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FACILITY LAYOUT

MODELING AND ANALYSIS OF MANUFACTURING SYSTEMS Session 9 FACILITY LAYOUT E. Gutierrez-Miravete Spring 2001. FACILITY LAYOUT. THE ARRANGEMENT OF MANUFACTURING RESOURCES IN A PLANT. COMMENTS. WHICH RESOURCES SHOULD BE ADJACENT?

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FACILITY LAYOUT

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  1. MODELING AND ANALYSIS OFMANUFACTURING SYSTEMS Session 9FACILITY LAYOUTE. Gutierrez-MiraveteSpring 2001

  2. FACILITY LAYOUT THE ARRANGEMENT OF MANUFACTURING RESOURCES IN A PLANT

  3. COMMENTS • WHICH RESOURCES SHOULD BE ADJACENT? • GOAL: TO PRODUCE A BLOCK PLAN SHOWING THE RELATIVE POSITIONING OF ALL DEPARTMENTS • CAN CAD HELP?

  4. CRITERIA FOR BLOCK PLAN EVALUATION • MINIMIZATION OF MATERIAL HANDLING COST (FREQUENCY AND LENGTH OF MOVES) • MINIMIZATION OF THROUGHPUT AND WIP • SIMPLIFICATION OF MATERIAL CONTROL AND SCHEDULING • REDUCTION IN AISLE SPACE

  5. SOLVING THE FACILITY LAYOUT PROBLEM • OFTEN VIA DETERMINISTIC MODELS • DESIRABLE FEATURES OF SOLUTIONS • FLEXIBILITY • MODULARITY • MAINTAINABILITY • RELIABILITY • EMPLOYEE MORALE

  6. THE SPINE APPROACH TO FACILITY DESIGN • SPINE: CENTRAL CORE OR PASSAGEWAY TO CONDUCT MATERIAL FLOW • DEPARTMENTS EXPAND OUT FROM CENTRAL CORE • UTILITIES: CARRIED OVERHEAD • MATERIAL STORAGE: ALONG SPINE

  7. FACILITY LAYOUT PROBLEM AND QUESTIONS • HOW TO ASSIGN EACH DEPARTMENT TO A SPECIFIC LOCATION IN THE FACILITY? • IS THERE A DOMINANT FLOW PATTERN IN THE PROCESS? • HOW CAN FLOW DOMINANCE BE MEASURED?

  8. FLOW DOMINANCE • CONSIDER DEPARTMENTS i AND j OUT OF A SET M • HANDLING SYSTEM COST hij • FLOW fij

  9. FLOW COST PARAMETER • WEIGHTS FOR MATERIAL FLOW BETWEEN DEPARTMENTS i AND j (FLOW COST PARAMETER) wij = fij hij

  10. STATISTICS OF wij • AVERAGE OF COST FLOW PARAMETER wave = ij wij /M2 • STANDARD DEVIATION OF COST FLOW PARAMETER (FLOW DOMINANCE MEASURE)  = [ij (wij2 - M2 wave2)/(M2-1)]1/2

  11. FLOW DOMINANCE MEASURE f =  / wave • UPPER BOUND ( ONE wij DOMINATES) • LOWER BOUND (ALL wij ARE EQUAL) • See Eqns 7.3, Table 7.1 and Example 7.1

  12. LAYOUT PROBLEMS VS LOCATION PROBLEMS • LAYOUT: MACHINES OCCUPY SPACE • LOCATION: MACHINES ARE POINTS

  13. DISTANCE METRICS (Fig. 7.3) • RECTILINEAR DISTANCE • EUCLIDEAN DISTANCE • lp NORM dij = [ |xi - xj|p + |yi - yj|p ]1/p • ADJACENCY INDICATOR ij

  14. SYSTEMATIC LAYOUT PLANNING

  15. STEPS IN SYSTEMATIC LAYOUT PLANNING (Fig 7.4) STEP 0: DATA COLLECTION STEP 1: FLOW ANALYSIS STEP 2: QUALITATIVE ASPECTS STEP3: RELATIONSHIP DIAGRAM STEP 4: SPACE REQUIREMENTS STEP 5: SPACE AVAILABILITY STEP 6: SPACE RELATIONSHIP DIAGRAM STEPS 7&8: MODIFYING CONSIDERATIONS & LIMITATIONS STEP 9: EVALUATION

  16. STEP0: DATA COLLECTION • PRODUCT (WHAT) • QUANTITY (HOW MUCH) • ROUTING (HOW) • SUPPORT SERVICES (WITH WHAT) • TIMING/TRANSPORT (WHEN)

  17. S0: DATA COLLECTION • PARETO CHARTS (Fig 7.5) • WHAT PERCENT OF ITEMS CONSTITUTE THE BULK OF DEMAND? • WHAT ARE OBJECTIVE ESTIMATES OF SPACE REQUIREMENTS?

  18. STEP 1: FLOW ANALYSIS • TO SPECIFY PHYSICAL WORKCENTERS WHICH WILL BE SPATIALLY ARRANGED • DEPARTMENT DEFINITIONS BASED AROUND PRODUCTS, PROCESSES OR CELLS OF SIMILAR PARTS • FLOW VOLUMES AND PATTERNS ESTABLISHED

  19. S1: FLOW ANALYSIS • OPERATION PROCESS CHARTS (Fig 7.6) • MAJOR OPERATIONS • INSPECTIONS • MOVES • STORAGES • FLOW PROCESS CHARTS (Fig 7.7) • FLOW PATTERNS BETWEEN DEPARTMENTS (Figs 7.8, 7.9, 7.10)

  20. S1: FLOW ANALYSIS • QUANTITATIVE FLOW DATA VIA FROM-TO CHARTS (See Table 7.2) • HOW CAN THE TOTAL FLOW VOLUME BETWEEN WORKCENTERS BE OBTAINED? • HOW CAN THE TOTAL COST BE OBTAINED?

  21. S1: FLOW ANALYSIS • COST OF MATERIAL MOVEMENT FROM WORKCENTER i TO j cij = wij dij • TOTAL COST C = ij cij

  22. S1: FLOW ANALYSIS.FROM-TO CHARTS (Table 7.2) • FLOW VOLUMES • MOVEMENT COST • DISTANCE BETWEEN WORKCENTERS

  23. S1: FLOW ANALYSIS.BASIC FLOW PATTERNS • STRAIGHT-LINE • U-SHAPED • S-SHAPED • W-SHAPED • Fig 7.8

  24. S1: FLOW ANALYSIS.FLOW PATTERNS • PLANT STRAIGHT SPINE-DEPARTMENT U PATTERN (Fig 7.9) • PLANT U SPINE - DEPARTMENT U • ASSEMBLY FLOW PATTERNS (Fig 7.10) • KEY: DESIGN A RATIONAL FLOW PATTERN THAT AVOIDS CONFUSION AND INTERFERENCE

  25. STEP 2: QUALITATIVE CONSIDERATIONS OFTEN, IMPORTANT INFORMATION CAN NOT BE QUANTIFIED. • RECEIVING AND SHIPING NEEDING TO SHARE COMMON FACILITIES • PURCHASING AND ENGINEERING NEEDING TO COMMUNICATE • DELICATE TESTING NEEDING TO BE FAR FROM HEAVY VIBRATION

  26. S2: QUALITATIVE DATA • REL CHARTS (Fig 7.11; Table 7.2) • RATE THE DEGREE OF DESIRABILITY OF LOCATING TWO DEPARTMENTS ADJACENT (A,E,I,O,U,X)

  27. STEP 3: RELATIONSHIP DIAGRAM A RELATIONSHIP DIAGRAM COMBINES QUANTITATIVE AND QUALITATIVE INFORMATION TO INITIATE THE DETERMINATION OF RELATIVE LOCATION OF FACILITIES (Fig 7.12)

  28. Fig. 7.12 S&R XT PS AT PC IC

  29. S3: RELATIONSHIP DIAGRAM 1.- DEPARTMENTS REPRESENTED BY SQUARE TEMPLATES 2.- TEMPLATES ARRANGED IN LOGICAL ORDER 3.- TEMPLATES CONNECTED BY LINES COMMUNICATING THE RELATIONSHIP BETWEEN DEPARTMENT PAIRS 4.- ITERATE

  30. S3: RELATIONSHIP DIAGRAM TWO BASIC STEPS IN HEURISTICS • CONSTRUCTION: DETERMINING THE INITIAL ARRANGEMENT OF TEMPLATES • IMPROVEMENT: SEARCH FOR BETTER ARRANGEMENTS THAN THE INITIAL CONSTRUCTION

  31. S3: REL DIAGRAM. CLOSENESS RATING • ADJACENCY FUNCTION Vij • TOTAL CLOSENESS RATING (TCR) TCRi = j Vij • WHAT IS THE MEANING OF A LARGE VALUE OF TCRi ? • WHERE SHOULD A DEPARTMENT WITH LARGE TCRi BE LOCATED?

  32. S3: REL DIAGRAM. CONSTRUCTION 1.- CALCULATE TCRi FOR ALL DEPARTMENTS AND RANK FROM HIGHEST TO LOWEST 2.- PLACE HIGHEST RANKED DEPARTMENT AT CENTER 3.- ADD DEPARTMENTS ITERATIVELY SUCH THAT THE ADJACENCY SCORE (OR DISTANCE) IS MAXIMAL/MINIMAL • See Example 7.2 and Fig. 7.13

  33. S3: REL DIAGRAM. IMPROVEMENT • IS THE INITIAL CONSTRUCTION OPTIMAL? • WHAT IS A k-OPT SOLUTION? • CRAFT : COMPUTER BASED IMPROVEMENT PROCEDURE • STEEPEST DESCENT PAIRWISE EXCHANGE • PAIRS ARE SWITCHED WHICH LEAD TO THE LARGEST IMPROVEMENT

  34. S3: REL DIAGRAM. IMPROVEMENT • PROSPECTIVE DEPARTMENTS FORM A GRID OF EQUAL SIZED SQUARES • A FEASIBLE SOLUTION TO THE LAYOUT PROBLEM IS THE ASSIGNMENT OF GRID SQUARES TO DEPARTMENTS (THE a VECTOR) a = (a1,a2,a3,...,aM)

  35. S3: REL DIAGRAM. IMPROVEMENT • NOW TRY EXCHANGING DEPARTMENTS u AND v . WHAT IS THE COST INVOLVED IN GOING FROM LAYOUT a TO a’? Cuv(a) = C(a) - C(a’) • WHAT IS THE CHANGE IN ADJACENCY MEASURE? (Example 7.3 and Fig. 7.14)

  36. STEP 4: SPACE REQUIREMENTS • USE OF INDUSTRIAL STANDARDS • ROUGH SKETCHES + LOCAL STANDARDS • USE OF CURRENT SPACE NEEDS • USE OF X SQUARE FEET PER UNIT PRODUCED

  37. STEP 5: SPACE AVAILABILITY • EXISTING FACILITY • NEW FACILITY • GOAL: FIND THE MINIMUM SPACE REQUIRED

  38. STEP 6: SPACE RELATIONSHIP DIAGRAM • DEPARTMENTS OFTEN HAVE DIFFERENT SIZES! • A SPACE RELATIONSHIP DIAGRAM REPLACES THE EQUAL SIZE TEMPLATES OF A RELATIONSHIP DIAGRAM WITH TEMPLATES OF SIZE PROPORTIONAL TO ACTUAL SPACE REQUIREMENTS (Fig 7.15; Table 7.3)

  39. S 6: SWITCHES IN A SRD • IF DEPARTMENTS ARE OF EQUAL SIZE, SWAP GRID SQUARES • IF DEPARTMENTS ARE ADJACENT AND OF DIFFERENT SIZE, SELECT ENOUGH GRID SQUARES FROM LARGE DEPT FARTEST FROM SMALL ONE, THEN MOVE SMALL DEPT INTO SELECTED SQUARES (Fig 7.16)

  40. STEPS 7 & 8: MODIFYING CONSIDERATIONS AND LIMITATIONS • SITE-SPECIFIC AND OPERATION-SPECIFIC CONDITIONS MAY AFFECT THE LAYOUT • EXAMPLES

  41. STEP 9: EVALUATION • AVAILABLE ALTERNATIVES MUST BE COMPARED • PICTORIAL DISPLAYS W/SUPERIMPOSED FLOWS • ADVANTAGES/DISADVANTAGES • COSTS • QUALITATIVE FACTOR RATINGS

  42. QUADRATIC ASSIGNMENT PROBLEM APPROACH

  43. OBJECTIVE OF QAP FIND THE MINIMUM COST ASSIGNMENT OF M DEPARTMENTS TO M LOCATIONS WHERE THE COST TO ASSIGN DEPARTMENT i TO LOCATION k AND DEPARTMENT j TO LOCATION l IS cijkl

  44. OBJECTIVE minijkl cijkl xik xjl withixik = 1 for all locations andkxik = 1 for all depts. NOTE: PROBLEM IS HARD TO SOLVE. IT’S BETTER TO USE HEURISTICS (See Eqns 7.13, 7.14)

  45. PAIRWISE EXCHANGE • MEASURE OF IMPORTANCE: TOTAL FLOW • START WITH A SOLUTION • PROCEED TO SWITCH PAIRS OF DEPARTMENTS THAT IMPROVE TOTAL FLOW UNTIL NO IMPROVING SWITCHES EXIST • Warning: No guarantees! (Fig. 7.17, Table 7.4)

  46. VNZ HEURISTIC • RANK DEPARTMENTS BY THEIR COST (INSTEAD OF THEIR CLOSENESS) • SELECT THE TWO MOST IMPORTANT DEPARTMENTS • CONSIDER SEQUENTIALLY ALL POSSIBLE EXCHANGES INVOLVING THE TWO DEPARTMENTS

  47. VNZ HEURISTIC • MAKE TWO PASSES THROUGH THE PAIRS OF DEPARTMENTS MAKING SWITCHES WHENEVER IMPROVEMENT IS ENCOUNTERED • See Example 7.4

  48. BRANCH AND BOUND • Francis & White method • Steps (see p. 230) • See Example 7.5 and Fig. 7.18

  49. GRAPH THEORETIC APPROACH • BOTH QUANTITATIVE AND QUALITATIVE DATA NEEDED • HOW ABOUT MAXIMIZING THE ADJACENCY SCORE? • PHYSICAL MAP OF DEPARTMENTS = PLANAR GRAPH G(N,A) • PLANAR GRAPHS HAVE DUALS • NODES>REGIONS - ARCS>BOUNDARIES • See Fig. 7.19

  50. GRAPH PROPERTIES 1.- THE DUAL OF A PLANAR GRAPH IS PLANAR 2.- THE MAXIMUM NUMBER OF ARCS IN A PLANAR GRAPH IS 3M-6 3.- A MAXIMALLY PLANAR GRAPH HAS 2M-4 FACES AND EACH FACE IS TRIANGULAR

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