Cellular Manufacturing Systems (1)

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<ul><li><p>7/27/2019 Cellular Manufacturing Systems (1)</p><p> 1/22</p><p>6/10/20</p><p>Cellular Manufacturing</p><p>Sections:</p><p>1. Part Families2. Parts Classification and Coding</p><p>3. Production Flow Analysis</p><p>4. Cellular Manufacturing</p><p>5. Applications in Group Technology</p><p>6. Quantitative Analysis in CellularManufacturing</p><p>Recap</p><p> GT</p><p> Define Relation with lay out</p><p> Types</p><p> Visual</p><p> Coding</p><p> PFA</p><p>Cellular Manufacturing Systems</p><p>Cellular Manufacturing</p><p>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</p><p> Typical objectives of cellular manufacturing: To shorten manufacturing lead times</p><p> To reduce WIP</p><p> To improve quality</p><p> To simplify production scheduling</p><p> To reduce setup times</p><p>Composite Part Concept</p><p>A composite partfor a given family is a hypothetical partthat includes all of the design and manufacturingattributes of the family</p><p> In general, an individual part in the family will havesome of the features of the family, but not all of them</p><p> A production cell for the part family would consist ofthose machines required to make the composite part</p><p> Such a cell would be able to produce any familymember, by omitting operations corresponding tofeatures not possessed by that part</p><p>Composite Part ConceptComposite part concept:</p><p>(a) the composite part for a family of machined rotational</p><p>parts, and</p><p>(b) the individual features of the composite part</p></li><li><p>7/27/2019 Cellular Manufacturing Systems (1)</p><p> 2/22</p><p>6/10/20</p><p>Part Features and Corresponding</p><p>Manufacturing Operations</p><p>Design feature Corresponding operation</p><p>1. External cylinder Turning2. Face of cylinder Facing</p><p>3. Cylindrical step Turning</p><p>4. Smooth surface External cylindricalgrinding</p><p>5. Axial hole Drilling</p><p>6. Counter bore Counterboring</p><p>7. Internal threads Tapping</p><p>Machine Cell Designs</p><p>1. Single machine</p><p>-One machine plus supporting fixtures &amp; tooling1. Multiple machines with manual handling</p><p> Often organized into U-shaped layout</p><p>2. Multiple machines with semi-integrated handling</p><p>3. Automated cell automated processing andintegrated handling</p><p> Flexible manufacturing cell</p><p> Flexible manufacturing system</p><p>Machine Cell with Manual Handling</p><p>U-shaped machine cell with manual part handlingbetween machines</p><p>Cell with Semi-Integrated Handling</p><p>In-line layout using mechanized work handlingbetween machines</p><p>Cell with Semi-Integrated Handling</p><p>Loop layout allows variations in part routingbetween machines</p><p>Cell with Semi-Integrated Handling</p><p>Rectangular layout also allows variations in part routingand allows for return of work carriers if they are used</p></li><li><p>7/27/2019 Cellular Manufacturing Systems (1)</p><p> 3/22</p><p>6/10/20</p><p>Four Types of Part Moves in</p><p>Mixed Model Production System Key Machine Concept</p><p> Applies in cells when there is one machine (the</p><p>key machine) that is more expensive orperforms certain critical operations</p><p> Other machines in the cell are supporting machines</p><p> Important to maintain high utilization of keymachine, even if this means lower utilization of</p><p>supporting machines</p><p>Applications of Group Technology</p><p> In product manufacturing</p><p> In product Design</p><p>Manufacturing Applications</p><p>of Group Technology Different ways of forming machine cells:</p><p> Informal scheduling and routing of similar partsthrough selected machines to minimize setups</p><p> Virtual machine cells dedication of certainmachines in the factory to produce part families,but no physical relocation of machines</p><p> Formal machine cells machines are physicallyrelocated to form the cells</p><p> Automated process planning Modular fixtures Parametric programming in NC</p><p>Benefits of Group Technology</p><p>in Manufacturing</p><p> Standardization of tooling, fixtures, and setups isencouraged</p><p> Material handling is reduced Parts are moved within a machine cell rather than the entire</p><p>factory Process planning and production scheduling are</p><p>simplified</p><p> Work-in-process and manufacturing lead time arereduced</p><p> Improved worker satisfaction in a GT cell Higher quality work</p><p>Product Design Applications</p><p>of Group Technology</p><p> Design retrieval systems Industry survey: For new part designs,</p><p> Existing part design could be used - 20%</p><p> Existing part design with modifications 40% New part design required 40%</p><p> Simplification and standardization of designparameters such as tolerances, chamfers,hole sizes, thread sizes, etc.</p><p> Reduces tooling and fastener requirements inmanufacturing</p></li><li><p>7/27/2019 Cellular Manufacturing Systems (1)</p><p> 4/22</p><p>6/10/20</p><p>QuantitativeAnalysisinCellularManufacturing</p><p>Grouping parts and machines by RankOrder Clustering</p><p>Arranging machines in a GT Cell</p><p>CMS and its relationship to Job and Flow Shops:</p><p> We can define the movement in a Job Shop</p><p>(mathematically) this way for any product i: Pr(12)i = Pr(13)i = Pr(14)i = = Pr(1n)I</p><p> While in a Flow Shop:</p><p> Pr(12)i = 1 and Pr(1n)i = 0(n 2)</p><p> In developing CMS manufacturing systems weare trying to make all part flows act like Flow</p><p>shop mathematics!</p><p>Examining a Cell in the CMS:</p><p>NoticeMWormulti-functionalworkersthisteamisresponsibleforallproductionwithintheircell</p><p>CMS and Group Technology (GT) CMS layout are based on recognizing similarities in</p><p>products similarities in geometry, size, materialsand processing requirements</p><p> This similar products are collected Groupedinstead of being treated as individuals</p><p> Leads to product families that visit similarequipment and populate their cells productionschedule</p><p> Simpler setups like in a Job shop can follow and theworkers become multifunctional and responsiblefor all aspects of a product and its quality</p><p> Cells can be scheduled to produce synchronouslybringing the various sub-assemblies in as needed at</p><p>final assembly with greater variety built in</p><p>CMS and Group Technology (GT)CMS and Group Technology (GT)</p><p>NOTE:Step1isCMSafundamentalactioninLEANMFGing</p><p>BuildingtheFACTORYWithAFUTURE</p></li><li><p>7/27/2019 Cellular Manufacturing Systems (1)</p><p> 5/22</p><p>6/10/20</p><p>CMS and Group Technology (GT) Benefits of GT and CMS (Companies Reporting):</p><p> 52%Report reduction in new part design</p><p> 10%Report reduction in #of new drawings thru</p><p>standardization 30%Report reduction in new shop drawings</p><p> 60%Report reduction in IE time</p><p> 20%Report reduction in floor space</p><p> 45%Report reduced scrap</p><p> 80%Report reduced production and quality costs</p><p> 69%Report reduced set-up time (cost)</p><p>Note:ReportedbycompaniesinasurveyofadoptersofGT</p><p>Benefits of GT and CMS (Companies Reporting):</p><p> 70%Report reduced throughput time (even morereport better predictability of delivery)</p><p> 82%Report reduced numbers of overdue orders</p><p> 42%Report reduced raw-materials inventory</p><p> 62%Report reduced WIP</p><p> 60%Report reduced finished goods inventory</p><p> 33%Report increased employee output/time unit(productivity improvement)</p><p>Clustering Techniques: the Fundamental Issue in</p><p>Cell Development</p><p> We cluster parts to build part families</p><p> Part Families visit cells</p><p> Part Families share set-up ideas and equipment(Family Fixtures)</p><p> Part Families follow the same (or similar) processrouting</p><p> These are the ideas and activities that offerreported benefits</p><p>Clustering Techniques: the Fundamental Issue in</p><p>Cell Development</p><p> We cluster Machines to build cells:</p><p> Cells lead to Flow Mathematics</p><p> Cells contain all equipment needed to produce a part</p><p>family Cells allow development of Multi-functional workers</p><p> Cells hold work teams responsible for production andquality They Empowerthe workers</p><p> Empowered to set internal schedules</p><p> Empowered to assign tasks</p><p> Empowered to train and rotate jobs</p><p> Etc, etc, etc</p><p>Building the CMS Facility</p><p>BeforeClustering</p><p>AfterClustering</p></li><li><p>7/27/2019 Cellular Manufacturing Systems (1)</p><p> 6/22</p><p>6/10/20</p><p>Recap</p><p> GT Define Relation with lay out Types</p><p> Visual</p><p> Coding</p><p> PFA QuantitativeAnalysisinCellularManufacturing</p><p> Clustering Method Process Similarity methods Rank Order Method</p><p> Arranging Machines in GT Cell</p><p>Clustering Methods</p><p> Using Process Similarity methods:</p><p> Create Machine Part Matrices</p><p> Compute machine pair wise Similarity Coefficientcomparisons:</p><p> :</p><p>is # of parts (in matrix) visiting</p><p>both machines of the pair</p><p>is # of parts visiting one but not both m achines</p><p>ij</p><p>jjx</p><p>ij</p><p>ij</p><p>ij jj</p><p>here</p><p>x</p><p>xS</p><p>x x</p><p>PartNumber</p><p>MachineID</p><p>X 1 2 3 4 5 6</p><p>A 1 1</p><p>B 1 1</p><p>C 1 1</p><p>D 1 1 1</p><p>E 1 1 1</p><p>Example: Computing Similarity Coefficients:</p><p> Total Number is: [(N-1)N]/2 = [(5-1)5]/2 = 10 Where N-is No. of machines.</p><p> For 25 machines (typical number in a small Job Shop): 300Sijs</p><p> Here they are:</p><p>1.33</p><p>1 2</p><p>00</p><p>0 4</p><p>2.67</p><p>2 1</p><p>AB</p><p>AC</p><p>AD</p><p>S</p><p>S</p><p>S</p><p>Continuing:</p><p>00</p><p>0 5</p><p>00</p><p>0 4</p><p>2.67</p><p>2 1</p><p>00</p><p>0 5</p><p>00</p><p>0 5</p><p>2.67</p><p>2 1</p><p>00</p><p>0 6</p><p>AE</p><p>BC</p><p>BD</p><p>BE</p><p>CD</p><p>CE</p><p>DE</p><p>S</p><p>S</p><p>S</p><p>S</p><p>S</p><p>S</p><p>S</p><p> Here, if the similaritycoefficient is &gt;0.33 consider</p><p>clustering</p><p> This criteria meansclustering:</p><p> A&amp;D, A&amp;B, B&amp;D</p><p> C &amp; E</p><p> De-clustering: A&amp;C, A&amp;E, B&amp;C, B&amp;E and C&amp;D,</p><p>D&amp;E</p><p>Continuing: Examining our Matrix and our freshly</p><p>clustered machine cells, we develop 2 partfamilies:</p><p>For the Cell A/D/B: Part Numbers 2, 3 &amp; 5</p><p>For the Cell C/E: Part Numbers 1, 4 &amp; 6</p><p> 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</p><p> 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</p><p>This is typically one of the cost problems in CMS systems</p></li><li><p>7/27/2019 Cellular Manufacturing Systems (1)</p><p> 7/22</p><p>6/10/20</p><p>Summarizing</p><p>(Process Similarity Method):</p><p> Make Machine/Part Matrix</p><p> Compute Similarity Coefficients Cluster Machines with positive (&gt;.33) Sijs</p><p> Determine Part Families for the clusters (cells)</p><p> Decide if machine replication is cost effective</p><p> Re-layout facility and Cross Train workforce</p><p> Start counting your new found cash</p><p> Court customers to grow part families on Cell-by-Cell basis</p><p>Other Clustering Methods:</p><p> Rank order Clustering</p><p> This method automates the cluster study by computing</p><p>Binary weights from a machine part matrix It orders parts and machine cells automatically by</p><p>structuring and computing the matrix with binary weights</p><p> It implies a computer algorithm for solving the clusteringproblem</p><p> It may not solve if machines are needed by more than onefamily forces intelligence in application and hand</p><p>scanning after several ordering iterations</p><p>Rank Order Clustering Method:</p><p>Steps:1. For each row of the machine/part matrix (M/P/M) read the pattern of cell</p><p>entries as a binary word. Rank the rows by decreasing binary value.Equal values stay in same order.</p><p>2. Ask if newly ranked rows in the matrix are the same as previous order? Yes (STOP) No (continue)</p><p>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</p><p>4. Are current column weights the same as current column order? Yes(STOP), No (continue)</p><p>5. Re-form the matrix column order per rank order (highest to left) andreturn to#1.</p><p>Lets try it with our earlier problem:</p><p>PartNumber</p><p>MachineID</p><p>X 1 2 3 4 5 6</p><p>A 1 1</p><p>B 1 1</p><p>C 1 1</p><p>D 1 1 1</p><p>E 1 1 1</p><p>Step 1:</p><p>PartNumbers D.Equiv Rank</p><p>MachineID</p><p>1 2 3 4 5 6</p><p>B.Wt: 25 24 23 22 21 20</p><p>A 1 1 23+21=10 5</p><p>B 1 1 24+23=24 4</p><p>C 1 1 25+22=36 2</p><p>D 1 1 124+23+21=</p><p>263</p><p>E 1 1 125+22+20=</p><p>371</p><p>Step2:MustReorder!</p><p>Step 3:</p><p>PartNumber</p><p>B.WT. 1 2 3 4 5 6</p><p>MachineID</p><p>E 24 1 1 1</p><p>C 23 1 1</p><p>D 22 1 1 1</p><p>B 21 1 1</p><p>A 20 1 1</p><p>D.Equiv24+23</p><p>=2422+21=6</p><p>22+21+20=7</p><p>24+23=24</p><p>22+20=5</p><p>24=16</p><p>Rank 1 5 4 2 6 3</p><p>Step4:MustReorder</p></li><li><p>7/27/2019 Cellular Manufacturing Systems (1)</p><p> 8/22</p><p>6/10/20</p><p>Back at Step 1:</p><p>PartNumber D.Eqv Rank</p><p>1 4 6 3 2 5</p><p>BWt: 25 24 23 22 21 20</p><p>MachineID</p><p>E 1 1 125+24+23=56</p><p>1</p><p>C 1 125+24=48</p><p>2</p><p>D 1 1 122+21+20</p><p>=73</p><p>B 1 1 22+21=6 4</p><p>A 1 1 22+20=5 5</p><p>Orderstaysthesame:STOP!</p><p>GreatClusterResult! Issues in Clustering:</p><p> R/O clustering oscillations indicating need of machinereplication (happens often!)</p><p> Presence of Outliers and/or Voids in the finishedclusters</p><p> Outliers indicate the need of machine replication</p><p> Voids indicate skippedmachines in a cell</p><p> Generally speaking, these clustering algorithms aredesigned to convert existing routes for facility re-organization</p><p> 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</p><p>Alternative means to Develop Cells/Families:</p><p> Most often companies rely on Classificationand Coding (C&amp;C) systems for analyzing theirpart mix</p><p> These codes can be general purpose orcompany specific General Purpose:</p><p> Opitz is a german developed code for machined parts(see over)</p><p> KC1, KC2 and KK1 systems Japanese government labbased codes for machined parts</p><p> Brish a british developed code for general material use</p><p> Foundry codes have been developed by several groups(see Lindeke &amp; Rubinovich, 1987 in USA)</p><p>Examining Opitz Code:</p><p>Examining Opitz Code:</p><p>ThisFormcodeistheOpitzCodeSolutiononthisshaft-likepart</p><p>Examining Opitz Code:</p></li><li><p>7/27/2019 Cellular Manufacturing Systems (1)</p><p> 9/22</p><p>6/10/20</p><p>Alternative means to Develop Cells/Families:</p><p> They can be company specific</p><p> If so, they are typically hierarchical and list importantcharacteristics of the part/process mix, physical</p><p>characteristics like size, geometric features, or</p><p>material, etc.</p><p> Since they are specific they tend to be more accuratein building part families</p><p>Alternative means to Develop Cells/Families:</p><p> Using GT Classification and codingsystems, parts are coded by experts at</p><p>the company</p><p> The newly coded part is used to searchexisting production databases forsimilarly coded products</p><p> The new part is assigned to the family itmost closely matches</p><p> Its routing is thus set and only minorvariation needs to be considered</p><p> Using specific digits, a company cantarget marketing in certain areas of theirproduct mix</p><p>Alternative means to Develop Cells/Families:</p><p> In a greenfield shop, managers candevelop facility designs (in the formof reasonable cells) by selectingreasonable seed parts as suggestedby their GT C&amp;C system</p><p> These seeds can be used to buildrouters and, hence appropriatemachine clusters</p><p> Using GT C&amp;C systems, processclusters evolve from parts as opposedto clustering evolving by process</p><p>Fixturing</p><p> Fixturingis a means to speed up partloading and increase accuracy of machine</p><p>and mfg. processes</p><p> These are tools that:</p><p> Locate the work for geometric control ofvarious DOF</p><p> May also provide a means to guide thetooling used to perform the operations (Jigs)</p><p> Before being used these tool must beaccurately placed on the machine often a</p><p>time consuming task since their placement</p><p>tolerance must be 10x better than part</p><p>tolerance!</p><p>Fixturing</p><p> In CMS, it is often possible to build Family Fixtures</p><p> These are fixtures that can be shared among all theparts in the family (because they are similar</p><p>geometrically and by mfg. process) thus reducingtime to set-up any part in the family</p><p> The Family Fixture is generic and may (likely) requirethe addition of specific change pieces for different</p><p>members of the family but definitely not different</p><p>fixtures.</p><p>Fixturing</p><p> Example of Cost Savings:Shop cost is Rs. 50/hour</p><p>Hand setup is 2 minutes/piece (lot is 400parts)</p><p>Setup on Fixture is 0.03 min/partSaving of 1.97 min = .033 hr = Rs.1.64/part</p><p> If machine takes 5 minutes/part, Production rate increasesfrom8.57 parts/hour to 11.93 parts/hr almost...</p></li></ul>