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8/11/2019 Cell Manufacturing System
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Cell ManufacturingSystems (CMS)Jaudiel Arredondo
Moisés DíazCarlos Hurtado
Francisco Leyva
José Manuel Montoya
Will Palacios
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Topics
What is Cell Manufacturing System?
CMS and Group Technology
Clustering Techniques: the Fundamental Issue in Cell Development
Clustering Methods: Computing Similarity Coefficients
Clustering Methods: Rank order Clustering
Alternative means to Develop Cells/Families
Life in the Cell – Working with Family Fixturing Ideas
Conclusion
8/11/2019 Cell Manufacturing System
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What is Cell Manufacturing
System?
Cellular Manufacturing (CM) has been emergedas a strong approach for improving operations in
batch and job shop environments. In cellularmanufacturing, Group Technology is used toform part families based on similar processingrequirements. Parts and machines are then
grouped together based on sequential orsimultaneous techniques.
8/11/2019 Cell Manufacturing System
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What is Cell Manufacturing
System?
This approach results in cells where machinesare located in relative proximity based on
processing requirements rather than similarfunctional aspects. Decision-making andaccountability are more locally focused, oftenresulting in quality and productivity
improvements.
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Examining a Cell in the CMS:
Notice the‘multi-functional’
workers – thisteam is
responsible forall productionwithin their cell
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Topics
What is Cell Manufacturing System?
CMS and Group Technology
Clustering Techniques: the Fundamental Issue in Cell Development
Clustering Methods: Computing Similarity Coefficients
Clustering Methods: Rank order Clustering
Alternative means to Develop Cells/Families
Life in the Cell – Working with Family Fixturing Ideas
Conclusion
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CMS and Group Technology (GT)
• CMS layout are based on recognizing similarities inproducts – similarities in geometry, size, materials andprocessing requirements.
• This similar products are collected – “Grouped” insteadof being treated as individuals.• Leads to product families that visit similar equipment
and populate their „cells‟ production schedule.• Simpler setups like in a Job shop can follow and the
workers become multifunctional and responsible for allaspects of a product – and its quality.• Cells can be scheduled to produce synchronously
bringing the various sub-assemblies in as needed at finalassembly with greater variety built in.
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CMS and Group Technology (GT)
The Job shop can beconverted into Cell
Manufacturing Systemsby applying GroupTechnology which findscompatible families of
parts.Cells can then bedesigned to process
families of parts.
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CMS and Group Technology (GT)
NOTE: Step 1 is CMS – a fundamental action in LEAN Manufacturing
BuildingtheFACTORYWith AFUTURE
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CMS and Group Technology (GT)
STEP1: Selectparts to be
STEP2: SelectMachines
STEP3: ReviseParts
STEP4: Revise Machines
STEP2: Relocate Machines
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Benefits of GT and CMS (Companies
Reporting):• 52% Report reduction in new part design
• 10% Report reduction in # of new drawings thrustandardization
• 30% Report reduction in new shop drawings
• 60% Report reduction in IE time
• 20% Report reduction in floor space
• 45% Report reduced scrap• 80% Report reduced production and quality costs
• 69% Report reduced set-up time (cost)
Note: ‘Reported’ by companies in a survey of adopters of GT
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Benefits of GT and CMS (Companies
Reporting):• 70% Report reduced throughput time (even more report better
predictability of delivery)
• 82% Report reduced numbers of overdue orders
• 42% Report reduced raw-materials inventory
• 62% Report reduced WIP
• 60% Report reduced finished goods inventory
• 33% Report increased employee output/time unit (productivityimprovement)
Note: ‘Reported’ by companies in a survey of adopters of GT
8/11/2019 Cell Manufacturing System
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Topics
What is Cell Manufacturing System?
CMS and Group Technology
Clustering Techniques: the Fundamental Issue in Cell Development
Clustering Methods: Computing Similarity Coefficients
Clustering Methods: Rank order Clustering
Alternative means to Develop Cells/Families
Life in the Cell – Working with Family Fixturing Ideas
Conclusion
8/11/2019 Cell Manufacturing System
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Clustering Techniques: the Fundamental
Issue in Cell Development
• We cluster parts to build part families• Part Families visit cells
• Part Families share set-up ideas andequipment (Family Fixtures)
• Part Families follow the same (or similar)
process routing• These are the ideas and activities that offerreported benefits
8/11/2019 Cell Manufacturing System
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Clustering Techniques: the Fundamental
Issue in Cell Development• We cluster Machines to build cells:
• Cells lead to Flow Mathematics
• Cells contain all equipment needed to produce a partfamily
• Cells allow development of Multi-functional workers
• Cells hold work teams responsible for production andquality “They Empower” the workers
• Empowered to set internal schedules• Empowered to assign tasks
• Empowered to train and rotate jobs
• Etc, etc, etc
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8/11/2019 Cell Manufacturing System
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Clustering Methods
•Using Process Similarity methods:
•Create Machine – Part Matrices•Compute machine „pairwise‟Similarity Coefficient comparisons:
:
is # of parts (in matrix) visiting
both machines of the pair
is # of parts visiting one but not both machines
ij
jj x
ijij
ij jj
here
x
xS x x
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Part ‘Number’
M a c h
i n eI D
X 1 2 3 4 5 6
A 1 1
B 1 1
C 1 1
D 1 1 1
E 1 1 1
Example:
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Computing Similarity Coefficients:
• Total Number is:• [(N-1)N]/2 = [(5-1)5]/2 = 10
• For 25 machines (typical number in a small JobShop): 300 Sij‟s
• Here they are:1
.33
1 20
00 4
2.67
2 1
AB
AC
AD
S
S
S
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Continuing:
00
0 5
0
00 4
2.67
2 1
00
0 5
00
0 5
2.67
2 1
0
00 6
AE
BC
BD
BE
CD
CE
DE
S
S
S
S
S
S
S
• Here, if the similaritycoefficient is .33 considerclustering
• This criteria means clustering:• A&D, A&B, B&D
• C & E
• Declustering:• A&C, A&E, B&C, B&E and C&D, D&E
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8/11/2019 Cell Manufacturing System
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Summarizing:
• Make Machine/Part Matrix
• Compute Similarity Coefficients
• Cluster Machines with positive ( .33) Sij‟s • Determine Part Families for the clusters (cells)
• Decide if machine replication is cost effective
• Re-layout facility and Cross Train workforce• Start counting your new found cash
• Court customers to grow part families on Cell-by-Cellbasis
8/11/2019 Cell Manufacturing System
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Topics
What is Cell Manufacturing System?
CMS and Group Technology
Clustering Techniques: the Fundamental Issue in Cell Development
Clustering Methods: Computing Similarity Coefficients
Clustering Methods: Rank order Clustering
Alternative means to Develop Cells/Families
Life in the Cell – Working with Family Fixturing Ideas
Conclusion
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Other Clustering Methods:
• Rank order Clustering• This method automates the cluster study by computing
Binary weights from a machine – part matrix
• It orders parts and machine cells „automatically‟ bystructuring and computing the matrix with binary weights
• It implies a computer algorithm for solving the clusteringproblem
• It may not solve if machines are needed by more than onefamily – forces intelligence in application and hand scanningafter several ordering iterations
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8/11/2019 Cell Manufacturing System
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Lets try it with our earlier
problem:
Part ‘Number’
M a c h i n
eI D
X 1 2 3 4 5 6 A 1 1
B 1 1
C 1 1D 1 1 1
E 1 1 1
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Step 1:
Part Numbers D. Equiv Rank
M a c h i n eI D
1 2 3 4 5 6
B. Wt: 25 24 23 22 21 20
A 1 1 23+21 = 10 5
B 1 1 24+23 = 24 4
C 1 1 25+22=36 2
D 1 1 124+23+21
= 263
E 1 1 125+22+20=
371
Step 2: Must Reorder!
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Step 3:
Part Number
B.WT.
1 2 3 4 5 6
M a c h i n e
I D
E 24 1 1 1
C 23 1 1
D 22 1 1 1
B 21 1 1
A 20 1 1
D.Equiv
24+23 = 24
22+21
= 622+21
+20=724+23
=2422+20
=524=16
Rank 1 5 4 2 6 3
Step 4: Must Reorder
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Back at Step 1:
Part Number D. Eqv Rank
1 4 6 3 2 5
B Wt: 25 24 23 22 21 20
M a c h i n eI D
E 1 1 125+24+23=56
1
C 1 125+24=48
2
D 1 1 1 22+21+20 = 7
3
B 1 1 22+21=6 4
A 1 1 22+20=5 5
Order stays the same: STOP!
GreatCluster
Result!
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8/11/2019 Cell Manufacturing System
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Topics
What is Cell Manufacturing System?
CMS and Group Technology
Clustering Techniques: the Fundamental Issue in Cell Development
Clustering Methods: Computing Similarity Coefficients
Clustering Methods: Rank order Clustering
Alternative means to Develop Cells/Families
Life in the Cell – Working with Family Fixturing Ideas
Conclusion
8/11/2019 Cell Manufacturing System
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8/11/2019 Cell Manufacturing System
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Examining Opitz Code:
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Alternative means to Develop
Cells/Families:• They can be company specific
• If so, they are typically hierarchical and
list important characteristics of thepart/process mix, physical characteristicslike size, geometric features, or material,
etc.• Since they are specific they tend to bemore accurate in building part families
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Alternative means to Develop
Cells/Families:• Using GT Classification and coding systems,parts are coded by experts at the company
• The newly coded part is used to searchexisting production databases for similarlycoded products
• The new part is assigned to the family it mostclosely matches
• Its routing is thus set and only minor variationneeds to be considered
• Using specific digits, a company can targetmarketing in certain areas of their productmix
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Alternative means to Develop
Cells/Families:• In a greenfield shop, managers candevelop facility designs (in the form of
reasonable cells) by selecting reasonable„seed‟ parts as suggested by their GT C&Csystem
• These „seeds‟ can be used to build routers
and, hence appropriate machine clusters• Using GT C&C systems, process clustersevolve from parts as opposed to clustering
evolving by process
8/11/2019 Cell Manufacturing System
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Topics
What is Cell Manufacturing System?
CMS and Group Technology
Clustering Techniques: the Fundamental Issue in Cell Development
Clustering Methods: Computing Similarity Coefficients
Clustering Methods: Rank order Clustering
Alternative means to Develop Cells/Families
Life in the Cell – Working with Family Fixturing Ideas
Conclusion
8/11/2019 Cell Manufacturing System
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Life in the Cell – Working with
Family Fixturing IdeasFixturing is a means to speed up part loadingand increase accuracy of machine and mfg.processes
These are tools that:• Locate the work for geometric control• May also provide a means to guide the toolingused to perform the operations (“Jigs”)
• Before being used these tool must beaccurately placed on the machine – often atime consuming task since their placementtolerance must be 10x better than parttolerance!
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Life in the Cell – Working with
Family Fixturing Ideas• In CMS, it is often possible to build FamilyFixtures
• These are fixtures that can be shared amongall the parts in the family (because they aresimilar geometrically and by mfg. process) thusreducing time to set-up any part in the family
• The Family Fixture is generic and may (likely)require the addition of specific change piecesfor different members of the family – but
definitely not different fixtures.
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Life in the Cell – Working with
Family Fixturing Ideas• Example of Cost Savings:
• Shop cost is $50/hour
• Hand setup is 2 minutes/piece (lot is 400 parts)
• Setup on Fixture is 0.03 min/part
• Saving of 1.97 min = .033 hr = $1.64/part
• If machine takes 5 minutes/part, Production rateincreases from 8.57 parts/hour to 11.93 parts/hr almost
a 40% increase!• The company would invest in Fixturing tools if the cost
of a fixture applied to a given part over the life of thetooling and part production is less than the $1.64savings from reduced setup times
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Life in the Cell – Working with
Family Fixturing Ideas• Conventional fixturing means a separatefixture for each part made
• Family fixturing means a separate fixturefor each family made (but severaladaptors for individuals in the family)
• Typically, FFixtures cost more thanconventional fixtures – so lets do a costanalysis
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Conventional Fixturing
• Facility Tool Costs:
1
1
leads to unit tooling cost/part:
i
i
i
tools
P
tools w
i
w d m f i h
P
w
iu
where
C C
C C C C C C
C
C
P n
P = number of partsneeding tooling
Cd is design cost;Cm is material cost;
Cf is fabrication cost;Ci is inventory cost;Ch is handling cost
n = lifetime number of
parts to be made (est.)
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Family Fixturing:
• Cell Tooling Cost:
1( )
leads to unit tool cost/part:
cost of adaptor
Q
tools FF a
i
a
FF d m f i h
tool u
C C C i
C
C C C C C C
C C
Q n
Q = number of parts inFamily
Cd is design cost;Cm is material cost;
Cf is fabrication cost;Ci is inventory cost;Ch is handling cost
n = lifetime number of each part
in family to be made (est.)
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Lets do an Example:
Conventional GT Ideas
Main Tool $500 $1000
# F. Required 1/part 1 for family
Cost Adaptor NA $100
No. Adaptors Req’r NA .85/part
Typical Order Size 400 400
Typical Batch/lifetime 3batch/yr/3yrs = 3600 3batch/yr/3yrs = 3600
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Costs of tooling – a function of the
number of parts in a family!No. Parts C. Tools Unit Cost GT Tools Unit Cost
1 $500 500/3600 = .139 $1085*1085/3600 =.301 (.278)
2 $1000 1000/7200=.139 $11701170/7200 =.163 (.153)
3 $15001500/10800=.139
$12551255/10800 =.116 (.111)
20 $1000010000/72000=.139
$27002700/72000 =.038
*Note: 1000 + .85*1*100 = 1085 (maybe should be 1000 in a family of 1!
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Life in the Cell – Working with
Family Fixturing Ideas• Earlier we found the text author stating that the cost
of inventory in a batch is independent of schedule – here we see this may not be the case!
• In a cell, setting up the family fixture is timeconsuming – but changing between family members isquick and easy – only the time to remove an adaptorand addition of a new one (or not!)
• This leads to the second rung of the factory with afuture – SMED – if scheduling is rational in the cells!
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Topics
What is Cell Manufacturing System?
CMS and Group Technology
Clustering Techniques: the Fundamental Issue in Cell Development
Clustering Methods: Computing Similarity Coefficients
Clustering Methods: Rank order Clustering
Alternative means to Develop Cells/Families
Life in the Cell – Working with Family Fixturing Ideas
Conclusion
8/11/2019 Cell Manufacturing System
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Lean Manufacturing is then
INTIMATELY tied to CMS and GT• These methods add
efficiency to the productionfloor
• They improve our qualitypicture
• They empower employees
• They reduce setup andproduct change time
• They mean moreproductivity
• The JUST WORK!
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8/11/2019 Cell Manufacturing System
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VIDEO
8/11/2019 Cell Manufacturing System
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APPENDIX
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CMS and its relationship to Job and
Flow Shops:• We can define the movement in a Job Shop(mathematically) this way for any product i:
• Pr(1→2)i = Pr(1→3)i = Pr(1→4)i = …= Pr(1→n)I
• While in a Flow Shop:• Pr(1→2)i = 1 and Pr(1→n)i = 0 (n 2)
• In developing CMS manufacturing systems weare trying to make all part flows act like Flowshop mathematics!