Group Technology Group Technology and Cellular and Cellular
ManufacturingManufacturing
Eng. Ahmed Al AfeefyEng. Ahmed Al Afeefy
What is Group Technology What is Group Technology (GT)(GT)??
GT is a theory of management based on GT is a theory of management based on the principle that similar things should be the principle that similar things should be done similarlydone similarly
GT is the realization that many problems GT is the realization that many problems are similar, and that by grouping similar are similar, and that by grouping similar problems, a single solution can be found to problems, a single solution can be found to a set of problems thus saving time and a set of problems thus saving time and efforteffort
GT is a manufacturing philosophy in which GT is a manufacturing philosophy in which similar parts are identified and grouped similar parts are identified and grouped together to take advantage of their together to take advantage of their similarities in design and productionsimilarities in design and production
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Implementing GTImplementing GT
Where to implement GT?Where to implement GT? „„Plants using traditional batch Plants using traditional batch
production and „process type layoutproduction and „process type layout „ „ If the parts can be grouped into part If the parts can be grouped into part
familiesfamilies
„„How to implement GT?How to implement GT? „„Identify part familiesIdentify part families „„Rearrange production machines into Rearrange production machines into
machine cellsmachine cells
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Types of LayoutTypes of LayoutIn most of today’s factories it is possible to divide all the made components into families and all the machines into groups, in such a way that all the parts in each family can be completely processed in one group only.
The three main types of layout are:
• Line (product) Layout
• Functional Layout
• Group Layout44
LineLine (product) (product) Layout Layout•It involves the arrangements of machines in one line, depending on the sequence of operations. In product layout, if there is a more than one line of production, there are as many lines of machines.
•Line Layout is used at present in simple process industries, in continuous assembly, and for mass production of components required in very large quantities.
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Functional LayoutFunctional Layout•In Functional Layout, all machines of the same type are laid out together in the same section under the same foreman. Each foreman and his team of workers specialize in one process and work independently. This type of layout is based on process specialization.
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Group LayoutGroup Layout
•In Group Layout, each foreman and his team specialize in the production of one list of parts and co-operate in the completion of common task. This type of layouts based on component specialization.
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The Difference between group and functional The Difference between group and functional layoutlayout::
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Large manufacturing system can Large manufacturing system can be decomposed into smaller be decomposed into smaller subsystems of part families based subsystems of part families based on similarities inon similarities in
1. 1. design attributesdesign attributes and and 2. 2. manufacturing manufacturing
featuresfeatures99
Identifying Part Identifying Part FamiliesFamilies
Design Attributes:Design Attributes: part configuration part configuration (round or (round or
prismatic)prismatic) dimensional envelope dimensional envelope (length to (length to
diameter ratio)diameter ratio) surface integrity surface integrity (surface roughness, (surface roughness,
dimensional tolerances) dimensional tolerances) material typematerial type raw material state raw material state (casting, forging, (casting, forging,
bar stock, etc.)bar stock, etc.) 1010
Identifying Part Identifying Part FamiliesFamilies
Part Manufacturing Features:Part Manufacturing Features: operations and operation sequences operations and operation sequences
(turning, milling, etc.)(turning, milling, etc.) batch sizesbatch sizes machine toolsmachine tools cutting toolscutting tools work holding deviceswork holding devices processing timesprocessing times
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Identifying Part Identifying Part FamiliesFamilies
Group technologyGroup technology emphasis emphasis on part families based on on part families based on similarities in design similarities in design attributes and manufacturing, attributes and manufacturing, therefore therefore GTGT contributes to contributes to the integration of CAD and the integration of CAD and CAM. CAM.
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Identifying Part Identifying Part FamiliesFamilies
Part FamiliesPart FamiliesA part family is a collection having similar:
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Three methods for identifying parts families
• Visual inspection
• Classification and coding
• Production flow analysis
Forming Part Families –Forming Part Families –1. Visual Inspection Method1. Visual Inspection Method
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incorrect resultsincorrect resultshuman errorhuman errordifferent judgment by different different judgment by different
peoplepeopleinexpensive inexpensive least sophisticatedleast sophisticatedgood for small companies having good for small companies having
smaller number of partssmaller number of parts1515
Forming Part Families –Forming Part Families –1. Visual Inspection Method1. Visual Inspection Method
Forming Part Families –Forming Part Families –2. Classification and Coding2. Classification and Coding
Coding:Coding: The process of assigning symbols to The process of assigning symbols to
the parts. Where the symbols the parts. Where the symbols represent design attributes of parts, represent design attributes of parts, manufacturing features of parts, or manufacturing features of parts, or both both
Classification:Classification: „„The process of categorization of a set The process of categorization of a set
of parts into part familiesof parts into part families1616
A GT code is a string of characters A GT code is a string of characters capturing information about an item capturing information about an item
Three main types of coding systems Three main types of coding systems structure: structure:
„„Mono-code or hierarchical structure Mono-code or hierarchical structure „„Poly-code, or chain-type structurePoly-code, or chain-type structure „„Mixed-mode structureMixed-mode structure
Forming Part Families –Forming Part Families –Classification and CodingClassification and Coding
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Mono-codeMono-code
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A monocodeA monocode (hierarchical code) (hierarchical code) provides a large amount of provides a large amount of information in a relatively small information in a relatively small number of digitsnumber of digits
Useful for storage and retrieval of Useful for storage and retrieval of design-related information such as design-related information such as part geometry, material, sizepart geometry, material, size, , etc.etc.
it is difficult to capture information it is difficult to capture information on manufacturing sequences in on manufacturing sequences in hierarchical manner, so applicability hierarchical manner, so applicability of this code in manufacturing is of this code in manufacturing is rather limited rather limited
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Mono-codeMono-code
Poly-codePoly-code
The code symbols are independent of each The code symbols are independent of each otherother
Each digit in specific location of the code Each digit in specific location of the code describes a unique property of the work describes a unique property of the work piecepiece– it is easy to learn and useful in it is easy to learn and useful in
manufacturing situations where the manufacturing situations where the manufacturing process have to be manufacturing process have to be describeddescribed
– the length of a poly-code may become the length of a poly-code may become excessive because of its unlimited excessive because of its unlimited combinational featurescombinational features
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PolycodePolycode
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PolycodePolycode
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[[Mixed-modeMixed-mode ] ]The OPITZ The OPITZ classification systemclassification system::
it is a it is a mixedmixed (hybrid) coding system (hybrid) coding system developed by developed by OPTIZOPTIZ, Technical , Technical
University of Aachen, 1970University of Aachen, 1970 it is widely used in industryit is widely used in industry it provides a basic framework for it provides a basic framework for
understanding the classification and understanding the classification and coding processcoding process
it can be applied to machined parts, it can be applied to machined parts, non-machined parts (both formed and non-machined parts (both formed and cast) and purchased partscast) and purchased parts
it considers both it considers both designdesign and and manufacturingmanufacturing information information 2323
Mixed-modeMixed-mode
Form code:
„ Focus on part geometry dimensions and features relevant to part design
Supplementary code
„ Includes information relevant to manufacturing, such as raw material, tolerance, and surface roughness
Secondary code
„ Intended to identify the production operation type and sequence.
„ It can be designed by the user firm to serve its own needs 2424
Basic Structure of the OPTIZBasic Structure of the OPTIZ
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Basic Structure of the OPTIZ Basic Structure of the OPTIZ SystemSystem
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Form Code (digits 1 – 5)Form Code (digits 1 – 5)
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Example: Optiz part coding System• Given the rotational part design below, determine the form
code in the Optiz parts classification and coding system.
Solution• Length-to-diameter ratio: L/D = 1.5 Digit 1
= 1
• External shape: both ends stepped with screw thread on one endDigit 2 = 5
• Internal shape: part contains a through hole Digit 3 = 1
• Plane surface machining: none Digit 4 = 0
• Auxiliary holes, gear teeth, etc.: none Digit 5 = 0
The form code in the Optiz system is 15100
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ExampleExample
Part class:Part class:Rotational part, L/D = 9.9/4.8 ≈ 2.0 based on the pitch �Rotational part, L/D = 9.9/4.8 ≈ 2.0 based on the pitch �
circle diameter of the gear, so the first digit = 1circle diameter of the gear, so the first digit = 1 ��External shape:External shape:The part is stepped on one side with a functional groove, The part is stepped on one side with a functional groove,
so the second digit is 3so the second digit is 3 Internal shape:Internal shape: The third digit is 1 because of the through holeThe third digit is 1 because of the through hole ��Plain surface machining:Plain surface machining: The fourth digit is 0 because there is no plain surface �The fourth digit is 0 because there is no plain surface �
machiningmachining ��Auxiliary holes and gear teeth:Auxiliary holes and gear teeth: The fifth digit is 6 because there are spur gear teeth �The fifth digit is 6 because there are spur gear teeth �
on the parton the part 2929
Forming Part Families –Forming Part Families –Classification and Coding: Classification and Coding:
Production 3. Flow Analysis (PFA)Production 3. Flow Analysis (PFA) PFA is a method for identifying part families PFA is a method for identifying part families
and associated machine groupings based and associated machine groupings based on the required manufacturing processes on the required manufacturing processes need for each partneed for each part
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Selection of Classification and Selection of Classification and Coding SystemsCoding Systems
Define your objectives, reasons and usersDefine your objectives, reasons and users Try to get consensus so that the classification and coding �Try to get consensus so that the classification and coding �
system is useful in design purchasing manufacturing quality etc.system is useful in design purchasing manufacturing quality etc.
Robustness and ExpandabilityRobustness and Expandability Can it work with the current product and accommodate Can it work with the current product and accommodate
unknown future products and applications.unknown future products and applications.
Automation and EfficiencyAutomation and Efficiency Is it easy to get information in and out in a timely manner, and is Is it easy to get information in and out in a timely manner, and is
the coding system able to handle present and future products.the coding system able to handle present and future products.
Simplicity and User InterfaceSimplicity and User Interface Will people use it?Will people use it?
CostCost As an engineering decision with far reaching impact, what’s the �As an engineering decision with far reaching impact, what’s the �
true cost?true cost?
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BENEFITS OF GROUP BENEFITS OF GROUP TECHNOLOGYTECHNOLOGY
It affects all areas of a company, including:It affects all areas of a company, including:
engineeringengineering equipment specification equipment specification facilities planning facilities planning process planningprocess planning production control production control quality control quality control tool design tool design purchasing purchasing serviceservice
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BENEFITS OF GROUP BENEFITS OF GROUP TECHNOLOGYTECHNOLOGY
Some of the well-known tangible and Some of the well-known tangible and intangible benefits of implementing GT :intangible benefits of implementing GT :
1.1.Engineering designEngineering design
• Reduction in new parts designReduction in new parts design
• Reduction in the number of drawings Reduction in the number of drawings through standardizationthrough standardization
• Reduction of number of similar parts, easy Reduction of number of similar parts, easy retrieval of similar functional parts, and retrieval of similar functional parts, and identification of substitute partsidentification of substitute parts
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BENEFITS OF GROUP BENEFITS OF GROUP TECHNOLOGYTECHNOLOGY
2. Layout planning2. Layout planning
Reduction in production floor space Reduction in production floor space requiredrequired
Reduced material-handling effortReduced material-handling effort
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BENEFITS OF GROUP BENEFITS OF GROUP TECHNOLOGYTECHNOLOGY
3. Specification of equipment, tools, 3. Specification of equipment, tools, jigs, and fixturesjigs, and fixtures
Standardization of equipmentStandardization of equipment Implementation of cellular Implementation of cellular
manufacturing systemsmanufacturing systems Significant reduction in up-front costs Significant reduction in up-front costs
incurred in the release of new parts incurred in the release of new parts for manufacturefor manufacture
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BENEFITS OF GROUP BENEFITS OF GROUP TECHNOLOGYTECHNOLOGY
4. Manufacturing: 4. Manufacturing: process planningprocess planning
Reduction in setup time and Reduction in setup time and production timeproduction time
Alternative routing leading to Alternative routing leading to improved part routingimproved part routing
Reduction in number of machining Reduction in number of machining operations and numerical control operations and numerical control (NC) programming time(NC) programming time
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BENEFITS OF GROUP BENEFITS OF GROUP TECHNOLOGYTECHNOLOGY
5. 5. Manufacturing: production controlManufacturing: production control
Reduced work-in-process inventoryReduced work-in-process inventory Easy identification of bottlenecksEasy identification of bottlenecks Improved material flow and reduced Improved material flow and reduced
warehousing costswarehousing costs Faster response to schedule changesFaster response to schedule changes Improved usage of jigs, fixtures, pallets, Improved usage of jigs, fixtures, pallets,
tools, material handling, and tools, material handling, and manufacturing equipmentmanufacturing equipment
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BENEFITS OF GROUP BENEFITS OF GROUP TECHNOLOGYTECHNOLOGY
6. Manufacturing: quality control6. Manufacturing: quality control
Reduction in number of defects leading to Reduction in number of defects leading to reduced inspection effortreduced inspection effort
Reduced scrap generationReduced scrap generation Better output qualityBetter output quality Increased accountability of operators and Increased accountability of operators and
supervisors responsible for quality supervisors responsible for quality production, making it easier to implement production, making it easier to implement total quality control concepts.total quality control concepts.
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BENEFITS OF GROUP BENEFITS OF GROUP TECHNOLOGYTECHNOLOGY
7.7. PurchasingPurchasing
Coding of purchased part leading to Coding of purchased part leading to standardized rules for purchasingstandardized rules for purchasing
Economies in purchasing possible because Economies in purchasing possible because of accurate knowledge of raw material of accurate knowledge of raw material requirementsrequirements
Reduced number of part and raw materialsReduced number of part and raw materials Simplified vendor evaluation procedures Simplified vendor evaluation procedures
leading to just-in-time purchasingleading to just-in-time purchasing
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BENEFITS OF GROUP BENEFITS OF GROUP TECHNOLOGYTECHNOLOGY
8.8. Customer serviceCustomer service
Accurate and faster cost estimatesAccurate and faster cost estimates Efficient spare parts management, Efficient spare parts management,
leading to better customer serviceleading to better customer service Lower lead timesLower lead times
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Cellular ManufacturingCellular ManufacturingCellular manufacturing �Cellular manufacturing �is an application of group technology in manufacturing in �is an application of group technology in manufacturing in �
which all or a portion of a firm’s manufacturing system which all or a portion of a firm’s manufacturing system has been converted into cellshas been converted into cells
A manufacturing cell �A manufacturing cell �is a cluster of machines or processes located in close �is a cluster of machines or processes located in close �
proximity and dedicated to the manufacturing of a family proximity and dedicated to the manufacturing of a family of partsof parts
��Why cellular manufacturing:Why cellular manufacturing: Reduce setup times: By using part family tooling and � �Reduce setup times: By using part family tooling and � �
sequencingsequencing Reduce flow times:By reducing setup and move times �Reduce flow times:By reducing setup and move times �
and wait time for moves and using smaller batch sizesand wait time for moves and using smaller batch sizes Reduce inventories�Reduce inventories� Reduce lead time�Reduce lead time� 4141
Cell DesignCell Design
Design of cellular manufacturing system Design of cellular manufacturing system is a complex exercise with broad is a complex exercise with broad implications for an organization. implications for an organization.
The The cell design processcell design process involves involves issues related to both issues related to both system system structurestructure (Structural Issues) (Structural Issues) and and system operationsystem operation (Procedures Issues) (Procedures Issues)
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StructuralStructural issues includeissues include:: Selection of part families and Selection of part families and
grouping of parts into familiesgrouping of parts into families Selection of machine and process Selection of machine and process
populations and grouping of these into populations and grouping of these into cellscells
Selection of tools, fixtures, and palletsSelection of tools, fixtures, and pallets Selection of material-handling Selection of material-handling
equipmentequipment Choice of equipment layoutChoice of equipment layout
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Cell DesignCell Design
Procedures Issues include:Procedures Issues include: Detailed design of jobsDetailed design of jobs Organization of supervisory and support Organization of supervisory and support
personnel around the cellular structurepersonnel around the cellular structure Formulation of maintenance and inspection Formulation of maintenance and inspection
policiespolicies Design of procedures Design of procedures for production for production
planningplanning, , scheduling, controlscheduling, control, and , and acquisition of related software and hardwareacquisition of related software and hardware
Modification of cost control and reward Modification of cost control and reward systemssystems
Outline of procedures for interfacing with Outline of procedures for interfacing with the remaining manufacturing system (in the remaining manufacturing system (in terms of work flow and information, whether terms of work flow and information, whether computer controlled or not)computer controlled or not)
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Cell DesignCell Design
Evaluation of Cell Design Evaluation of Cell Design DecisionsDecisions
The evaluation of design decisions can The evaluation of design decisions can be categorized as related to either be categorized as related to either
the system structurethe system structure
or or the system operationthe system operation. .
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Typical considerations related to Typical considerations related to the the system structuresystem structure include: include:
Equipment and tooling investment Equipment and tooling investment (low)(low)
Equipment relocation cost (low)Equipment relocation cost (low) Material-handling costs (low)Material-handling costs (low) Floor space requirements (low)Floor space requirements (low) Extent to which parts are completed in Extent to which parts are completed in
a cell (high)a cell (high) Flexibility (high)Flexibility (high) 4646
Evaluation of Cell Design Evaluation of Cell Design DecisionsDecisions
Evaluations of cell system design are Evaluations of cell system design are incomplete unless they relate to the incomplete unless they relate to the
operation of the systemoperation of the system.. A few typical performance variables A few typical performance variables related to related to system operationsystem operation are: are:
Equipment utilization (high)Equipment utilization (high) Work-in-process inventory (low)Work-in-process inventory (low) Queue lengths at each workstation Queue lengths at each workstation
(short)(short) Job throughput time (short)Job throughput time (short) Job lateness (low)Job lateness (low) 4747
Evaluation of Cell DesignEvaluation of Cell Design
Cell Formation ApproachesCell Formation Approaches
1. Machine - Component Group 1. Machine - Component Group AnalysisAnalysis::
Machine - Component Group AnalysisMachine - Component Group Analysis is based on is based on production flow production flow analysisanalysis
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Production flow analysisProduction flow analysis involves four involves four stages:stages:
Stage 1:Stage 1: Machine classificationMachine classification. .
Machines are classified on the basis Machines are classified on the basis of operations that can be performed of operations that can be performed on them. A machine type number is on them. A machine type number is assigned to machines capable of assigned to machines capable of performing similar operations.performing similar operations.
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Machine - Component Machine - Component Group AnalysisGroup Analysis
Stage 2:Stage 2: Checking parts list and Checking parts list and production route informationproduction route information..
For each part, information on the For each part, information on the operations to be undertaken and the operations to be undertaken and the machines required to perform each of machines required to perform each of these operations is checked thoroughly.these operations is checked thoroughly.
Production flow analysisProduction flow analysis involves four involves four stagesstages::
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Machine - Component Machine - Component Group AnalysisGroup Analysis
Stage 3:Stage 3: Factory flow analysisFactory flow analysis..
This involves a micro-level This involves a micro-level examination of flow of components examination of flow of components through machines. This, in turn, through machines. This, in turn, allows the problem to be allows the problem to be decomposed into a number of decomposed into a number of machine-component groups.machine-component groups.
Production flow analysisProduction flow analysis involves four involves four stagesstages::
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Machine - Component Machine - Component Group AnalysisGroup Analysis
Stage 4:Stage 4: Machine-component Machine-component group group analysisanalysis..
An intuitive manual method is An intuitive manual method is suggested to manipulate the matrix to suggested to manipulate the matrix to form cells. However, as the problem form cells. However, as the problem size becomes large, the manual size becomes large, the manual approach does not work. Therefore, approach does not work. Therefore, there is a need to develop analytical there is a need to develop analytical approaches to handle large problems approaches to handle large problems systematically.systematically.
Production flow analysisProduction flow analysis involves four involves four stagesstages::
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Machine - Component Machine - Component Group AnalysisGroup Analysis
Example: Consider a problem of 4 machines Example: Consider a problem of 4 machines and 6 parts. Try to group them.and 6 parts. Try to group them.
Machines 1 2 3 4 5 6
M1 1 1 1
M2 1 1 1
M3 1 1 1
M4 1 1 1
Components
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Machine - Component Machine - Component Group AnalysisGroup Analysis
Machines 2 4 6 1 3 5
M1 1 1 1
M2 1 1 1
M3 1 1 1
M4 1 1 1
Components
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Machine - Component Machine - Component Group AnalysisGroup Analysis
SolutioSolutionn
Rank Order Clustering Rank Order Clustering AlgorithmAlgorithm
Rank Order Clustering AlgorithmRank Order Clustering Algorithm is a simple algorithm used to form is a simple algorithm used to form machine-part groups.machine-part groups.
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Step 1: Assign binary weight and Step 1: Assign binary weight and calculate a decimal weight for each calculate a decimal weight for each row and column using the following row and column using the following formulas:formulas:
Decimal we
Decimal we bpjn p
ight for row i = b
ight for column j =
ipm-p
p=1
m
p=1
n
2
2
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Rank Order Clustering Rank Order Clustering AlgorithmAlgorithm
Step 2: Rank the rows in order of Step 2: Rank the rows in order of decreasing decimal weight values.decreasing decimal weight values.
Step 3: Repeat steps 1 and 2 for Step 3: Repeat steps 1 and 2 for each column.each column.
Step 4: Continue preceding steps Step 4: Continue preceding steps until there is no change in the until there is no change in the position of each element in the row position of each element in the row and the column.and the column. 5757
Rank Order Clustering Rank Order Clustering AlgorithmAlgorithm
Example:Example:Consider a problem of 5 machines and 10 parts. Try Consider a problem of 5 machines and 10 parts. Try to group them by usingto group them by using Rank Order Clustering Rank Order Clustering Algorithm.Algorithm.
Machines 1 2 3 4 5 6 7 8 9 10
M1 1 1 1 1 1 1 1 1 1
M2 1 1 1 1 1
M3 1 1 1 1
M4 1 1 1 1 1 1
M5 1 1 1 1 1 1 1 1
Components
Table 1
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Rank Order Clustering Rank Order Clustering AlgorithmAlgorithm
Machines 1 2 3 4 5 6 7 8 9 10 Decimalequivalent
M1 1 1 1 1 1 1 1 1 1 1007
M2 1 1 1 1 1 451
M3 1 1 1 1 568
M4 1 1 1 1 1 1 455
M5 1 1 1 1 1 1 1 1 1020
29 28 27 26 25 24 23 22 21 20Binary weight
Components
Table 2
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Rank Order Clustering Rank Order Clustering AlgorithmAlgorithm
Binaryweight
Machines 1 2 3 4 5 6 7 8 9 10
24 M5 1 1 1 1 1 1 1 1
23 M1 1 1 1 1 1 1 1 1 1
22 M3 1 1 1 1
21 M4 1 1 1 1 1 1
20 M2 1 1 1 1 1Decimalequivalent 28 27 27 27 28 20 28 26 11 11
29 28 27 26 25 24 23 22 21 20Binary weight
Components
Table 3
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Rank Order Clustering Rank Order Clustering AlgorithmAlgorithm
Binaryweight
Machines 1 5 7 2 3 4 8 6 9 10 Decimalequivalent
24 M5 1 1 1 1 1 1 1 1 1020
23 M1 1 1 1 1 1 1 1 1 1 1019
22 M3 1 1 1 1 900
21 M4 1 1 1 1 1 1 123
20 M2 1 1 1 1 1 115Decimalequivalent 28 28 28 27 27 27 26 20 11 11
29 28 27 26 25 24 23 22 21 20
Binary weight
Components
Table 4
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Rank Order Clustering Rank Order Clustering AlgorithmAlgorithm
• R/O clustering oscillations indicating need of machine replication (happens often!)
• Presence of Outliers and/or Voids in the finished clusters
• Outliers indicate the need of machine replication
• Voids indicate ‘skipped’ machines in a cell
• Generally speaking, these clustering algorithms are designed to convert existing routes for facility re-organization
• They require a previous engineering study to be performed to develop a series of routers on a core sample of parts that represent most of the production in the shop
Rank Order Clustering Rank Order Clustering AlgorithmAlgorithm
The ROC provides a simple analytical The ROC provides a simple analytical technique that can be easily technique that can be easily computerizedcomputerized
The ROC has fast convergence and The ROC has fast convergence and relatively low computation time relatively low computation time depending on the matrix sizedepending on the matrix size
The fact that ROC uses binary values The fact that ROC uses binary values will impose restrictions on the size of will impose restrictions on the size of the matrix that can be solvedthe matrix that can be solved
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Rank Order Clustering Rank Order Clustering AlgorithmAlgorithm
Most computers have a maximum of Most computers have a maximum of 224848-1 for integer representation, which -1 for integer representation, which means that the maximum number of means that the maximum number of rows and columns is limited to 47 and rows and columns is limited to 47 and columns is limited to 47columns is limited to 47
The algorithm results depend on the The algorithm results depend on the initial matrix arrangementinitial matrix arrangement
The algorithm collects positive entries The algorithm collects positive entries (1s) in the top left-hand corner, leaving (1s) in the top left-hand corner, leaving the rest of the matrix disorganizedthe rest of the matrix disorganized
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Rank Order Clustering Rank Order Clustering AlgorithmAlgorithm
Cluster Identification Cluster Identification Algorithm (CIA)Algorithm (CIA)
Designed to identify disconnected blocks if Designed to identify disconnected blocks if they existthey exist
If there are no disconnected blocks (the matrix If there are no disconnected blocks (the matrix is not mutually separable), the entire matrix is not mutually separable), the entire matrix will form one blockwill form one block
The algorithm begins by masking all columns The algorithm begins by masking all columns that have an entry of 1 in any row (selected that have an entry of 1 in any row (selected randomly), then all rows that have an entry of randomly), then all rows that have an entry of 1 in these columns are masked. This process is 1 in these columns are masked. This process is repeated until all intersecting columns and repeated until all intersecting columns and rows are masked.rows are masked.
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These masked columns and rows are These masked columns and rows are placed in a block and removed from the placed in a block and removed from the matrix removed from the matrix. matrix removed from the matrix.
Then the process of masking starts again Then the process of masking starts again and another block is identified. and another block is identified.
This will continue until all the entries in This will continue until all the entries in the matrix are assigned in blocks and all the matrix are assigned in blocks and all separable blocks are identified separable blocks are identified
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Cluster Identification Cluster Identification Algorithm (CIA)Algorithm (CIA)
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Cluster Identification Cluster Identification Algorithm (CIA)Algorithm (CIA)Example:
Step 1. Select any row i of the incidence matrix and draw a horizontal line hi through it.
Row 3 of the matrix is selected randomly and a horizontal line h3 is drawn.
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Cluster Identification Cluster Identification Algorithm (CIA)Algorithm (CIA)
Step 2. For each entry of 1 crossed by the horizontal line h3
draw a vertical line vj.
Three vertical lines v2, v6, and v7 are drawn
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Cluster Identification Cluster Identification Algorithm (CIA)Algorithm (CIA)
Step 3. For each entry of 1 crossed once by a vertical line vj
draw a horizontal line. A horizontal line h6 is drawn through all the crossed-once entries of the matrix:
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Cluster Identification Algorithm Cluster Identification Algorithm (CIA)(CIA)
Step 4. The preceding steps are repeated until no more crossed once entries are left.
• All the crossed-twice entries are grouped in a block and removed from the matrix.
•Parts 2, 6, 7 and machines 3, 6 are grouped in one block.
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Cluster Identification Algorithm Cluster Identification Algorithm (CIA)(CIA)
The grouped parts and machines are removed from the matrix
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Cluster Identification Cluster Identification Algorithm (CIA)Algorithm (CIA)
Step 5: The above procedure is repeated for the
remaining matrix entries until all entries are grouped
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Cluster Identification Cluster Identification Algorithm (CIA)Algorithm (CIA)
The resulting matrix is as follows:
Arranging Machines in a GT Cell
• After part-machine grouping have been identified by cell formation approaches, the next problem is to organize the machines into the most logical arrangement.
• Hollier Method. This method uses the sums of flow “From” and “To” each machine in the cell. The method can be outlined as follows
1. Develop the From-To chart from part routing data. The data contained in the chart indicates numbers of part moves between the machines in the cell.
2. Determine the “From” and “To” sums for each machine. This is accomplished by summing all of the “From” trips and “To” trips for each machine. The “From” sum for a machine is determined by adding the entries
in the corresponding row.
The “To” sum is found by adding the entries in the corresponding column.
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3. Assign machines to the cell based on minimum “From” or “To” sums. The machine having the smallest sum is selected. If the minimum value is a “To” sum, then the machine is placed at
the beginning of the sequence.
If the minimum value is a “From” sum, then the machine is placed at the end of the sequence.
Tie breaker
If a tie occurs between minimum “To” sums or minimum “From” sums, then the machine with the minimum “From/To” ratio is selected.
If both “To” and “From” sums are equal for a selected machine, it is passed over and the machine with the next lowest sum is selected.
If a minimum “To” sum is equal to a minimum “From” sum, then both machines are selected and placed at the beginning and end of the sequence, respectively
4. Reformat the From-To chart. After each machine has been selected, restructure the From-To chart by eliminating the row and column corresponding to the selected machine and recalculate the “From” and “To” sums.
5. Repeat steps 3 and 4 until all machines have been assigned
Arranging Machines in a GT Cell
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Example of Arranging Machines in a GT Cell
• Suppose that four machines, 1, 2, 3, and 4 have been identified as belonging in a GT machine cell. An analysis of 50 parts processed on these machines has been summarized in the From-To chart presented below. Additional information is that 50 parts enter the machine grouping at machine 3, 20 parts leave after processing at machine 1, and 30 parts leave after machine 4. Determine a logical machine arrangement using Hollier method.
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Example of Arranging Machines in a GT Cell
• First iteration
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Example of Arranging Machines in a GT Cell
• Second iteration with machine 3 removed.
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Example of Arranging Machines in a GT Cell
• Third iteration with machine 2 removed.
• The resulting machine sequence 3 2 1 4
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Example of Arranging Machines in a GT Cell
• The flow diagram for machine cell in the Example is shown below. Flow of parts into and out of the cells has also been included
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Hollier MethodHollier Method
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Hollier MethodHollier Method
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Hollier Method 2 ExampleHollier Method 2 Example
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Resulting machine sequence 3 – 2 – 1 – 4