04/22/23 ISE (Course #) 1

Flexible Work Systems

Chapters 9 and 10

Week 5 and 6, Part I

04/22/23 ISE (Course #) 2

Typical Case Model

ValueStream

Mapping

FlexibleWork

Systems

5S

StandardWork

SMED

Jidoka

TotalProductive

Maintenance

JIT

Heijunka

Goal: Highest Quality, Lowest Cost, Shortest Leadtime

04/22/23 ISE (Course #) 3

Overview

Group Technology – groups products into families

Focused Factories – workers and equipment produce one family of products

Cellular Manufacturing – performing the necessary operations to make all or part of a product in a workcell

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Definitions

Group TechnologyUsed to identify similarities among different products and to group them into families

Focused FactoriesThe same workers and equipment produce a specific family of products

Cellular ManufacturingPerforming all of the necessary operations to make a part, component, subassembly, or finished product in a workcell

04/22/23 ISE (Course #) 5

Ways of Doing Work

Quantity Produced / Cost per unit

Volume

Mass production (repetitive)

Batch production

Project

Continuous

Job shop

04/22/23 ISE (Course #) 6

Types of Facilities Layouts

Fixed-Position Layout (Project Shop) Product stays in one place Labor and materials moved to the product (e.g. buildings, race cars, aircraft)

Process Layout (Job Shop/Batch Shop) Similar operations clustered into functional areas Jobs routed through the areas

Product Layout (Continuous Flow) Only one product is produced on the line Used for continuous repetitive production

04/22/23 ISE (Course #) 7

Wastes in a Process Layout

Travel between operations

Wasted space

Delays from batch processing

Nicholas, 1998

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Benefits of a Process Layout

Almost no travel time between processes

Smaller batches reduce wasted space

Fewer delays because of the small batches

Nicholas, 1998

04/22/23 ISE (Course #) 9

Hybrid Layouts

Cellular layouts Group machines into machining cells

Flexible manufacturing systems Automated machining & material handling

systems

Mixed-model assembly lines Produce variety of models on one line

R. O. Buchal, 2000

University of Western Ontario

04/22/23 ISE (Course #) 10

Traditional View - Tradeoffs

Conventional manufacturers select a process type by making trade-offs between efficiency and variety

Lean producers find ways to get both

Group technology and focused factories are one way to achieve this

R. O. Buchal, 2000

University of Western Ontario

04/22/23 ISE (Course #) 11

Group Technology

Used to group products into families Similar design among the products Similar processing used

Product Coding and Classification Schemes Hierarchical (Monocode) Structure Chain (Polycode) Structure Hybrid Structure

Product Families and Focused Factories

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Hierarchical Structures

Interpreted as an inverted-tree hierarchy

Uses a code to represent each part

Nicholas, 1998

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Chain Structures

Also uses a code to represent each part

Each digit has its own unique meaning

Digit Position

1 Class of part

2 External shape

3 Internal machining

4 Surface machining

5 Gear teeth forming

Interpretation

3 = Turning part with L/D > 2

7 = Cone

3 = Functional grooves

5 = External planed surface

7 = With bevel gear teethNicholas, 1998

04/22/23 ISE (Course #) 14

Product Families

Group products into families Based on GT product codes

If enough demand for a product family… Create a focused factory for the family

Focused factories are not product layouts The factory can create all products in the family Product layout is specifically for one product

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Focused Factories

Focused flow lines When parts in family have nearly the same

process sequence and processing times

Workcells More flexible, when parts have greater differences

Focused workcentres Used when it’s not practical to rearrange machines Individual machines are dedicated to particular families

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Product and Machine Groups

Coding and classification Use GT codes

Cluster analysis Grouping achieved by visual inspection of

process plans

Production Flow Analysis (PFA) Similar to cluster analysis Uses matrix methods to find clusters

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Original Process Layout

12

1

2

3

4

5

6 7

8

9

10

11

A B C Raw materials

Assembly

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Part Routing Matrix

Parts Machines1 2 3 4 5 6 7 8 9 10 11 12

A X X X X X

B X X X X

C X X X

D X X X X X

E X X X

F X X X

G X X X X

H X X X

04/22/23 ISE (Course #) 19

Reordered to Highlight Cells

Parts Machines1 2 4 8 10 3 6 9 5 7 11 12

A X X X X X

D X X X X X

F X X X

C X X X

G X X X X

B X X X X

H X X X

E X X X

04/22/23 ISE (Course #) 20

Cellular Layout Solution

12

12 3

4

5

6

7

8 910

11

A BCRaw materials

Cell1 Cell 2 Cell 3

Assembly

04/22/23 ISE (Course #) 21

Advantages of Focused Factories

70 – 95% reduction in WIP65 – 80% reduction in setup times70 – 90% reduction in lead time75 – 90% reduction in handling20 – 56% reduction in factory space96% reduction of late ordersBetter use of human resourcesEasier to controlEasier to automate

04/22/23 ISE (Course #) 22

Disadvantages of Focused Factories

Inadequate part families

Poorly balanced cells and low machine utilization

Expanded training and scheduling of workers

Increased capital investment

04/22/23 ISE (Course #) 23

Cellular Manufacturing

Manufacturing cell concepts

Workcell design Worker Issues Equipment Issues

Implementation

Getting Started

04/22/23 ISE (Course #) 24

Manufacturing cells

Concepts Workstations are located closely together Are commonly U-shaped Divided subcells vs. Rabbit chase (cell output)

Applications Can produce an entire product, or a

subassembly Can produce multiple product families Can be used to link other workcells and

subcells

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Manufacturing Cell with One Worker

Enter

Exit

Key: Product routeWorker route

Machines

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Manufacturing Cell with 3 Workers

Enter

Worker 1

Worker 2Worker

3

Exit

Key: Product routeWorker route

Machines

04/22/23 ISE (Course #) 27

Cells are Flexible

Flexible labor multi-skilled, adaptable operators the number of operators can be changed to

change capacity

Flexible equipment a variety of products are produced on the same

equipment this requires multifunctional machines

Achievable with basic technology!

04/22/23 ISE (Course #) 28

Linked Cells and Subcells

A manufacturing cell usually has less than 10 stations, and usually each worker tends more than one station

Cell output (capacity) can be varied by adding or removing workers

For complex products, multiple cells can be linked through kanbans or other methods

04/22/23 ISE (Course #) 29

Linked Manufacturing Cells

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Workcell Design

Two main types of cells:

Assembly Hard to automate Mostly manual

Machining Simpler, easier to automate

04/22/23 ISE (Course #) 31

Takt and Cycle Times

Cycle time is time interval between completed parts coming from the cell

Takt time is determined by demand (book calls it required cycle time)

Actual cycle time is determined by cell capacity

Actual cycle time should be close to takt time

04/22/23 ISE (Course #) 32

Takt Time

Demand Required

Available Time TimeTakt

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Assembly Cycle Times

Walk times timesOperationaCT

aCT

available Timecapacity Cell

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Increasing Capacity

Add workers and divide cell into subcells

Limit: one worker at each station

Overall cycle time is equal to cycle time of slowest subcell

Alternative: rabbit chase

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Machining Workcells

Usually use automatic, single-cycle machines

Worker tasks: Unload finished part Setup if necessary Load new part Start machine (it runs and stops automatically)

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Machining Cell Cycle Time

Walk times Task timesWorker CT

Cell CT (one worker) = max(Worker CT, longest machine CT)

Machine CT = unload + setup + load + processing time

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Increasing Capacity

Again, cell capacity can be increased by adding workers until machine capacity is reachedFor flexibility, cells should be designed so machines have lots of excess capacityAdditional machines can be added if necessaryThis is most feasible if cost of machine time is low (simple, inexpensive machines)

04/22/23 ISE (Course #) 38

Single Piece Flow

If setup time is very short, products can be made in any order in batch sizes of 1

Since parts are all similar, setup times of a few seconds are achievable

04/22/23 ISE (Course #) 39

Worker Issues

Workers must be able to operate a range of equipment and perform a variety of tasks

Cross Functional Training

Workers are reassigned to different cells as required by changing demand

04/22/23 ISE (Course #) 40

Equipment Issues

Lots of inexpensive machines are better than a few expensive ones They can be allocated to different cells They are easy to relocate Running them at low utilization is not a

concern

04/22/23 ISE (Course #) 41

Manufacturing Cell Automation

Pros Faster Increases repeatability Some cells can be well suited to automation

Cons Expensive Reduces flexibility

04/22/23 ISE (Course #) 42

Implementing Cellular Manufacturing

Use MRP-type planning and control system Typically are found in organizations

implementing workcells Eventually will move into a Kanban control

system with MRP-type planning system

Typically want to replace the traditional incentive plan with a group-based plan Emphasizes teamwork Improves morale

04/22/23 ISE (Course #) 43

Employees

Need to cross-functionally train workers

Need to get buy-in from employees at all levels of the company or implementation will not work

This MUST begin with upper management

04/22/23 ISE (Course #) 44

Getting Started

Initial plan for workcells conducted by multifunctional steering committeeA core team should be formed for each workcell – detailed cell design and final implementationImplement with one or two pilot cells Commonly takes about 6 months Linked workcells begin downstream and works

backward

04/22/23 ISE (Course #) 45

Typical Case Model

ValueStream

Mapping

FlexibleWork

Systems

5S

StandardWork

SMED

Jidoka

TotalProductive

Maintenance

JIT

Heijunka

Goal: Highest Quality, Lowest Cost, Shortest Leadtime