Outline
2.008
1.
2.
3.
4.
Manufacturing Systems
Manufacturing Systems
Types of Plant Layouts
Production Rates
Design and Operations
2.008 - Spring 2004
2
Manufacture
Market
Research
Conceptual
Design
What is mfg systems?
Design for
Manufacture
Unit
Unit
Manufacturing
Manufacturing
Processes
Processes
Assemblyand
and
Assembly
Joining
Joining
•Welding
•Bolting
•Bonding
•Soldering
Factory,
Systems &
Enterprise
•Machining
•Injection molding
•Casting
•Stamping
•Chemical Vapor
Deposition
2.008 - Spring 2004
How Man, Machine, and
Material Spend Time in the
Factory
Time spectrum of Typical Activities in a
Manufacturing Organization
Seconds
Period
108
Decade
107
Year
106
Month
Week
105
4
Activity
People
Plant design, Machine Selection,
System Simulation
Process design: CAD
Catalogs
Select manufacturing methods
Materials
Hour
Factory Operation
Ship – Receive
Transport Inventory
103
Waste
102
Minute
101
.1
.001
Part handling
Load/Unload
Assembly
“Waste”: waiting for materials,
watching machine running,
producing defects, looking for
tools, fixing machine
breakdowns, producing
unnecessary items, etc.
Second
.01
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Value adde d
Day
104
1
Machines
Value adde d
Valu e adde d
Millisecond
Machine control
CNC – DNC
Adaptive control
Intelligent machines
Process control
5
2.008 - Spring 2004
Waste
“Waste”: transportation, storage,
inspection and rework
Waste
“Waste”: unnecessary
movement of machine, setup
time, machine breakdown,
unproductive maintenance,
producing defective products,
producing products when not
needed, etc.
6
1
Types of Plant Layout
Disruptions/Variation
(Random Events)
• Job Shop
• Machine failure
• Project Shop
• Set-up change
• Flow Line
• Operator absence
• Transfer Line
• Starvation/Blockage
• Cellular System
• Demand change
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7
2.008 - Spring 2004
Job Shop
Project Shop
Raw Material
Machines/Resources are grouped according to the process they
perform
8
A
A
D
D
A
A
D
D
D
D
C
C
C
C
C
C
Machines/Resoues
are brought to and removed from stationary part as required
A
B
A
B
Raw
material/
Ready part
D
C
D
D
Ready part
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Flow Line and Transfer Line
10
Cellular System
Raw Material
Machines/Resources
are grouped in lines
according to the
processes sequence
of part(s)
B
A
Raw Material
Machines/Resources
are grouped
according to the
processes required
for part families
C
A
D
B
D
F
G
F
F
C
D
E
D
E
F
G
A
B
D
F
Ready part
Ready part
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B
11
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2
Production Rates
Production Quantity and Plant Layout
• Case I:
– One machine
– Everything works
Pro ject Shop
Job Shop
M
C ellular System
Flow L i ne
Production rate =
1
10
100
1,000
10,000
100,000
1
Operation time
Quantity
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Production Rates (cont’d)
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14
Production Rates (cont’d)
• Case II:
• Case III:
– One machine
– Machine breaks down (disruption)
– Everything else works
– Many machines
– No machine breaks down
– No buffers
M
M1
MTTF
MTTF
=
MTTF + MTTR MTTR
Efficiency
Production rate =
Operation time
M2
Mi
Mk
Efficiency =
(utilization)
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Production Rates (cont’d)
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Production Rates (cont’d)
• Case IV:
• Case V:
– Many machines (same operation time)
– No machine breaks down
– No buffers
M1
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M2
Mi
– Many machines (same operation time)
– Machine breaks down
– No buffers
Mk
M1
17
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M2
Mi
Mk
18
3
Production Rates (cont’d)
Production Rates (cont’d)
• Case VI:
– Many machines and buffers in between
– Machine breaks down
M1
B1
M2
B2
M3
Mk-1
B
k-1
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• Production rate increases if:
– Increase the rate of the slowest machine
– Reduce the disruptions
– Introduce “buffers”
– Introduce in-process control
Mk
19
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Disruptions
(Random Events)
Waiting
• Machine failure
• Underutilization
• Set-up change
• Idleness
• Operator absence
• Inventory
• Starvation/Blockage
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Inventory/Work-in-Process (WIP)
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Cycle Time and Lead Time
Order
• It costs money
Plant
Supplier
• It gets damaged
Supply
• It becomes obsolete
• It shrinks
Takt time =
• It increases lead time
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Order
23
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Customer
Supply
Daily available time
Daily average demand
24
4
Cycle Time
Cycle Time (cont’d)
“Cycle Time”
• The time a part spends in the system
• Example:
Operation time = 1, One-piece operation
M1
Little’s Law: L = λw
L: average inventory
λ: average production rate
w: average cycle time
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Op1
Op2
M3
M4
M5
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Cycle Time
One-Piece Production
Cycle Time
Batch Production
1.
M2
Production rate = 1
Cycle time = 5
Inventory = 5
2.
Op3
Operation time: 3 minutes
Batch (Lot) size: 1000
Cycle time = 1,000*3 + 1,000*3 + 1,000*3 = 9,000min
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Op1
Op2
Op3
Operation time = 3 minutes
Cycle time = 1,000*3 + 2*3 = 3,006 minutes
27
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Cycle Time and Lead Time
Order
Plant
Supplier
Supply
Takt time =
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Systems Design and Operation
Order
• Cycle time < Lead time
Customer
• Lumpiness
Supply
• Information contents
Daily available time
Daily average demand
29
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5
Lumpy Demand
Wrench A
Wrench C
Wrench B
D 1 1 1 1 1 1
D
P 5
P 15
5
6
6
6
6
6
15
6
D
15
P 10
3
3
3
20
P
25
0
15
25
0
•
•
•
•
•
•
•
•
Wrench D
3
3
3
D
10
7
7
7
P 25
Forging X
D
Typical Design Guidelines
7
7
7
25
Forging Y
0
20
D 35
25
P
50
0
0
35
0
0
50
Steel Z
D
75
0
25 50
0
25
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Leveling
Balancing
Single-piece flow
Low materials handling
Low setup time
Smaller lot size
Low WIP
Faster feedback
32
Plant Operations
• Push (MRP, ERP, etc.) vs. Pull (JIT)
• Batch vs. One-piece
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6