K Harrison and D J Petty 21/04/02 Sld -

Finite Capacity Scheduling (FCS)

• Doubts Over MRPII by 1980's

• Use of JIT Techniques

• Development of OPT by Goldratt in 1970's

• Publication of "The Goal"

• Marketing of the OPT Software Package

• This Section Will Examine FCS, ICS and OPT

19

1901



MRP Limitations

Job AQuantity 100Due Date 07/10Operation 10 Work Centre 001

Set Time 60 MinsUnit Time 2 Mins

20 Work Centre 002Set Time 120 MinsUnit Time 3 Mins

Job BQuantity 100Due Date 07/10Operation 10 Work Centre 001

Set Time 120 MinsUnit Time 4 Mins

20 Work Centre 002Set Time 60 MinsUnit Time 1.5 Mins

WorkCentre

001

WorkCentre

002

Total Time to Manufacture A = 11.33Hrs

Total Time to Manufacture B = 12.17Hrs

MRP Assumptions:Fixed Lot SizesFixed Lead Times

What is the BestSequence for Manufacture?

19

1902



Finite and Infinite Scheduling

MRP - Infinite, Backward Scheduling Method

FCS - Finite, Forward Scheduling Method

DueDate

NowStartDate

DueDate

NowStartDate

Lead Time

MRP - Assumes Dominant Queuing Time

19

Time Base Time Base

1903



Data 1 – Workcentres

1029

1013

1019

1023

EfficiencyFactor: 90%




£50/Hr

£40/Hr

£45/Hr

£25/Hr

2 ShiftPattern

2 ShiftPattern

2 ShiftPattern

2 ShiftPattern

8 Hoursper Shift

8 Hoursper Shift

8 Hoursper Shift

8 Hoursper Shift

1 M/Cin Group

1 M/Cin Group

1 M/Cin Group

1 M/Cin Group

ForgingPress

Lathe

VerticalMill

Drill

19

1904



Data 2 - Routings

Operation 10W/C 1029

Ts = 90 MinsTp = 2 MinsTm = 240 MinsTq = 480 Mins

Set press to 15T.



Turn complete to drawing. Use NC tape number1938-0484.



Mill slots and inlet pockets to drawing. Use NC tape 1264-9888.



Drill 15 holes, evenly spaced.

Item Number: GDS8975T

19

1905



Example RoutingJob 1

Job 2

Job 3

Job 4

Job 5

Job 6

Op 1. R1 Op 2. R2 Op 3. R3 Op 4. R6

Op 1. R1 Op 2. R2 Op 3. R4 Op 4. R5

Op 1. R4 Op 2. R1 Op 3. R3 Op 4. R5

Op 1. R5 Op 2. R1 Op 3. R4

Op 1. R6 Op 2. R4 Op 3. R2 Op 4. R1

Op 1. R2 R3Op 2. Op 3. R5 Op 4. R4

Op 4. R6

R1 R3

R4

R5

R6R2

sijpijsjOpij T.TLT

19

Op. = OperationR = Resource

Op 4. R6

Operation 4 on Resource 6

1906



Infinite Scheduling - ExampleO

p 1

.R

1O

p 1

.R

1

Op

1.

R4

Op

1.

R5

Op

1.

R6

Op

1.

R2

Op

2.

R2

Op

2.

R2

Op

2.

R1

Op

2.

R1

Op

2.

R4

R3

Op

2.

Op

3.

R3

Op

3.

R4O

p 3

.R

3

Op

3.

R4

Op

3.

R2

Op

3.

R5

Op

4.

R6

Op

4.

R5

Op

4.

R5

Op

4.

R1

Op

4.

R4

Op

4.

R6

R1LoadHrs

Time (Days)

R2LoadHrs R3

LoadHrs R4

LoadHrs R5

LoadHrs R6

LoadHrs

Overload

Overload

Job 1

Job 2

Job 3

Job 4

Job 5

Job 6

Op 1. R1 Op 2. R2 Op 3. R3 Op 4. R6

Op 1. R1 Op 2. R2 Op 3. R4 Op 4. R5

Op 1. R4 Op 2. R1 Op 3. R3 Op 4. R5

Op 1. R5 Op 2. R1 Op 3. R4

Op 1. R6 Op 2. R4 Op 3. R2 Op 4. R1

Op 1. R2 R3Op 2. Op 3. R5 Op 4. R4

Op 4. R6

DueDate

Lead Time

Job 1

Job 2

Job 3

Job 4

Job 5

Job 6

Op 1. Op 2. Op 3. Op 4.

Start Date

Cap. Cap. Cap. Cap. Cap.

Cap.

5 6 7 8

Time (Days)

5 6 7 8

Time (Days)

5 6 7 8

Time (Days)

5 6 7 8

Time (Days)

5 6 7 8

Time (Days)

5 6 7 8

19

1907



Infinite Scheduling - Key Points

• Jobs Never Late by Definition

• Problems Shown by Overloads

• Does not Provide Solutions

• Called CRP with MRPII/ERP

19

1908



Finite Capacity Scheduling (1)

1 Determine Priority Sequence

2 Load Jobs Progressively

3 Optimise Schedule

• Different Methods Available

• Computers Commonly Used

• Manual Methods (e.g. Gantt Charts) Available

GeneralApproach

19

1909




Job 1

Job 2

Job 3

Job 4

Job 5

Job 6

Op 1. R1 Op 2. R2 Op 3. R3 Op 4. R6

Op 1. R1 Op 2. R2 Op 3. R4 Op 4. R5

Op 1. R4 Op 2. R1 Op 3. R3 Op 4. R5

Op 1. R5 Op 2. R1 Op 3. R4

Op 1. R6 Op 2. R4 Op 3. R2 Op 4. R1

Op 1. R2 R3Op 2. Op 3. R5 Op 4. R4

R1

R2

R3

R4

R5

R6

Op 4. R6

Time

19

1910




Job 1

Job 2

Job 3

Job 4

Job 5

Job 6

Op 1. R1 Op 2. R2 Op 3. R3 Op 4. R6

Op 1. R1 Op 2. R2 Op 3. R4 Op 4. R5

Op 1. R4 Op 2. R1 Op 3. R3 Op 4. R5

Op 1. R5 Op 2. R1 Op 3. R4

Op 1. R6 Op 2. R4 Op 3. R2 Op 4. R1

Op 1. R2 R3Op 2. Op 3. R5 Op 4. R4

R1

R2

R3

R4

R5

R6

Op 1. R1

Op 2. R2

Op 3. R3

Op 4. R6

Op 4. R6

Time

19

Op 1. R1

1911




Job 1

Job 2

Job 3

Job 4

Job 5

Job 6

Op 1. R1 Op 2. R2 Op 3. R3 Op 4. R6

Op 1. R1 Op 2. R2 Op 3. R4 Op 4. R5

Op 1. R4 Op 2. R1 Op 3. R3 Op 4. R5

Op 1. R5 Op 2. R1 Op 3. R4

Op 1. R6 Op 2. R4 Op 3. R2 Op 4. R1

Op 1. R2 R3Op 2. Op 3. R5 Op 4. R4

R1

R2

R3

R4

R5

R6

Op 1. R1

Op 2. R2

Op 3. R3

Op 4. R6

Op 4. R6

Time

Op 1. R1

Op 2. R2

Op 3. R4

Op 4. R5

19

1912




Job 1

Job 2

Job 3

Job 4

Job 5

Job 6

Op 1. R1 Op 2. R2 Op 3. R3 Op 4. R6

Op 1. R1 Op 2. R2 Op 3. R4 Op 4. R5

Op 1. R4 Op 2. R1 Op 3. R3 Op 4. R5

Op 1. R5 Op 2. R1 Op 3. R4

Op 1. R6 Op 2. R4 Op 3. R2 Op 4. R1

Op 1. R2 R3Op 2. Op 3. R5 Op 4. R4

R1

R2

R3

R4

R5

R6

Op 1. R1

Op 2. R2

Op 3. R3

Op 4. R6

Op 4. R6

Time

Op 1. R1

Op 2. R2

Op 3. R4

Op 4. R5

Op 1. R4

Op 2. R1

Op 3. R3

Op 4. R5Op 1. R5

Op 4. R6

Op 2. R1

Op 3. R4

Op 1. R6

Op 2. R4

Op 3. R2

Op 4. R1

Op 1. R2

R3Op 2.

Op 3. R5

Op 4. R4

19

1913



Finite Scheduling - Key Points

• Resources Never Overloaded

• Problems Shown by Lateness

• Ignores Subjective Factors

19

1914



Schedule Optimisation

R1

R2

R3

R4

R5

R6

Op 1. R1

Op 2. R2

Op 3. R3

Op 4. R6

Time

Op 1. R1

Op 2. R2

Op 3. R4

Op 4. R5

Op 1. R4

Op 2. R1

Op 3. R3

Op 4. R5Op 1. R5

Op 4. R6

Op 2. R1

Op 3. R4

Op 1. R6

Op 2. R4

Op 3. R2

Op 4. R1

Op 1. R2

R3Op 2.

Op 3. R5

Op 4. R4

Idle

• Is this the Best Schedule?

• Objective Functions

• Permutations = mn

Queue

• Minimum Makespan

• Minimum Tardiness

• Maximum Profit

19

1915



Johnson’s Algorithm

Select Smallest Time

Occurs at Machine 1?

Place as Near to End as Possible

Place as Near to Beginning as Possible

Yes

NoLast Job?

Yes

List Jobs and

Times

No

FinishQueueMachine

1Machine

2

Which Sequence Will Minimise Makespan?

Machine

Job Time (1) Time (2) Seq.A

B

C

D

E

F

G

H

I

J

6

5

11

4

9

10

13

7

8

8

7

4

5

8

12

13

9

10

9

6

19

1916



Work-to-ListsMRP Due

Date

MRP StartDate

Op 10Op 20

Op 30Op 40Back Scheduling

Logic

Prioritisation Rules

Work Centre 0290 Centre Lathes Issue Date 17/04/05

Work OrderNumber

PartNumber

Operation DueDue Date

3000167

3000369

3000258

3000198

3000153

GOS1365

GDS1987

PFF1888

TDS3687

TDS9637

06/05/05

07/05/05

12/05/05

16/05/05

17/05/05

Next WorkCentre

Previous

Work Centre

Order Due

Date

18/04/05

18/04/05

18/04/05

18/04/05

19/04/05

0360

0360

0380

0360

0360

0370

0370

0370

0420

0410

Quantity

1000

1000

1000

1000

1000

• Issued to Each Work Centre

• Means of Detailed Control

• Issued Daily

19

1917



Prioritisation and Sequencing – 1

• SPT*• EDD*• LPT

m n

Today DueTime Available (T )a

• Static Rules

19

1918




• Dynamic Rules

• FIFO*• Cr*• LS*• LSPRO*

B.Eq...T.TL - TSlack ni

misipisa

C.Eq...

mn

T.TL - TSPRO

ni

misipisa

A.Eq...

T

TTLC

a

ni

misipis

r

m n


19

1919




• Least Loaded Next W/C• Easiest Next Set-up*• Biggest Bonus• Who Shouts Loudest• Undefined

• Informal Rules

m n


19

1920




ABCDEFGHIJ

Priority List

SelectionWindowThis Approach is a Compromise Between

Set-Up Time and Manufacturing in a sequence related to Customer Requirements

19

1921



Shop Floor Feedback• Completions • Time Required

• Process Data• Labour Productivity

M/C Efficiency• M/C Breakdowns• Scrap• Rework• Defect Analysis

• Remote Entry

• Shop Floor Terminals

• Data Collection

<102394>

Smart

Tag

Direct

Interface

Controller

Transducer

Hand Held

Computer

SoftwareApplication

19

1922



Short Interval Scheduling (SIS)

UploadDownloadInterface

• Hybrid Approach

• Simulation

• What-if AnalysisOperationalRough Cut Capacity Planning

• Cannot Cope with a Heavily Overloaded Situation

SISSystem

Material Requirements Planning

Master Production Scheduling

Sales and Operations Planning

BusinessPlanning

Capacity Requirements Planning

Realistic

Shop Floor Control

No

Yes

Purchasing

19

1923



Rough Cut Capacity Planning – 1

Objective: to Check that the MPS is Valid

MPS

RCCP Resources• Production Line• Critical Work Centres• Labour• Key Supplier Capacity• Testing

Product Load Profile

Resource Load Profile

Time

Capacity

Load Per Unit

LoadTime Before Due Date

19

1924



Rough Cut Capacity Planning – 2

Objectives

• Checks MPS Validity• Shows Impact of Product Mix• Allows "What-if" Analysis

Limitations

• Only Consider Key Resources• Ignores Inventory of Components• Does not Monitor Work Order Execution

19

1925



RCCP vs CRP

Definition

Method

Frequency

Objective

Precision

Data

Speed

Use

RCCP CRP

Calculation based on all works orders

As required

1. Post-MRP analysis2. Determining bottlenecks

Aggregate Detailed

MPS and product load profiles

Fast Typically longer than MRP

Virtually all users of formal A minority of usersmanufacturing management Systems

Detailed evaluation of loadbased at work centre level

Estimated Load on critical resources based on MPS

Following each MRP run -typically once a week

1. Pre-MRP evaluation of MPS2. Operational planning

Works orders, work centres,routings and works order status

Use of MPS and product load profiles

19

1926



Disadvantages of CRP

• Data Hungry

• Need for Feedback

• Timing of Information

19

1927



OPT Background

• Doubts Over MRPII

• Developed by Dr EM Goldratt in the 1970s.

• OPT has Two ElementsPhilosophicalFinite Scheduling Algorithm

19

1928



OPT Principles

"The Goal" - To Make Money

OPT Emphasises the Importance of Bottlenecks. A Bottleneck is any Resource where Capacity is less than Load

Operating Expense

Inventory

Throughput

Cash Flow

ROCE

Net Profit

19

1929



Ten Rules of OPT

1. Balance flow, not capacity.

2. The level of utilisation of a non-bottleneck is determined not byits own potential, but by some other constraint in the system.

3. Utilisation and activation of a resource are not necessarily the same thing.

4. An hour lost at a bottleneck is an hour lost for the total system.

5. An hour saved at a non-bottleneck is a mirage.

6. Bottlenecks govern both throughput and inventory.

7. The transfer batch may not, and many times should not, be equalto the process batch.

8. The process batch should be variable, not fixed.

9. Capacity and priority should be considered simultaneously, not sequentially.

10. The sum of local optima is not equal to the optimum of the whole system.

19

1930



Process and Transfer Batches - 1 19

Standard Case – Process Batch and Transfer Batch the Same Size

Operation 10

Operation 20

Operation 30

Operation 40

Process Batch Larger than the Transfer Batch

Op 10

Op 20

Op 30

Op 40

1931



OPT Mechanics

BOM

BUILDNET

Routing

Initial SERVE

AnalysisSPLIT

OPTNetwork

SERVENetwork

SERVE

OPT

Non-CriticalResourceSchedule

CriticalResourceSchedule

19

1934



OPT Features• Lot Sizes

Variable Transfer BatchVariable Process Batch

• Set-upTabular Approach to Dependencies

• ReportsUtilisationStockmanDespatch Daily ForemanRaw Material Requirements

19

1935



OPT Network

RawMaterial

FinishedGoods

Inventory

Components AssembliesCritical Capacity

Restraint

Critical Resource Network

Non Critical Resource Network

19

1936



Drum-Buffer-Rope Analogy

• Drum. The Scheduling Rhythm.

• Rope. "Pulling" Material into the System.

• Buffers. Providing a Time Safety Margin.

Rope BottleneckResource

MaterialLaunched

into System

DrumBuffer

19

1937



Limitations of FCS

• Complex

• Expensive

• Stochastic Process and Set-up Times

• Set-up Time Dependency

• Automatic Rescheduling of a Backlog

Cannot Act as a Substitute for Poor Management

19

1938



FCS - Summary

• FCS - Relatively Old Approach

• Made Popular By OPT

• Simulation of the Manufacturing System

• Can be Employed in Several FormsFull Scheduling SystemShort Interval SchedulingEnhanced RCCP

• Will be Used More Widely in the Future (APS)

19

1939



AlterCo Case Study - Overview

Location East Lancashire

Size 315 Employees

Turnover £15M

Products Alternators

Production 6000 units/wk

Spares Production None

Business Type Make to stock and order

Variety 100 stock types plus specials

19

1940



AlterCo - History

• Problems in the 70's

• Overdues

• Excessive Overtime

• Excessive Inventory

• Shortages

• Computer System Lost Credibility

• Serious Cash Flow Problems

19

1941



AlterCo – Bill of Material

Alternator

Winding

RawMaterial

Shaft

MildSteel

EndCovers (2)

Casting

OtherParts

19

1942



AlterCo – Material Flow

Raw

Material

Stores

Shaft

Winding

End Cover

Other

Component

Stores

Line

Assembly

Finished

Goods

Stores

Despatch

Line

Line

Parts

19

1943



AlterCo – The Initial Response

• Increase Batch Size to Improve Efficiency

• Sequence Work to Minimise Set-ups

• Increase Lead Times

• Increase Capacity in All Areas

The Companies Position was Becoming Serious

19

1944



AlterCo - The Exercise

• Planned to Take Similar Actions

• Set-up a Project Team

• Their Objective - Short Term Improvement

Your Task

• What was the Project Team's Assessment?

• What Action Did they Take?

19

1945



AlterCo – The Real Problems (1)

• Winding was a Bottleneck

• Surprisingly, Other Sections Also Had Overdues

• Other Sections Were Making the Wrong Types

• Manufacture in the Wrong Sequence

• Unmatched Inventory

19

1946



AlterCo – The Real Problems (2)

Sequenced Work

Increase Batches

Increased Capacity

Increased Lead Time

Increased Overdues

Increased Overtime

Increased Stocks

Increased WIP

1

2

3

19

1947



AlterCo – The Short Term Solution

CustomerOrders

MRP

Winding

OtherManufacturing

Sections

19

1948



AlterCo – The Results (1)

• Output of Finished Goods Up

• Most Overdue Jobs Completed First

• Overtime Eliminated Except for Winding

• Reduced Purchasing in Short Term

• WIP/Lead Times Reduced

Efficiency Reduced!!

19

1949



AlterCo – The Results (2)

Overall Overdues

Overall Output

Shaft Output

End Cover Stocks

Shaft Lead Time

Shaft WIP

Shaft Stocks

PerformanceMeasure of

35000 25000

15000 6400

2.5 Wks 1 Wk

40000 32000

7800 5010

6000 8700

21000 13000

January April

But the Project Team Advised Caution

19

1950



AlterCo – The Need for Caution

• Stocks Would Eventually be Consumed

• Non-bottlenecks Would Need to Increase Output

• Only Winding had Any Forward Vision

19

1951



AlterCo – The Long Term Solution

CustomerOrders

MRP

ManufacturingSections

MasterProductionScheduling

CapacityConstraints

(General)

CapacityConstraints(Specific)

19

1952



AlterCo – They All Lived Happily…

Or did they……?

19

1953



Course Book

Systems for Planning & Control in Manufacturing:

Systems and Management for Competitive Manufacture

Professor David K HarrisonDr David J Petty

ISBN 0 7506 49771

X

0000

Documents

Supporting Slides