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Cellular Manufacturing
Sections:
1. Part Families2. Parts Classification and Coding
3. Production Flow Analysis
4. Cellular Manufacturing
5. Applications in Group Technology
6. Quantitative Analysis in CellularManufacturing
Recap
GT
Define Relation with lay out
Types
Visual
Coding
PFA
Cellular Manufacturing Systems
Cellular Manufacturing
Application of group technology in which dissimilarmachines or processes are aggregated into cells,each of which is dedicated to the production of apart family or limited group of families
Typical objectives of cellular manufacturing: To shorten manufacturing lead times
To reduce WIP
To improve quality
To simplify production scheduling
To reduce setup times
Composite Part Concept
A composite partfor a given family is a hypothetical partthat includes all of the design and manufacturingattributes of the family
In general, an individual part in the family will havesome of the features of the family, but not all of them
A production cell for the part family would consist ofthose machines required to make the composite part
Such a cell would be able to produce any familymember, by omitting operations corresponding tofeatures not possessed by that part
Composite Part ConceptComposite part concept:
(a) the composite part for a family of machined rotational
parts, and
(b) the individual features of the composite part
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Part Features and Corresponding
Manufacturing Operations
Design feature Corresponding operation
1. External cylinder Turning2. Face of cylinder Facing
3. Cylindrical step Turning
4. Smooth surface External cylindricalgrinding
5. Axial hole Drilling
6. Counter bore Counterboring
7. Internal threads Tapping
Machine Cell Designs
1. Single machine
-One machine plus supporting fixtures & tooling1. Multiple machines with manual handling
Often organized into U-shaped layout
2. Multiple machines with semi-integrated handling
3. Automated cell automated processing andintegrated handling
Flexible manufacturing cell
Flexible manufacturing system
Machine Cell with Manual Handling
U-shaped machine cell with manual part handlingbetween machines
Cell with Semi-Integrated Handling
In-line layout using mechanized work handlingbetween machines
Cell with Semi-Integrated Handling
Loop layout allows variations in part routingbetween machines
Cell with Semi-Integrated Handling
Rectangular layout also allows variations in part routingand allows for return of work carriers if they are used
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Four Types of Part Moves in
Mixed Model Production System Key Machine Concept
Applies in cells when there is one machine (the
key machine) that is more expensive orperforms certain critical operations
Other machines in the cell are supporting machines
Important to maintain high utilization of keymachine, even if this means lower utilization of
supporting machines
Applications of Group Technology
In product manufacturing
In product Design
Manufacturing Applications
of Group Technology Different ways of forming machine cells:
Informal scheduling and routing of similar partsthrough selected machines to minimize setups
Virtual machine cells dedication of certainmachines in the factory to produce part families,but no physical relocation of machines
Formal machine cells machines are physicallyrelocated to form the cells
Automated process planning Modular fixtures Parametric programming in NC
Benefits of Group Technology
in Manufacturing
Standardization of tooling, fixtures, and setups isencouraged
Material handling is reduced Parts are moved within a machine cell rather than the entire
factory Process planning and production scheduling are
simplified
Work-in-process and manufacturing lead time arereduced
Improved worker satisfaction in a GT cell Higher quality work
Product Design Applications
of Group Technology
Design retrieval systems Industry survey: For new part designs,
Existing part design could be used - 20%
Existing part design with modifications 40% New part design required 40%
Simplification and standardization of designparameters such as tolerances, chamfers,hole sizes, thread sizes, etc.
Reduces tooling and fastener requirements inmanufacturing
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QuantitativeAnalysisinCellularManufacturing
Grouping parts and machines by RankOrder Clustering
Arranging machines in a GT Cell
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(12)i = Pr(13)i = Pr(14)i = = Pr(1n)I
While in a Flow Shop:
Pr(12)i = 1 and Pr(1n)i = 0(n 2)
In developing CMS manufacturing systems weare trying to make all part flows act like Flow
shop mathematics!
Examining a Cell in the CMS:
NoticeMWormulti-functionalworkersthisteamisresponsibleforallproductionwithintheircell
CMS and Group Technology (GT) CMS layout are based on recognizing similarities in
products similarities in geometry, size, materialsand processing requirements
This similar products are collected Groupedinstead of being treated as individuals
Leads to product families that visit similarequipment and populate their cells productionschedule
Simpler setups like in a Job shop can follow and theworkers become multifunctional and responsiblefor all aspects of a product and its quality
Cells can be scheduled to produce synchronouslybringing the various sub-assemblies in as needed at
final assembly with greater variety built in
CMS and Group Technology (GT)CMS and Group Technology (GT)
NOTE:Step1isCMSafundamentalactioninLEANMFGing
BuildingtheFACTORYWithAFUTURE
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CMS and Group Technology (GT) Benefits of GT and CMS (Companies Reporting):
52%Report reduction in new part design
10%Report reduction in #of new drawings thru
standardization 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:ReportedbycompaniesinasurveyofadoptersofGT
Benefits of GT and CMS (Companies Reporting):
70%Report reduced throughput time (even morereport 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(productivity improvement)
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 and equipment(Family Fixtures)
Part Families follow the same (or similar) processrouting
These are the ideas and activities that offerreported benefits
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 part
family Cells allow development of Multi-functional workers
Cells hold work teams responsible for production andquality They Empowerthe workers
Empowered to set internal schedules
Empowered to assign tasks
Empowered to train and rotate jobs
Etc, etc, etc
Building the CMS Facility
BeforeClustering
AfterClustering
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Recap
GT Define Relation with lay out Types
Visual
Coding
PFA QuantitativeAnalysisinCellularManufacturing
Clustering Method Process Similarity methods Rank Order Method
Arranging Machines in GT Cell
Clustering Methods
Using Process Similarity methods:
Create Machine Part Matrices
Compute machine pair wise Similarity Coefficientcomparisons:
:
is # of parts (in matrix) visiting
both machines of the pair
is # of parts visiting one but not both m achines
ij
jjx
ij
ij
ij jj
here
x
xS
x x
PartNumber
MachineID
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: Computing Similarity Coefficients:
Total Number is: [(N-1)N]/2 = [(5-1)5]/2 = 10 Where N-is No. of machines.
For 25 machines (typical number in a small Job Shop): 300Sijs
Here they are:
1.33
1 2
00
0 4
2.67
2 1
AB
AC
AD
S
S
S
Continuing:
00
0 5
00
0 4
2.67
2 1
00
0 5
00
0 5
2.67
2 1
00
0 6
AE
BC
BD
BE
CD
CE
DE
S
S
S
S
S
S
S
Here, if the similaritycoefficient is >0.33 consider
clustering
This criteria meansclustering:
A&D, A&B, B&D
C & E
De-clustering: A&C, A&E, B&C, B&E and C&D,
D&E
Continuing: Examining our Matrix and our freshly
clustered machine cells, we develop 2 partfamilies:
For the Cell A/D/B: Part Numbers 2, 3 & 5
For the Cell C/E: Part Numbers 1, 4 & 6
Care must be taken (in most cases) to assure thateach cell has all the machines it needs sometimes a couple of families need a keymachine
In this case, the manager must decide to either replicatethe common machine or share it between the cells creatinga bottleneck and scheduling problem for each cell
This is typically one of the cost problems in CMS systems
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Summarizing
(Process Similarity Method):
Make Machine/Part Matrix
Compute Similarity Coefficients Cluster Machines with positive (>.33) Sijs
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-Cell basis
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 by
structuring 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
scanning after several ordering iterations
Rank Order Clustering Method:
Steps:1. For each row of the machine/part matrix (M/P/M) read the pattern of cell
entries as a binary word. Rank the rows by decreasing binary value.Equal values stay in same order.
2. Ask if newly ranked rows in the matrix are the same as previous order? Yes (STOP) No (continue)
3. Re-form the M/P/M with rows in new descending order. Now rank thecolumns by decreasing binary word weight. Columns of equal weight areleft where they are
4. Are current column weights the same as current column order? Yes(STOP), No (continue)
5. Re-form the matrix column order per rank order (highest to left) andreturn to#1.
Lets try it with our earlier problem:
PartNumber
MachineID
X 1 2 3 4 5 6
A 1 1
B 1 1
C 1 1
D 1 1 1
E 1 1 1
Step 1:
PartNumbers D.Equiv Rank
MachineID
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
Step2:MustReorder!
Step 3:
PartNumber
B.WT. 1 2 3 4 5 6
MachineID
E 24 1 1 1
C 23 1 1
D 22 1 1 1
B 21 1 1
A 20 1 1
D.Equiv24+23
=2422+21=6
22+21+20=7
24+23=24
22+20=5
24=16
Rank 1 5 4 2 6 3
Step4:MustReorder
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Back at Step 1:
PartNumber D.Eqv Rank
1 4 6 3 2 5
BWt: 25 24 23 22 21 20
MachineID
E 1 1 125+24+23=56
1
C 1 125+24=48
2
D 1 1 122+21+20
=73
B 1 1 22+21=6 4
A 1 1 22+20=5 5
Orderstaysthesame:STOP!
GreatClusterResult! Issues in Clustering:
R/O clustering oscillations indicating need of machinereplication (happens often!)
Presence of Outliers and/or Voids in the finishedclusters
Outliers indicate the need of machine replication
Voids indicate skippedmachines in a cell
Generally speaking, these clustering algorithms aredesigned to convert existing routes for facility re-organization
They require a previous engineering study to be performed todevelop a series of routers on a core sample of parts thatrepresent most of the production in the shop
Alternative means to Develop Cells/Families:
Most often companies rely on Classificationand Coding (C&C) systems for analyzing theirpart mix
These codes can be general purpose orcompany specific General Purpose:
Opitz is a german developed code for machined parts(see over)
KC1, KC2 and KK1 systems Japanese government labbased codes for machined parts
Brish a british developed code for general material use
Foundry codes have been developed by several groups(see Lindeke & Rubinovich, 1987 in USA)
Examining Opitz Code:
Examining Opitz Code:
ThisFormcodeistheOpitzCodeSolutiononthisshaft-likepart
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 importantcharacteristics of the part/process mix, physical
characteristics like size, geometric features, or
material, etc.
Since they are specific they tend to be more accuratein building part families
Alternative means to Develop Cells/Families:
Using GT Classification and codingsystems, parts are coded by experts at
the company
The newly coded part is used to searchexisting production databases forsimilarly coded products
The new part is assigned to the family itmost closely matches
Its routing is thus set and only minorvariation needs to be considered
Using specific digits, a company cantarget marketing in certain areas of theirproduct mix
Alternative means to Develop Cells/Families:
In a greenfield shop, managers candevelop facility designs (in the formof reasonable cells) by selectingreasonable seed parts as suggestedby their GT C&C system
These seeds can be used to buildrouters and, hence appropriatemachine clusters
Using GT C&C systems, processclusters evolve from parts as opposedto clustering evolving by process
Fixturing
Fixturingis a means to speed up partloading and increase accuracy of machine
and mfg. processes
These are tools that:
Locate the work for geometric control ofvarious DOF
May also provide a means to guide thetooling used to perform the operations (Jigs)
Before being used these tool must beaccurately placed on the machine often a
time consuming task since their placement
tolerance must be 10x better than part
tolerance!
Fixturing
In CMS, it is often possible to build Family Fixtures
These are fixtures that can be shared among all theparts in the family (because they are similar
geometrically and by mfg. process) thus reducingtime to set-up any part in the family
The Family Fixture is generic and may (likely) requirethe addition of specific change pieces for different
members of the family but definitely not different
fixtures.
Fixturing
Example of Cost Savings:Shop cost is Rs. 50/hour
Hand setup is 2 minutes/piece (lot is 400parts)
Setup on Fixture is 0.03 min/partSaving of 1.97 min = .033 hr = Rs.1.64/part
If machine takes 5 minutes/part, Production rate increasesfrom8.57 parts/hour to 11.93 parts/hr almost a 40%increase!
The company would invest in Fixturing tools if the cost of afixture applied to a given part over the life of the tooling
and part production is less than the Rs.1.64 savings from
reduced setup times
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Fixturing
Conventional fixturing means a separate
fixture for each part made Family fixturing means a separate fixture for
each family made (but several adaptors for
individuals in the family)
Typically, Family Fixtures cost more thanconventional fixtures so lets do a cost
analysis
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
CP n
P =numberofpartsneedingtooling
Cdisdesigncost;Cmismaterialcost; Cfisfabricationcost;Ciisinventorycost; Chishandlingcost
n=lifetimenumberofpartstobemade(est.)
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
toolu
C C C i
C
C C C C C C
CC
Q n
Q =numberofpartsinFamily
Cdisdesigncost;Cmismaterialcost; Cfisfabricationcost;Ciisinventorycost; Chishandlingcost
n=lifetimenumberofeachpartinfamilytobemade(est.)
Example:
Conventional GTIdeas
MainTool Rs.500 Rs.1000
#F.Required 1/part 1forfamily
CostAdaptor NA Rs.100
No.AdaptorsReqr NA .85/part
TypicalOrderSize 400 400
TypicalBatch/lifetime 3batch/yr/3yrs=3600 3batch/yr/3yrs=3600
Family Fixturing:
No.Parts C.Tools UnitCost GTTools UnitCost
1 Rs.500 500/3600 =.139 Rs.1085*1085/3600=.301
(.278)
2 Rs.1000 1000/7200=.139 Rs.1170 1170/7200=.163(.153)
3 Rs.1500 1500/10800=.139 Rs.12551255/10800=.116
(.111)
20 Rs.1000010000/72000=.1
39Rs.2700
2700/72000 =
.038
*Note:1000+.85*1*100=1085(maybeshouldbe1000inafamilyof1!
Family Fixturing:
Earlier we found the text author stating that the costof 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
is quick and easy only the time to remove an
adaptor and 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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Lean Manufacturing is then INTIMATELY tied to
CMS and GT
These methods add efficiencyto the production floor
They improve our qualitypicture
They empower employees
They reduce setup andproduct change time
They mean more productivity
They JUST WORK!
Recap
GT Define
Relation with lay out Types Visual Coding PFA
QuantitativeAnalysisinCellularManufacturing
Clustering Method Process Similarity methods
Rank Order Method
Arranging Machines in GT Cell Family Fixtureing
FMS
CAPP
Flexible Manufacturing Systems
Flexible Manufacturing Systems
Sections:
1. What is a Flexible Manufacturing System?
2. FMS Components
3. FMS Applications and Benefits
4. FMS Planning and Implementation Issues
5. Quantitative Analysis of Flexible Manufacturing
Systems
Where to Apply FMS Technology
The plant presently either: Produces parts in batches or
Uses manned GT cells and management wants toautomate the cells
It must be possible to group a portion of theparts made in the plant into part families
The part similarities allow them to be processedon the FMS workstations
Parts and products are in the mid-volume,mid-variety production range
Flexible Manufacturing System - Defined
A highly automated GT machine cell, consisting of agroup of processing stations (usually CNC machinetools), interconnected by an automated materialhandling and storage system, and controlled by anintegrated computer system
The FMS relies on the principles of GT No manufacturing system can produce an unlimited
range of products
An FMS is capable of producing a single part family or alimited range of part families
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Flexibility Tests in an Automated
Manufacturing System
To qualify as being flexible, a manufacturing systemshould satisfy the following criteria (yesanswerfor each question):
1. Can it process different part styles in a non-batchmode?
2. Can it accept changes in production schedule?
3. Can it respond gracefully to equipment malfunctionsand breakdowns?
4. Can it accommodate introduction of new partdesigns? Automated manufacturing cell with two
machine tools and robot. Is it a flexible cell?
AutomatedManufacturingCell
Is the Robotic Work Cell Flexible?
1. Part variety test
Can it machine different part configurations ina mix rather than in batches?
2. Schedule change test
Can production schedule and part mix bechanged?
Is the Robotic Work Cell Flexible?
3. Error recovery test
Can it operate if one machine breaks down?
Example: while repairs are being made on the brokenmachine, can its work be temporarily reassigned to the
other machine?
4. New part test
As new part designs are developed, can NC partprograms be written off-line and then downloaded
to the system for execution?
Types of FMS
Kinds of operations
Processing vs. assembly
Type of processing
If machining, rotational vs. non-rotational
Number of machines (workstations):
1. Single machine cell (n = 1)
2. Flexible manufacturing cell (n = 2 or 3)
3. Flexible manufacturing system (n = 4 or more)
Single-Machine Manufacturing Cell
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A single-machine CNC machining cell
(photo courtesy of Cincinnati Milacron) Flexible Manufacturing Cell
A two-machine flexible manufacturing cell for machining
(photo courtesy of Cincinnati Milacron)
A five-machine flexible manufacturing system for machining
(photo courtesy of Cincinnati Milacron)
Features of the Three CategoriesFMS Types
Level of Flexibility
1. Dedicated FMS
Designed to produce a limited variety of part styles
The complete universe of parts to be made on thesystem is known in advance
Part family likely based on product commonalityrather than geometric similarity
2. Random-order FMS
Appropriate for large part families
New part designs will be introduced
Production schedule is subject to daily changes
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Dedicated vs. Random-Order FMSs FMS Components
1. Workstations
2. Material handling and storage system
3. Computer control system
4. Human labor
Workstations
Load and unload station(s) Factory interface with FMS
Manual or automated
Includes communication interface with worker tospecify parts to load, fixtures needed, etc.
CNC machine tools in a machining type system CNC machining centers
Milling machine modules
Turning modules
Assembly machines
Material Handling and Storage
Functions: Random, independent movement of parts
between stations
Capability to handle a variety of part styles Standard pallet fixture base
Workholding fixture can be adapted
Temporary storage
Convenient access for loading and unloading
Compatibility with computer control
Material Handling Equipment
Primary handling system establishes basic FMSlayout
Secondary handling system - functions:
Transfers work from primary handling system toworkstations
Position and locate part with sufficient accuracy andrepeatability for the operation
Reorient part to present correct surface forprocessing
Buffer storage to maximize machine utilization
Five Types of FMS Layouts
The layout of the FMS is established by thematerial handling system
Five basic types of FMS layouts
1. In-line
2. Loop
3. Ladder
4. Open field
5. Robot-centered cell
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FMS In-Line Layout
Straight line flow, well-defined processingsequence similar for all work units
Work flow is from left to right through the sameworkstations
No secondary handling system
FMS In-Line Layout
Linear transfer system with secondary partshandling system at each workstation to facilitateflow in two directions
FMS Loop Layout
One direction flow, but variations in processingsequence possible for different part types
Secondary handling system at each workstation
FMS Rectangular Layout
Rectangular layout allows recirculation of palletsback to the first station in the sequence afterunloading at the final station
FMS Ladder
Layout
Loop with rungs toallow greater variation
in processing sequence
FMS Open
Field Layout
Multiple loopsand ladders,
suitable forlarge part
families
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Robot-Centered Cell
Suited to the
handling ofrotational parts and
turning operations
FMS Computer Functions
1. Workstation control
Individual stations require controls, usuallycomputerized
2. Distribution of control instructions toworkstations
Central intelligence required to coordinateprocessing at individual stations
3. Production control
Product mix, machine scheduling, and otherplanning functions
FMS Computer Functions
4. Traffic control
Management of the primary handling system tomove parts between workstations
5. Shuttle control
Coordination of secondary handling system withprimary handling system
6. Workpiece monitoring
Monitoring the status of each part in the system
FMS Computer Functions
7. Tool control
Tool location Keeping track of each tool in the system
Tool life monitoring Monitoring usage of each cutting tool and determining when
to replace worn tools
8. Performance monitoring and reporting
Availability, utilization, production piece counts, etc.
9. Diagnostics
Diagnose malfunction causes and recommend repairs
Duties Performed by Human Labor
Loading and unloading parts from the system
Changing and setting cutting tools
Maintenance and repair of equipment NC part programming
Programming and operating the computersystem
Overall management of the system
FMS Applications
Machining most common application ofFMS technology
Assembly
Inspection
Sheet metal processing (punching, shearing,bending, and forming)
Forging
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FMS at Chance-Vought Aircraft(courtesy of Cincinnati Milacron) FMS for Sheet Metal Fabrication
FMS Benefits
Increased machine utilization Reasons:
24 hour operation likely to justify investment
Automatic tool changing
Automatic pallet changing at stations
Queues of parts at stations to maximize utilization
Dynamic scheduling of production to account for changesin demand
Fewer machines required
Reduction in factory floor space required
FMS Benefits
Greater responsiveness to change
Reduced inventory requirements Different parts produced continuously rather than in
batches
Lower manufacturing lead times
Reduced labor requirements
Higher productivity
Opportunity for unattended production Machines run overnight ("lights out operation")
FMS Planning and Design Issues
Part family considerations Defining the part family of families to be processed
Based on part similarity
Based on product commonality Processing requirements
Determine types of processing equipment required
Physical characteristics of workparts Size and weight determine size of processing
equipment and material handling equipment
FMS Planning and Design Issues
Production volume Annual quantities determined number of machines
required
Types of workstations Variations in process routings
Work-in-process and storage capacity
Tooling
Pallet fixtures
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FMS Operational Issues
Scheduling and dispatching
Launching parts into the system at appropriatetimes
Machine loading
Deciding what operations and associatedtooling at each workstation
Part routing
Selecting routes to be followed by each part
FMS Operational Issues
Part grouping
Which parts should be on the system at one time Tool management
When to change tools
Pallet and fixture allocation
Limits on fixture types may limit part types that canbe processed
Quantitative Analysis of
Flexible Manufacturing Systems
FMS analysis techniques:1. Deterministic models
2. Queueing models
3. Discrete event simulation
4. Other approaches, including heuristics
Deterministic models1. Bottleneck model - estimates of production rate,
utilization, and other measures for a given product mix
2. Extended bottleneck model - adds work-in-processfeature to basic model
Parameters
Design Description (p.702)
Assumption:StationscannotwaitfortheMHD
Design Principle
Algorithm used for
calculating thethroughput(X) of the
material-handling
device (MHD) based on
Mean Value Analysis.
(p.703)
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Design Principle Cont.QueueingNetworkModel
Pallets come out from a blackbox and wait for service in aqueue where the MHD serves each pallet in FIFO fashion.
Request for service are made by the pallets which are in theblackbox.
Assumption: rate at which pallet arrives from the blackbox is afunction of (N-m):
N=num.of pallets / m=pallets waiting in the queue for MHD M/M/C/N queueing model. Reference [29]
Using this model, the service rat e() for the pallet can befound, and hence the average waiting time in the queue orMHD.
Design Principle Cont. Algorithm to calculate theaveragewaiting time(Wr) of MHD.
Results
Adaptive Neuro-Fuzzy System (ANFS) network
- Fuzzy toolbox in MATLAB used for approximating Tr, X and Wr.
- The performance measures are found by varying different
system parameters: C, , N and S.
- Using these parameters as inputs, an ANFS network was built.
- ANFS measure values serve as a comparison for the analyticalvalues calculated using MVA.
- Fix set of Homogeneous and Heterogeneous processing timesfor fuzzy and MVA measurements:
Results Cont.
Parameters:
N=24,S=15, Q=5
As the number of MHD
(C) increases, the
throughput (X) and
average time (Wr)
decreases.
Results Cont.
Parameters:
N=24, =15, Q=5- Effect of S on X and Wr for
C=1 and C=5
- X and Wr increase withincreasing S.
- However, for heterogeneous
processing time these take
lower values in comparison
to the homogeneous one.
- Both X and Wr are larger for
C=1 compared to C=5
Results Cont.
Parameters:
S=15, =0.25, Q=5
- As N increases, both X andWr decrease
- For homogeneous values of
processing time these take
the higher value in
comparison to the
heterogeneous one
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Results Cont.
- Result of mean servicetime (Tr) and (Wr) by
varying the move timemultiplier ().
- As increases, Trincreases linearly
- The waiting time (Wr)increases exponentiallyas also increases.
What the Equations Tell Us
For a given part mix, the total production rate is
ultimately limited by the bottleneck station If part mix ratios can be relaxed, it may be possible
to increase total FMS production rate by increasing
the utilization of non-bottleneck stations
As a first approximation, bottleneck model can beused to estimate the number of servers of each
type to achieve a specified overall production rate
What the Equations Tell Us
The number of parts in the FMS at any one timeshould be greater than the number of servers
(processing machines) in the system
Ratio of two parts per server is probably optimum
Parts must be distributed throughout the FMS,especially in front of the bottleneck station
If WIP is too low, production rate is impaired
IF WIP is too high, MLT increases
CAPP
Computer Aided Process Planning
(CAPP)
CAPP is the use of computer based decisionsupport systems in process planning.
CAPP offers potential benefit in terms of reducing the routine clerical work of
manufacturing engineers and helps in
producing rational, consistent and optimal
process plans
PROCESSPLANNING
Process Planning i s that Function Within a Manufacturing
Facili ty that Establishes whi ch Machining Processes &Parameters are to be Used (As Well As Those Machin es Capable
Of Performi ng These Processes) To Conv ert (Machine) A PiecePart From Its Init ial Form To A Final Form Predetermi ned(Usually By A Design Engineer) From An Engineering Drawing.
(i.e. The Preparation of the Detail ed Work Inst ructi ons to Produc e aPart)
Bridge
Design Manufacturing
Processplanningbridgesdesignandmanufacturing
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Computer Aided Process Planning (CAPP) Computer Aided Process Planning (CAPP)
VARIANTPROCESSPLANNING
USESTHESIMILARITYAMONGCOMPONENTSTORETRIEVEEXISTINGPROCESSPLANS(WHICHCANBEMODIFIED)
OVERVIEW:TWOSTAGESFORVPSYSTEMS
1.PREPARATORYSTAGE
EXISTINGPARTSCODED&CLASSIFIED(I.E.GTISAPREREQUISITE)PARTFAMILIESORGANIZEDSTANDARDPLANSDEVELOPEDDATABASESCREATED
(NOTE:THISSTAGEISLABORINTENSIVE)Contd
PartDrawing
Coding
FamilyFormation
ProcessPlan
FamilyOne
StandardPlanFile
(IndexedbyFamily
Matrix)
1.PREPARATORYSTAGEOFVARIANTPROCESSPLANNING
2. PRODUCTONSTAGEOFVARIANTROCESSPLANNING
Coding FamilySearchStandardPlan
File
Editing StandardPlanRetrieval
ProcessPlan
Computer aided process control
Pressure
temperature
flow
level
proximity
force
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Computer aided process control