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  • 7/27/2019 Cellular Manufacturing Systems (1)

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    6/10/20

    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

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