Supporting Slides

1
Supporting Slides
X
Systems for Planning Control in
Manufacturing Systems and Management for
Competitive Manufacture
Professor David K Harrison Glasgow Caledonian
University Dr David J Petty The University of
Manchester Institute of Science and Technology
ISBN 0 7506 49771
0000
2
Finite Capacity Scheduling (FCS)
19

• 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

1901
3
MRP Limitations
19
Job
A
Quantity
100
Due Date
07/10
Total Time to Manufacture A 11.33Hrs
Operation
10
Work Centre
001
Set Time
60 Mins
Total Time to Manufacture B 12.17Hrs
Unit Time
2 Mins
20
Work Centre
002
Set Time
120 Mins
Unit Time
3 Mins
Job
B
Quantity
100
What is the Best Sequence for Manufacture?
Due Date
07/10
Operation
10
Work Centre
001
Set Time
120 Mins
Unit Time
4 Mins
20
Work Centre
002
Set Time
60 Mins
Unit Time
1.5 Mins
MRP Assumptions
Work
Work
Centre
Centre
Fixed Lot Sizes
001
002
Fixed Lead Times
1902
4
Finite and Infinite Scheduling
19
MRP - Assumes Dominant Queuing Time
Start
Start
Due
Due
Now
Now
Date
Date
Date
Date
Lead Time
1903
5
Data 1 Workcentres
19
Efficiency
2 Shift
8 Hours
1 M/C
Forging
50/Hr
Factor 90
Pattern
per Shift
in Group
Press
1029
Efficiency
2 Shift
8 Hours
1 M/C
40/Hr
Lathe
Factor 90
Pattern
per Shift
in Group
1013
Efficiency
2 Shift
8 Hours
1 M/C
Vertical
45/Hr
Factor 90
Pattern
per Shift
in Group
Mill
1019
Efficiency
2 Shift
8 Hours
1 M/C
25/Hr
Drill
Factor 90
Pattern
per Shift
in Group
1023
1904
6
Data 2 - Routings
19
Item Number GDS8975T
Operation 10
Operation 20
Operation 30
Operation 40
W/C 1029
W/C 1013
W/C 1019
W/C 1023
Ts 90 Mins
Ts 45 Mins
Ts 80 Mins
Ts 90 Mins
Tp 3 Mins
Tp 2 Mins
Tp 2 Mins
Tp 2 Mins
Tm 240 Mins
Tm 240 Mins
Tm 240 Mins
Tm 240 Mins
Tq 480 Mins
Tq 480 Mins
Tq 480 Mins
Tq 480 Mins
Mill slots and inlet
Drill 15 holes,
Turn complete to
Set press to 15T.
pockets to
evenly spaced.
drawing. Use NC
drawing. Use NC
tape number
tape 1264-9888.
1938-0484.
1905
7
Example Routing
19
Job 1
Job 2
Job 3
Job 4
Job 5
Job 6
Op. Operation R Resource
Operation 4 on Resource 6
1906
8
Infinite Scheduling - Example
19
Start Date
Due Date
Op 1.
Op 2.
Op 3.
Op 4.
Job 1
Job 1
Job 2
Job 2
Job 3
Job 3
Job 4
Job 4
Job 5
Job 6
Job 5
Job 6
Lead Time
Load Hrs
Load Hrs
Load Hrs
Load Hrs
Load Hrs
Load Hrs
R1
R2
R3
R4
R5
R6
Cap.
Cap.
Cap.
Cap.
Cap.
Cap.
R1
Overload
Overload
R4
Op 1.
5
6
7
8
5
6
7
8
5
6
7
8
5
6
7
8
5
6
7
8
5
6
7
8
Time (Days)
Time (Days)
Time (Days)
Time (Days)
Time (Days)
Time (Days)
1907
9
Infinite Scheduling - Key Points
19

• Jobs Never Late by Definition
• Problems Shown by Overloads
• Does not Provide Solutions
• Called CRP with MRPII/ERP

1908
10
Finite Capacity Scheduling (1)
19

• Different Methods Available
• Computers Commonly Used
• Manual Methods (e.g. Gantt Charts) Available

• Determine Priority Sequence
• Load Jobs Progressively
• Optimise Schedule

General Approach
1909
11
Finite Capacity Scheduling (2)
19
Job 1
Job 2
Job 3
Job 4
Job 5
Job 6
Time
R1
R2
R3
R4
R5
R6
1910
12
Finite Capacity Scheduling (3)
19
Job 1
Job 2
Job 3
Job 4
Job 5
Job 6
Time
R1
R2
R3
R4
R5
R6
1911
13
Finite Capacity Scheduling (4)
19
Job 1
Job 2
Job 3
Job 4
Job 5
Job 6
Time
R1
R2
R3
R4
R5
R6
1912
14
Finite Capacity Scheduling (5)
19
Job 1
Job 2
Job 3
Job 4
Job 5
Job 6
Time
R1
R2
R3
R4
R5
R6
1913
15
Finite Scheduling - Key Points
19

• Resources Never Overloaded
• Problems Shown by Lateness
• Ignores Subjective Factors

1914
16
Schedule Optimisation
19
Time
R1
R2
R3
R4
R5
R6
Idle
Queue

• Is this the Best Schedule?
• Objective Functions
• Permutations mn

• Minimum Makespan
• Minimum Tardiness
• Maximum Profit

1915
17
Johnsons Algorithm
19
Which Sequence Will Minimise Makespan?
Machine 1
Machine 2
Queue
Yes
No
Machine
Job
Time (1)
Time (2)
Seq.
6
D
6
A
7
5
A
B
4
4
11
H
C
5
5
Yes
4
I
4
D
8
9
E
9
E
12
10
F
10
F
13
No
13
G
G
9
9
7
J
7
H
10
8
C
8
I
9
8
B
J
6
6
1916
18
Work-to-Lists
19
MRP Due
Back Scheduling

• Issued to Each Work Centre
• Means of Detailed Control
• Issued Daily

Date
Op 40
Logic
Op 30
Op 20
Op 10
MRP Start
Date
Prioritisation
Rules
Work Centre
Centre Lathes
Issue Date
17/04/05
0290

Part
Operation Due
Next Work
Previous
Order Due
Work Order
Quantity
Number
Number
Due Date
Centre
Work Centre
Date
3000167
GOS1365
06/05/05
18/04/05
0360
0370
1000
3000369
GDS1987
07/05/05
18/04/05
0360
0370
1000
3000258
PFF1888
12/05/05
18/04/05
0380
0410
1000
3000198
TDS3687
16/05/05
18/04/05
0360
0370
1000
3000153
TDS9637
17/05/05
19/04/05
0360
0420
1000
1917
19
Prioritisation and Sequencing 1
19
m
n
Time Available (T )
Today
Due
a

• SPT
• EDD
• LPT

• Static Rules

1918
20
Prioritisation and Sequencing 2
19
m
n
Time Available (T )
Today
Due
a

• Dynamic Rules

• FIFO
• Cr
• LS
• LSPRO

1919
21
Prioritisation and Sequencing 3
19
m
n
Time Available (T )
Today
Due
a

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

• Informal Rules

1920
22
Prioritisation and Sequencing 4
19
Priority List
A B C D E F G H I J
Selection Window
This Approach is a Compromise Between Set-Up Time
and Manufacturing in a sequence related to
Customer Requirements
1921
23
Shop Floor Feedback
19

• Completions
• Time Required
• Process Data
• Labour Productivity M/C Efficiency
• M/C Breakdowns
• Scrap
• Rework
• Defect Analysis

lt102394gt
Transducer
Smart
Tag
Controller
Hand Held
Computer
Application
Direct

• Remote Entry
• Shop Floor Terminals
• Data Collection

Software
Interface
1922
24
Short Interval Scheduling (SIS)
19
Business Planning
Sales and Operations Planning
Master Production Scheduling
Upload
Download
Interface
Material Requirements Planning
Capacity Requirements Planning
SIS System

• Hybrid Approach
• Simulation
• What-if Analysis
• Operational
• Rough Cut Capacity Planning
• Cannot Cope with a Heavily Overloaded Situation

No
Realistic
Yes
Shop Floor Control
Purchasing
1923
25
Rough Cut Capacity Planning 1
19
Objective to Check that the MPS is Valid
MPS
Product Load Profile
Resources
RCCP
Load Per Unit

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

Resource Load Profile
Time Before Due Date
Load
Capacity
Time
1924
26
Rough Cut Capacity Planning 2
19

• 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

1925
27
RCCP vs CRP
19
RCCP
CRP
Detailed evaluation of load
Estimated Load on critical
Definition
based at work centre level
resources based on MPS
Calculation based on all
Use of MPS and product
Method
works orders
load profiles
As required
Following each MRP run -
Frequency
typically once a week
1. Post-MRP analysis
1. Pre-MRP evaluation of MPS
Objective
2. Determining bottlenecks
2. Operational planning
Detailed
Aggregate
Precision
MPS and product load profiles
Works orders, work centres,
Data
routings and works order status
Fast
Typically longer than MRP
Speed
Virtually all users of formal
A minority of users
Use
manufacturing management Systems
1926
28
Disadvantages of CRP
19

• Data Hungry
• Need for Feedback
• Timing of Information

1927
29
OPT Background
19

• Doubts Over MRPII
• Developed by Dr EM Goldratt in the 1970s.
• OPT has Two Elements
• Philosophical
• Finite Scheduling Algorithm

1928
30
OPT Principles
19
"The Goal" - To Make Money
OPT Emphasises the Importance of Bottlenecks. A
Bottleneck is any Resource where Capacity is less
than Load
1929
31
Ten Rules of OPT
19
1. Balance flow, not capacity. 2. The level of
utilisation of a non-bottleneck is determined not
by its 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. Bottlen
ecks govern both throughput and
inventory. 7. The transfer batch may not, and
many times should not, be equal to 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.
1930
32
Process and Transfer Batches - 1
19
Standard Case Process Batch and Transfer Batch
the Same Size
Operation 10
Operation 20
Operation 30
Operation 40
1931
33
Process and Transfer Batches - 2
19
Process Batch 9 Transfer Batch 9
Process
Transfer
Process
1932
34
Process and Transfer Batches - 3
19
Process Batch 9 Transfer Batch 3
Process
Transfer
Transfer
Transfer
Process

• Second Process Starts Earlier
• WIP is Reduced
• Lead Time is Reduced
• Increased Material Handling

1933
35
OPT Mechanics
19
Routing
Critical
OPT
Resource
OPT
Network
Schedule
Initial
SPLIT
SERVE
BUILDNET
Analysis
Non-Critical
SERVE
SERVE
Resource
Network
Schedule
BOM
1934
36
OPT Features
19

• Lot Sizes
• Variable Transfer Batch
• Variable Process Batch
• Set-up
• Tabular Approach to Dependencies
• Reports
• Utilisation
• Stockman
• Despatch
• Daily Foreman
• Raw Material Requirements

1935
37
OPT Network
19
Raw Material
Finished Goods Inventory
Components
Assemblies
Critical Capacity Restraint
1936
38
Drum-Buffer-Rope Analogy
19
Buffer
Drum
Material Launched into System
Rope
Bottleneck Resource

• Drum. The Scheduling Rhythm.
• Rope. "Pulling" Material into the System.
• Buffers. Providing a Time Safety Margin.

1937
39
Limitations of FCS
19

• 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
1938
40
FCS - Summary
19

• FCS - Relatively Old Approach
• Made Popular By OPT
• Simulation of the Manufacturing System
• Can be Employed in Several Forms
• Full Scheduling System
• Short Interval Scheduling
• Enhanced RCCP
• Will be Used More Widely in the Future (APS)

1939
41
AlterCo Case Study - Overview
19
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
1940
42
AlterCo - History
19

• Problems in the 70's
• Overdues
• Excessive Overtime
• Excessive Inventory
• Shortages
• Computer System Lost Credibility
• Serious Cash Flow Problems

1941
43
AlterCo Bill of Material
19
1942
44
AlterCo Material Flow
19
Shaft
Line
Winding
Line
Raw
Finished
Component
Material
Assembly
Goods
Stores
Stores
Stores
End Cover
Line
Other
Parts
Despatch
1943
45
AlterCo The Initial Response
19
The Companies Position was Becoming Serious

• Increase Batch Size to Improve Efficiency
• Sequence Work to Minimise Set-ups
• Increase Lead Times
• Increase Capacity in All Areas

1944
46
AlterCo - The Exercise
19

• 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?

1945
47
AlterCo The Real Problems (1)
19

• Winding was a Bottleneck
• Surprisingly, Other Sections Also Had Overdues
• Other Sections Were Making the Wrong Types
• Manufacture in the Wrong Sequence
• Unmatched Inventory

1946
48
AlterCo The Real Problems (2)
19
1
Sequenced Work
Increased Overdues
Increase Batches
2
Increased Overtime
Increased Capacity
Increased Stocks
3
Increased Lead Time
Increased WIP
1947
49
AlterCo The Short Term Solution
19
MRP
Winding
1948
50
AlterCo The Results (1)
19

• 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!!
1949
51
AlterCo The Results (2)
19
Measure of
Performance
January
April
Shaft Stocks
35000
25000
Shaft WIP
15000
6400
Shaft Lead Time
2.5 Wks
1 Wk
End Cover Stocks
40000
32000
Shaft Output
7800
5010
Overall Output
6000
8700
Overall Overdues
21000
13000
But the Project Team Advised Caution
1950
52
AlterCo The Need for Caution
19

• Stocks Would Eventually be Consumed
• Non-bottlenecks Would Need to Increase Output
• Only Winding had Any Forward Vision

1951
53
AlterCo The Long Term Solution
19
MRP
1952
54
AlterCo They All Lived Happily
19
Or did they?
1953
55
Course Book
X
Systems for Planning Control in
Manufacturing Systems and Management for
Competitive Manufacture Professor David K
Harrison Dr David J Petty ISBN 0 7506 49771
0000