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
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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
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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
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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
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Cellular Layout Solution
12
12 3
4
5
6
7
8 910
11
A BCRaw materials
Cell1 Cell 2 Cell 3
Assembly
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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
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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
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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
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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!
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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
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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
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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
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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
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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
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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
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Manufacturing Cell Automation
Pros Faster Increases repeatability Some cells can be well suited to automation
Cons Expensive Reduces flexibility
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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
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