Process Layout - Memorial University of Newfoundlandadfisher/7943-05/Chpt7/ch07_HO.pdf · Process Layout Chapter 7 To ... – Advantages ... Layout Types • Fixed-position layout
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•• DefDef’’nn–– Planning that involves decisions about physical Planning that involves decisions about physical
arrangement of economic activity centers needed by a arrangement of economic activity centers needed by a facilityfacility’’s various processes. s various processes.
–– An economic activity center can be anything that An economic activity center can be anything that consumes space.consumes space.
Process Layout PlanningProcess Layout Planning•• ChoicesChoices
–– What centers should we include?What centers should we include?•• Reflect process decisionsReflect process decisions•• Maximize productivityMaximize productivity
–– How much space and capacity for each center?How much space and capacity for each center?•• Inadequate space can reduce productivity and privacy and create Inadequate space can reduce productivity and privacy and create
hazards.hazards.•• Excess space is costly and can isolate employees. Often use spacExcess space is costly and can isolate employees. Often use space e
standards to guide designers.standards to guide designers.–– How to configure the space?How to configure the space?
•• The amount of space, its shape, and elements in itThe amount of space, its shape, and elements in it•• Atmosphere Atmosphere
–– Where should each be located?Where should each be located?•• Two aspects of location: relative and absolute.Two aspects of location: relative and absolute.
–– Relative location can affect travel time, material handling costRelative location can affect travel time, material handling cost, and , and communication.communication.
–– Absolute location can affect cost to change layout and customer Absolute location can affect cost to change layout and customer reactions.reactions.
–– Organizes resources around the process and groups work Organizes resources around the process and groups work stations or departments according to functionstations or departments according to function
–– Intermittent, low volume, highIntermittent, low volume, high--varietyvariety–– Flow strategy of King Flow strategy of King SoopersSoopers cake linecake line–– AdvantagesAdvantages
•• General purpose, flexible resources are less capital intensiveGeneral purpose, flexible resources are less capital intensive•• Less vulnerable to changes in product mix or new market Less vulnerable to changes in product mix or new market
strategiesstrategies•• Equipment utilization can be higher, because not dedicated to Equipment utilization can be higher, because not dedicated to
one product lineone product line•• Employee supervision can be more specializedEmployee supervision can be more specialized
–– Major challenge: locate centers so that they bring some Major challenge: locate centers so that they bring some order to the apparent chaos of divergent processes with order to the apparent chaos of divergent processes with jumbled work flowsjumbled work flows
–– A layout in which workstations or departments are arranged A layout in which workstations or departments are arranged in a linear pathin a linear path
–– Dedicates resources to a product or closely related product Dedicates resources to a product or closely related product familyfamily
–– Repetitive, highRepetitive, high--volume, continuous productionvolume, continuous production–– Less need to decouple one operation from the nextLess need to decouple one operation from the next–– Workstations or departments are arranged in a linear path, Workstations or departments are arranged in a linear path,
which is consistent with the routing sequence of the which is consistent with the routing sequence of the product, although a straight line is not always best, layouts product, although a straight line is not always best, layouts may take an L, O, S, or U shapemay take an L, O, S, or U shape
–– Challenge in designing product layoutsChallenge in designing product layouts•• Minimize resources used to achieve desired output rateMinimize resources used to achieve desired output rate•• Balance tasks, equalize the workload assigned to resources Balance tasks, equalize the workload assigned to resources
•• FixedFixed--position layoutposition layout–– Service or manufacturing site is fixed Service or manufacturing site is fixed
in place. Resources come to the in place. Resources come to the product, minimizing number of times product, minimizing number of times product must be moved.product must be moved.
–– Used for:Used for:•• Very large products as in building a new Very large products as in building a new
office complex, ships, roads, power office complex, ships, roads, power plants, airplanesplants, airplanes
•• Service of fragile or bulky itemService of fragile or bulky item
–– Using spatial language to show the competitive prioritiesUsing spatial language to show the competitive priorities–– Layout can influenceLayout can influence
•• Customer loyaltyCustomer loyalty•• Emotional connectEmotional connect•• Customer convenienceCustomer convenience•• Level of salesLevel of sales
•• Capital investmentCapital investment•• Materials handlingMaterials handling
–– Large flows should go short distancesLarge flows should go short distances–– Includes Includes stockpickingstockpicking in warehouse, customer convenience in store, and in warehouse, customer convenience in store, and
communication in officecommunication in office•• FlexibilityFlexibility
–– Facility remains desirable after significant changesFacility remains desirable after significant changes–– Can be easily and inexpensively adapted in response to themCan be easily and inexpensively adapted in response to them
•• Other criteriaOther criteria–– Labor productivityLabor productivity–– Equipment maintenanceEquipment maintenance–– Work environmentWork environment–– Organizational structureOrganizational structure
–– Is there enough volume to have a oneIs there enough volume to have a one--person line? person line? •• One worker operates several different machines simultaneously One worker operates several different machines simultaneously
to achieve line flow. to achieve line flow. •• The machines operate on their own for much of the cycle. The machines operate on their own for much of the cycle. •• The worker interacts with the machines as required, performing The worker interacts with the machines as required, performing
loading, unloading, or other operations that have not been loading, unloading, or other operations that have not been automated. automated.
–– Benefits are similar to those of flow lines: Benefits are similar to those of flow lines: •• lower WIP inventory, lower WIP inventory, •• reduced frequency of setup, reduced frequency of setup, •• labor savings through low cost automation, labor savings through low cost automation, •• simplified materials handling, simplified materials handling, •• reduced cycle time through overlapped operations.reduced cycle time through overlapped operations.
Designing Flexible Flow LayoutsDesigning Flexible Flow Layouts•• Gather Information Gather Information
–– Space requirements by center and available space and Space requirements by center and available space and closeness factors.closeness factors.
•• Tie space requirements to capacity and staffing plans.Tie space requirements to capacity and staffing plans.•• Calculate specific equipment and space needs for each centerCalculate specific equipment and space needs for each center•• Add Add ““circulationcirculation”” space such as aisles.space such as aisles.•• Consult with the managers and employees involvedConsult with the managers and employees involved
–– Closeness factorsCloseness factors•• Which items need to be close to each other, and which should Which items need to be close to each other, and which should
not be close to each other?not be close to each other?•• Closeness MatrixCloseness Matrix
–– A table that gives the relative importance of each pair of A table that gives the relative importance of each pair of centers being located close together.centers being located close together.
–– Closeness factors are indicators of the need for proximity Closeness factors are indicators of the need for proximity based on an analysis of information flows and the need for based on an analysis of information flows and the need for faceface--toto--face meetings.face meetings.
–– For the general case of n centers in a layout, there are nFor the general case of n centers in a layout, there are n--1 1 closeness factors found either in the row or column closeness factors found either in the row or column assigned to the center.assigned to the center.
–– At a manufacturing plant, the closeness factor could be the At a manufacturing plant, the closeness factor could be the number of trips between each pair of centers per day.number of trips between each pair of centers per day.
Designing Flexible Flow LayoutsDesigning Flexible Flow Layouts•• Gather Information (Continued)Gather Information (Continued)
–– Other considerationsOther considerations•• Absolute location criteriaAbsolute location criteria——departments fixed in place: relocation costs, departments fixed in place: relocation costs,
foundations, noise levels, and so forth.foundations, noise levels, and so forth.
•• Develop a block planDevelop a block plan
–– Most elementary way is trial and error, looking for patterns. CaMost elementary way is trial and error, looking for patterns. Can n supplement effort with computer help, such as the Process Layoutsupplement effort with computer help, such as the Process LayoutSolver from the OM5 software.Solver from the OM5 software.
–– Use a closeness matrix when evaluating a block plan and spottingUse a closeness matrix when evaluating a block plan and spottingpossible improvements in it.possible improvements in it.
Office of Budget Office of Budget ManagementManagement• Departments 1 and 6 close together• Departments 3 and 5 close together• Departments 2 and 3 close together
Designing Flexible Flow LayoutsDesigning Flexible Flow Layouts•• Consider Distance & Other MeasuresConsider Distance & Other Measures
–– Euclidean distance is the straightEuclidean distance is the straight--line, shortest distance between line, shortest distance between two points ... as the crow flies, so to speak. two points ... as the crow flies, so to speak.
–– Rectilinear distance assumes that the trip between two points isRectilinear distance assumes that the trip between two points ismade with a series of 90made with a series of 90°° turns. turns.
–– Calculating a weightedCalculating a weighted--distance scoredistance score•• Multiply each load (weight or trips per time period) between facMultiply each load (weight or trips per time period) between facilities ilities
times the distance (Euclidean or rectilinear) the load travels. times the distance (Euclidean or rectilinear) the load travels. The loadThe load--distance score is the sum of the products.distance score is the sum of the products.
•• Compare weightedCompare weighted--distance scores for alternative locations. Locations distance scores for alternative locations. Locations that generate big loads going short distances reduce ld. Of the that generate big loads going short distances reduce ld. Of the points points investigated, the location minimizing ld is the tentative best linvestigated, the location minimizing ld is the tentative best location.ocation.
–– Other factors, price of land, zoning, suitability of land for buOther factors, price of land, zoning, suitability of land for building, ilding, etc. may require consideration of other sites. etc. may require consideration of other sites.
Designing Flexible Flow LayoutsDesigning Flexible Flow Layouts•• Design a detailed layout Design a detailed layout
–– More exact sizes, shapes, and detail; show aisles, stairs, More exact sizes, shapes, and detail; show aisles, stairs, machines, desks, and the likemachines, desks, and the like
–– Other Decision Support ToolsOther Decision Support Tools•• Spreadsheet approach of OM ExplorerSpreadsheet approach of OM Explorer•• Automated Layout Automated Layout DEsignDEsign Program (ALDEP): sequence of Program (ALDEP): sequence of
entering departmentsentering departments–– First, randomly choose one.First, randomly choose one.–– Each successive department should have a strong closeness factorEach successive department should have a strong closeness factor
with one just entered. If no such relationship, choose randomly.with one just entered. If no such relationship, choose randomly.•• Computerized Relative Allocation of Facilities Technique Computerized Relative Allocation of Facilities Technique
(CRAFT)(CRAFT)–– Origins in space program and backboard wiring problemOrigins in space program and backboard wiring problem–– Successive pair exchangesSuccessive pair exchanges–– Improvement heuristics, some of most effective to this dayImprovement heuristics, some of most effective to this day
–– OutOut--andand--back selection patternback selection pattern•• Simplest situationSimplest situation•• One item picked at a time; go from dock to storage area and One item picked at a time; go from dock to storage area and
backback
–– Decision rule to minimize scoreDecision rule to minimize score•• Equal areas: Place departments with most trips closest to the Equal areas: Place departments with most trips closest to the
dock.dock.•• Unequal areas: Place departments with highest tripUnequal areas: Place departments with highest trip--toto--area ratio area ratio
closest to the dock.closest to the dock.
–– Various OptionsVarious Options•• Shifting demandShifting demand•• High density designs High density designs •• Different layout patternsDifferent layout patterns
–– OutOut--andand--back patternback pattern–– Route collection systemRoute collection system–– Batch picking systemBatch picking system–– Zone systemZone system
Designing Line Flow LayoutsDesigning Line Flow Layouts•• Common characteristicsCommon characteristics
–– Arranges work stations in sequenceArranges work stations in sequence–– Line flow from station to station, with each performing a set ofLine flow from station to station, with each performing a set of work work
elementselements–– Small or nonexistent inventory buffersSmall or nonexistent inventory buffers–– Production line or assembly lineProduction line or assembly line
•• Line BalancingLine Balancing–– Two basic questionsTwo basic questions
•• How many stations are needed?How many stations are needed?•• What work elements are assigned to each?What work elements are assigned to each?
•• AON networkAON network•• Cannot add a work element until all of its immediate predecessorCannot add a work element until all of its immediate predecessors are s are
shown. shown.
•• Desired output rateDesired output rate–– Matching demand to the production plan.Matching demand to the production plan.–– Job specialization and number of shifts worked: A typical Job specialization and number of shifts worked: A typical
automobile assembly plant is 60 cars per hour.automobile assembly plant is 60 cars per hour.
Designing Line Flow LayoutsDesigning Line Flow Layouts•• Cycle time / Cycle time / TaktTakt TimeTime
–– Inverse of desired output rate; convert to same time units as Inverse of desired output rate; convert to same time units as given for work elementsgiven for work elements
–– In general, In general, c = 1 / rc = 1 / r (r is desired production rate)(r is desired production rate)
•• Theoretical minimum number of stationsTheoretical minimum number of stations–– Productivity is maximized by minimizing the number of Productivity is maximized by minimizing the number of
stations.stations.–– The ultimate in balance is when the sum of workThe ultimate in balance is when the sum of work--element element
times at each station equals c.times at each station equals c.–– The theoretical minimum assumes perfect balance, which The theoretical minimum assumes perfect balance, which
may not be possible.may not be possible.–– In general, In general, TM = (sum of work element times) / c TM = (sum of work element times) / c
•• (always rounded up to nearest integer)(always rounded up to nearest integer)
Designing Line Flow LayoutsDesigning Line Flow Layouts•• Finding a solution Finding a solution
•• Step 1. Begin with station k = 1. Make a list of candidate workStep 1. Begin with station k = 1. Make a list of candidate workelements to assign to station k. Each candidate must satisfy elements to assign to station k. Each candidate must satisfy three conditions:three conditions:
–– It has not yet been assigned to this or any previous station.It has not yet been assigned to this or any previous station.–– All its predecessors have been assigned to this or a previous All its predecessors have been assigned to this or a previous
station.station.–– Its time cannot exceed the stationIts time cannot exceed the station’’s idle time, which accounts for all s idle time, which accounts for all
work elements already assigned. If none has been assigned, the work elements already assigned. If none has been assigned, the stationstation’’s idle time equals the cycle time.s idle time equals the cycle time.
•• If no such candidates can be found, go to step 4.If no such candidates can be found, go to step 4.
•• Step 2. Pick a candidate. Two decision rules are commonly Step 2. Pick a candidate. Two decision rules are commonly used for selecting from the candidate list.used for selecting from the candidate list.
–– Pick the candidate with the longest workPick the candidate with the longest work--element time. element time. •• Works in the most difficult ones first, saving the smaller ones Works in the most difficult ones first, saving the smaller ones for for
rounding out each station.rounding out each station.–– Pick the candidate having the largest number of followers. Pick the candidate having the largest number of followers.
•• Keeps options open for rest of solution.Keeps options open for rest of solution.–– Assign the candidate chosen to station k. If there are ties, breAssign the candidate chosen to station k. If there are ties, break ak
Designing Line Flow LayoutsDesigning Line Flow Layouts•• Finding a solutionFinding a solution (Continued)(Continued)
•• Step 3. Calculate the cumulative time of all tasks assigned so Step 3. Calculate the cumulative time of all tasks assigned so far to station k. Subtract this total from the cycle time to finfar to station k. Subtract this total from the cycle time to find the d the station's idle time. Go to step 1, and generate a new list of station's idle time. Go to step 1, and generate a new list of candidates.candidates.
•• Step 4. If some work elements are unassigned, but none are Step 4. If some work elements are unassigned, but none are candidates for station k, start a new station k + 1 and go to stcandidates for station k, start a new station k + 1 and go to step ep 1. Otherwise, you have a complete solution.1. Otherwise, you have a complete solution.
Designing Line Flow LayoutsDesigning Line Flow Layouts•• Other ConsiderationsOther Considerations
–– PacingPacing•• Allows material handling to be automatedAllows material handling to be automated•• Requires less storage areaRequires less storage area•• Is less flexible in handling unexpected delaysIs less flexible in handling unexpected delays
–– Behavioral factorsBehavioral factors•• Controversial aspect of lineControversial aspect of line--flow layoutsflow layouts•• Employees generally favor inventory buffers as a means of avoidiEmployees generally favor inventory buffers as a means of avoiding ng
mechanical pacingmechanical pacing
–– Number of models producedNumber of models produced•• MixedMixed--model linemodel line
–– Modify cycle timesModify cycle times•• May increase efficiencyMay increase efficiency•• Rebalancing frequencyRebalancing frequency