2.008 -Spring 2004 1

2.008

Manufacturing Systems

2.008 -Spring 2004 2

Outline

1. Manufacturing Systems

2. Types of Plant Layouts

3. Production Rates

4. Design and Operations

2.008 -Spring 2004 3

Manufacture

Market Research

Conceptual Design

Design for Manufacture

Unit Manufacturing

ProcessesAssembly

and Joining

Factory, Systems & Enterprise

2.008 -Spring 2004 4

What is mfg systems?

2.008 -Spring 2004 5

Time spectrum of Typical Activities in aManufacturing Organization

Seconds Period Activity

108 Decade

Plant design, Machine Selection,

107 Year System Simulation

Process design: CAD

106 Month Catalogs

Select manufacturing methods

Week

105 Day

Factory Operation

104 Ship-Receive

Hour Transport Inventory

103

102

Minute Part handling

101 Load/Unload

Assembly

1 Second

.1 Machine control

CNC-DNC

.01 Adaptive control

Intelligent machines

.001 Millisecond Process control

2.008 -Spring 2004 6

How Man, Machine, and Material Spend Time in the Factory

People Materials Machines

Value-added

Value-added

Value-added

Waste Waste Waste

“Waste”: transportation, storage, inspect on and rework

"Waste": unnecessary movement of machine, setup time, machine breakdown, unproductive maintenance, producing defective products, producing products when not needed, etc.

"Waste": waiting for materials,watching machine running,producing defects, looking fortools, fixing machinebreakdowns, producingunnecessary items, etc

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Disruptions/Variation(Random Events)

• Machine failure• Set-up change• Operator absence• Starvation/Blockage• Demand change

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Types of Plant Layout

• Job Shop• Project Shop• Flow Line• Transfer Line• Cellular System

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Job Shop

Machines/Resources are grouped according to the process they perform

Raw Material

Ready part

A A

A A

D D

D D

D D

C C

C C

C C

2.008 -Spring 2004 10

Project Shop

Machines/Resources are brought to and removed from stationary part as required

A

A

C

B

B

D

DD

Raw material/

Ready part

2.008 -Spring 2004 11

Flow Line and Transfer Line

Machines/Resources are grouped in lines according to the processes sequence of part(s)

A

A

Raw Material

Ready part

B

B

C

D

D F

F F

G

2.008 -Spring 2004 12

Cellular System

Machines/Resources are grouped according to the processes required for part families

Raw Material

Ready part

B

B

C

E

E

A

D

D

D

F

F

G

2.008 -Spring 2004 13

Production Quantity and Plant Layout

Project Shop

Job Shop

Cellular System

Flow Line

1 10 100 1,000 10,000 100,000

Quantity

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Production Rates

• Case I:– One machine– Everything works

M

time Operation

1rate Production

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Production Rates (cont’d)

• Case II:– One machine– Machine breaks down (disruption)– Everything else works

M

MTTR

MTTF

MTTRMTTF

MTTFEfficiency

on)(utilizati

time Operation

Efficiencyrate Production

2.008 -Spring 2004 16

Production Rates (cont’d)

• Case III:– Many machines– No machine breaks down– No buffers

M1 M2 Mi Mk

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Production Rates (cont’d)

• Case IV:– Many machines (same operation time)– No machine breaks down– No buffers

M1 M2 Mi Mk

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Production Rates (cont’d)

• Case V:– Many machines (same operation time)– Machine breaks down– No buffers

M1 M2 Mi Mk

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Production Rates (cont’d)

• Case VI:– Many machines and buffers in between– Machine breaks down

M1 M2 Mi MkB1 B2 Bk-1Mk-1

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Production Rates (cont’d)

• Production rate increases if:– Increase the rate of the slowest machine– Reduce the disruptions– Introduce “buffers”– Introduce in-process control

2.008 -Spring 2004 21

Disruptions (Random Events)

• Machine failure • Set-up change • Operator absence • Starvation/Blockage

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Waiting

• Underutilization• Idleness • Inventory

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Inventory/Work-in-Process (WIP)

• It costs money • It gets damaged • It becomes obsolete • It shrinks • It increases lead time

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Cycle Time and Lead Time

Order

Supply

Order

Supply

PlantSupplier Customer

demand averageDaily

time availableDaily time Takt

2.008 -Spring 2004 25

Cycle Time

“Cycle Time”

． The time a part spends in the system

Little’s Law: L = λw

L: average inventory

λ: average production rate

w: average cycle time

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Cycle Time (cont’d)

• Example:Operation time = 1, One-piece operation

Production rate = 1

Cycle time = 5

Inventory = 5

M1 M2 M3 M5M4

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Cycle Time Batch Production

1.

Operation time: 3 minutes

Batch (Lot) size: 1000

Cycle time = 1,000*3 + 1,000*3 + 1,000*3 = 9,000min

Op1 Op2 Op3

2.008 -Spring 2004 28

Cycle Time One-Piece Production

2.

Operation time = 3 minutes

Cycle time = 1,000*3 + 2*3 = 3,006 minutes

Op1 Op2 Op3

2.008 -Spring 2004 29

Cycle Time and Lead Time

Order

Supply

Order

Supply

PlantSupplier Customer

demand averageDaily

time availableDaily time Takt

2.008 -Spring 2004 30

Systems Design and Operation

• Cycle time < Lead time

• Lumpiness

• Information contents

2.008 -Spring 2004 31

Lumpy Demand

D 1 1 1 1 1 1

P 5 5

D 6 6 6 6 6 6

P 15 15 15

D 3 3 3 3 3 3

P 10 10

D 7 7 7 7 7 7

P 25 25

D 20 0 15 0 0 20

P 25 25 25

D 35 0 0 35 0 0

P 50 50

D 75 0 25 50 0 25

Wrench A Wrench B Wrench C Wrench D

Forging X Forging Y

Steel Z

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Typical Design Guidelines

• Leveling • Balancing • Single-piece flow • Low materials handling • Low setup time • Smaller lot size • Low WIP • Faster feedback

2.008 -Spring 2004 33

Plant Operations

• Push (MRP, ERP, etc.) vs. Pull (JIT)• Batch vs. One-piece