group technology

Advanced Manufacturing Advanced Manufacturing Systems DesignSystems Design

© 2000 © 2000 John W. NazemetzJohn W. Nazemetz

Lecture 5 Topic :Lecture 5 Topic : Group Technology Group Technology

Segment A Topic:Segment A Topic: Definition and Definition and ConceptsConcepts

© 2000 John W. NazemetzSlide 2Computer Integrated

Manufacturing Systems

ADVANCED ADVANCED MANUFACTURING MANUFACTURING SYSTEMS DESIGNSYSTEMS DESIGN

Group Technology Group Technology

Definition and ConceptsDefinition and Concepts



OverviewOverview

• Group TechnologyGroup Technology

– Definitions

– Concepts



Group Technology – Group Technology – Definition (1)Definition (1)

• DefinitionDefinition– Group Technology is an operating

management philosophy based on the recognition that similarities occur in the design and manufacture of discrete parts.

– Group Technology exploits the similarities among attributes of objects for the purpose of performing a known function. The attributes may be physical or process oriented.



Group Technology – Group Technology – Definition (2)Definition (2)

• Alternate Definition (Webster)Alternate Definition (Webster)– Group

• To Combine in a Group, to Assign to a Group, Synonymous with Classify

– Technology• An Applied Science, A Technical Method to

Achieve a Practical Purpose.

– GT => A Technical Method of Group Formation



Group Technology -Group Technology -ApplicationsApplications

• ApplicationsApplications– Design

• Similar Shapes• Similar Processing

– Group Scheduling• Sequence Dependant Set Ups

– Cellular Manufacturing (Decomposition of Manufacturing Problem)• Logical Cells• Physical Cells



Group Technology-Group Technology-BenefitsBenefits

• DesignDesign– Part Standardization

• Reduces Inventories• Reduces Managerial

Complexity

– Access to Manufacturing Process Information

– Increased Designer Productivity

• ManufacturingManufacturing– Increase

Throughput– Reduce Variability– Improve Inventory

Management– Reduce Set Up– Improve Efficiency– Improve Quality– Simplify Procedures– Reduce Tooling



Classification and Classification and Coding (1)Coding (1)

• ClassificationClassification– Grouping of Like Things– Based on Physical or Process

Attributes– Logical and Systematic

• CodingCoding– Shorthand Notation for Complex Ideas



Classification and Classification and Coding (2)Coding (2)• ClassificationClassification

– All - Embracing– Mutually Exclusive– Based on “Permanent” Characteristics– Reflect Users’ Objective and

Nomenclature

• CodingCoding– Set of Symbols to which a Meaning has

been Assigned– Will Database Technology Render

Coding Obsolete?



Group Technology – Group Technology – Grouping Attributes (1)Grouping Attributes (1)• ShapeShape• Form FeaturesForm Features• TreatmentsTreatments• FunctionsFunctions• Size EnvelopesSize Envelopes• ToleranceTolerance



Group Technology – Group Technology – Grouping Attributes (2)Grouping Attributes (2)

• Surface FinishSurface Finish• Material Type/ConditionMaterial Type/Condition• QuantityQuantity• Next AssemblyNext Assembly• Raw Material FormRaw Material Form• … … (Others Based on (Others Based on

Application/User)Application/User)



Group Technology – Group Technology – Grouping MethodsGrouping Methods

• Visual Inspection of Existing PartsVisual Inspection of Existing Parts– Usually Done As Parts are Made

• Using Codes Defined During DesignUsing Codes Defined During Design– Pattern Recognition (Similarity)

• Features• Processes

• QueryQuery– Characteristics in Database

• Derived Attributes• Additionally Input Attributes



Monocode (1)Monocode (1)

• Additional Digits Amplifies Additional Digits Amplifies Previous DigitPrevious Digit– Digit 1 = 1 -> Component

•Digit 2 = 4 ->Cylinder– Digit 3 = Diameter, Digit 4 = Length, …

•Digit 2 = 5 -> Rectangular– Digit 3 = Length, Digit 4= Width,– Digit 5 = Height, etc




• Additional Digits Amplifies Additional Digits Amplifies Previous DigitPrevious Digit– Digit 1 = 2 -> Assembly

•Digit 2 = ->Assembly Method– 1 = Mechanical

•Digit 3 = -> Assembly Parameter– IF Digit 2 =1, Digit 3= Type of Fastener– IF Digit 2 = 2 (Weld), Digit 3 = Type (Arc,

…)




• Additional Digits Amplifies Additional Digits Amplifies Previous DigitPrevious Digit– Large Number of Combinations

Possible•N1 x N2 x N3 x N4 x … Nn

– Difficult for Human Interpretation– Cannot Sort on Single (Internal)

Digit•Meaning Dependant on Preceding Digit



PolycodePolycode

• Each Digit Has Single MeaningEach Digit Has Single Meaning– Combinations Possible

•N1 + N2 + N3 + N4 + … + Nn

– Block Code – Not Difficult for Human Interpretation

– Can Sort on Single (Internal) Digit•Meaning Independent of Preceding

Digit

– Long Codes May Result



Mixed CodesMixed Codes

• Combines Mono- and Poly- Combines Mono- and Poly- CodingCoding– Attempt to Shorten Code while

Allowing a Larger Number of Possibilities



Is Coding Obsolete? (1)Is Coding Obsolete? (1)

• Should Actual Data be Used vs. Should Actual Data be Used vs. a Code Which Inexactly a Code Which Inexactly Represents It?Represents It?– Attributes can be Derived and

Stored Automatically• I.e., Largest Dimension = Length•Use Database Search Engine/Query

to Find Groups – Dynamic – Not Predefined, Flexible



Is Coding Obsolete? (2)Is Coding Obsolete? (2)

• Not Quite YetNot Quite Yet– Coding Is Efficient– Legacy Systems Use Coding– Coding Embedded in Corporate

Culture



Using Database Using Database Elements for Grouping Elements for Grouping

(1)(1)• ProblemsProblems

– Speed of Search– Requirement to “Exact Match”,

Control of Alphanumeric Elements•Synonyms

– Is 1020 same as 1020 Steel?

•Spelling– Is ALUM same as Alum same as

Aluminium?

•Confusion– Is 305 a Stainless or a Tool Steel?




(2)(2)• SolutionsSolutions

– Indexing Data to Speed Search•Quicker to Search Numeric Fields

– Use Multiple Stage Searches (Code?)

– Requirement to “Exact Match”, Control of Alphanumeric Elements•Use Drop-Down Selections to Control

Input (Must be all-inclusive)•Can Allow Editable Drop Downs But

Maintenance is Required.




(3)(3)MaintenanceMaintenance

– Make System Data Driven•No “Hard Coding”

– Higher Initial Cost– Lower Maintenance

– Requires Diligence and Discipline




Segment A Topic:Segment A Topic: Definition and Definition and ConceptsConcepts

END OF SEGMENTEND OF SEGMENT




Segment B Topic:Segment B Topic: Example Example





Example - GTSSExample - GTSS



GTSSGTSS

• Group Technology Selection SystemGroup Technology Selection System– Developed for DLA to Assist in

Acquisition– Developed as Part of the CATT Program



Overall MissionOverall Mission• Facilitate the Part Acquisition ProcessFacilitate the Part Acquisition Process• Identify Manufacturers with Particular Identify Manufacturers with Particular

CapabilitiesCapabilities• Grouping of Parts by their SimilaritiesGrouping of Parts by their Similarities• Enable Mapping of Manufacturers to Enable Mapping of Manufacturers to

Individual or Groups of Parts Using Individual or Groups of Parts Using Group Technology and Information Group Technology and Information TechnologiesTechnologies



Project InitiativeProject Initiative• Create National and Local Versions of Create National and Local Versions of

Part and Vendor Information SystemPart and Vendor Information System• DLA Deployment (DSCR, DSCC)DLA Deployment (DSCR, DSCC)

– SCRA, DSCC, DSCR, OSU– Captures only manufacturers with CAGE

codes

• Oklahoma DeploymentOklahoma Deployment– CATT -- CDS, GTI/ICI Group, OKC-ALC– Captures Oklahoma manufacturers



GTSS I nformation Flow

GTSSValue Engr. Division

TDPsvia JEDMICS

VendorData

Partsto be codedor procured

FSC, NIIN, WSC,Part Name, Part No.,Cage Code, Dwg No./Rev.

High-Level Inputs

SAMMS

File of GT coded

Parts

ReportsGroupingMapping

High-Level Outputs

SAMMS

Update

VendorDatabase



System FunctionsSystem Functions

• NSN Data EntryNSN Data Entry– Identification Data– GT Code Generation

• Vendor Data EntryVendor Data Entry– Identification Data– Capabilities

• GroupingGrouping• MappingMapping

• Data ManipulationData Manipulation– Entry/Edit Data– Error Checking– File Import/Export– Data Display (Search)– Data Display (Filter)– Data Display (Sort)– Vendor Queries– Report Generation



Systems Design Systems Design ConceptsConcepts

• COTS SoftwareCOTS Software– Windows 95– PowerBuilder– Oracle

• SecuritySecurity– Passwords– User Levels

• Data DrivenData Driven– Ease of Maintenance

• Graphical InterfaceGraphical Interface– Easy to Use– Intuitive– Simple

• Group Technology Group Technology – Part Feature Based Part

and Vendor Codes

• On-Line HelpOn-Line Help– Easy to Use



Data Base Design Data Base Design ConceptsConcepts

• Balance Data Detail Level, DB SizeBalance Data Detail Level, DB Size– Longer/Deeper Code

• Better Data Resolution, But Data Base Grows Exponentially

– Use Auxiliary Fields to Reduce DB Size

• Hybrid Group Technology CodeHybrid Group Technology Code– First Positions used to Define Rest of

Code– Same Code for Vendors and Parts

• Parts have a Single Code• Vendors have Multiple Codes



Data Base Design Data Base Design Concepts Concepts (cont.)(cont.)

• Impact of Code Length/Depth on DBImpact of Code Length/Depth on DB– Number of categories is product of number

of positions and number of possible selections

– Example: For a 10 position code with each code position having 5 possible selections, 9,765,625 possible combinations/categories• While a part would have only one code, a vendor

who can make everything has nearly 10 million.




• Impact of Auxiliary FieldsImpact of Auxiliary Fields– If data is stored in an auxiliary field

rather than a code digit, DB size is reduced

– Example: if auxiliary field were used to reduce a 10 position, 5 selection code to 7 positions, 5 selections, the number of possible combinations is 78,125, not 9,765,625




• Data in GT CodeData in GT Code– Material Type

[2]– Shape [4]– Raw Mat’l Form [4]– Alt. Mat’l Form [4]– Size [5,30]– Tolerances [4]– Quality

[4]• approximately

53,760 possible categories

• Data in Auxiliary Data in Auxiliary FieldsFields– Material Spec Type– Material Spec– Plating– Treatment– Coating– Material Name

• if these fields in code @ 10 selections each, one half trillion categories



GT Code Design GT Code Design ConceptsConcepts

• First Two Code Positions Are FixedFirst Two Code Positions Are Fixed– Part Type (Initial Project Scope)

• Mechanical Piece Part• Mechanical Subassembly

– Shape• Prismatic, Cylindrical, Sculptured, Gears• Not Used for subassemblies



GT Code Design GT Code Design Concepts Concepts (cont.)(cont.)

• Remaining Code ElementsRemaining Code Elements– Piece Parts

• Size • Tolerances• Raw Material Form• Alt. Raw Material Form• Quality Req.

– Subassemblies• Kitted/Assembly• Weight• Size• Fabrication/

Machining• Tolerances• Quality Req.



GUI Design ConceptsGUI Design Concepts• Follows WINDOWS StandardsFollows WINDOWS Standards

– Main Toolbar w/Dropdown menus– Relocatable Icon Toolbar– Right Mouse Button Activated

Response Windows– Context Sensitive Help Available– Dynamic Error Checking



Summary/AssessmentSummary/Assessment• ConceptsConcepts

– Theoretically Sound– Method of Coding Manufacturers Was

Awkward

• ProblemsProblems– No Funds for Legacy Part Coding

• UseUse– Used to Identify Suppliers




Segment B Topic:Segment B Topic: Example Example

END OF SEGMENT END OF SEGMENT




Segment C Topic:Segment C Topic: Grouping – Grouping – Analysis MethodsAnalysis Methods





Grouping – Analysis MethodsGrouping – Analysis Methods



OverviewOverview• Grouping/Analysis MethodsGrouping/Analysis Methods

– Production Flow Analysis• Rank Order Clustering• Similarity Indexes

– Single Linkage– Weighted (Production Volume)

• Mathematical Programming

• NOTE: The Following Slide Materials are NOTE: The Following Slide Materials are From Singh, From Singh, Systems Approach to Systems Approach to Computer Integrated Design and Computer Integrated Design and ManufacturingManufacturing, p. 490-499., p. 490-499.



Production Flow Production Flow AnalysisAnalysis



ProductioProductionn

Flow Flow AnalysisAnalysis

Matrix

Manipulation

Row and ColumnSorting



Rank Order Clustering Rank Order Clustering (1)(1)



Rank Order Clustering (2)Rank Order Clustering (2)



Rank Order Clustering (3)Rank Order Clustering (3)



Single Linkage Cluster Single Linkage Cluster Algorithm (1)Algorithm (1)



Siefoddini and WolfeSiefoddini and Wolfe

• Considers Production Volume Considers Production Volume (Weighted Average)(Weighted Average)



Exceptional Parts and Exceptional Parts and Bottleneck MachinesBottleneck Machines

• Practical Approach to Problem of Practical Approach to Problem of Costly EquipmentCostly Equipment

• Allow InterCell MovementAllow InterCell Movement• EliminationElimination

– Generate Alternate Processing Plans– Duplicate Machines– Subcontracting Operations

• Still Has InterCell Transfers



Alternate Cell Alternate Cell Configurations (SLCA)Configurations (SLCA)



Alternate Cell Alternate Cell Configuration AnalysisConfiguration Analysis

Why Why

CellCell

One?One?



Mathematical ModelsMathematical Models

• Cell Design with Known Part FamiliesCell Design with Known Part Families– Minimize Machine Investment

• Cell Design with Unknown Part Cell Design with Unknown Part FamiliesFamilies– Minimize Machine Investment– Constrains Maximum Number of Machines

in Cell

• Cell Design With Unknown Part Cell Design With Unknown Part Families, Key MachinesFamilies, Key Machines– Minimize Investment,

Movement/Backtracking



Grouping EfficacyGrouping Efficacy

• Method for Evaluating Goodness of Method for Evaluating Goodness of FitFit



Group TechnologyGroup Technology

Discussion Topic C:Discussion Topic C: Grouping -- Grouping -- Analysis MethodsAnalysis Methods

END OF SEGMENTEND OF SEGMENT

group technology

Documents

code positions

position code

code digit

selection code

impact of code lengthdepth

rest of codesame code

possible categoriesdata

product of number