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

    1/22

    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

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

    2/22

    6/10/20

    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

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

    3/22

    6/10/20

    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

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

    4/22

    6/10/20

    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

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

    5/22

    6/10/20

    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

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

    6/22

    6/10/20

    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

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

    7/22

    6/10/20

    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

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

    8/22

    6/10/20

    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:

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

    9/22

    6/10/20

    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

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

    10/22

    6/10/20

    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!

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

    11/22

    6/10/20

    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

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

    12/22

    6/10/20

    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

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

    13/22

    6/10/20

    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

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

    14/22

    6/10/20

    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

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

    15/22

    6/10/20

    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

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

    16/22

    6/10/20

    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

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

    17/22

    6/10/20

    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

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

    18/22

    6/10/20

    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)

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

    19/22

    6/10/20

    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

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

    20/22

    6/10/20

    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

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

    21/22

    6/10/20

    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

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

    22/22

    6/10/20

    Computer aided process control


Top Related