Solution Manual For Lean Production for Competitive Advantage, 1th Edition

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SOLUTIONS MANUAL FORbyLean Production forCompetitive Advantage:A Comprehensive Guide toLean Methodologies andManagement PracticesJohn Nicholas

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TABLE OF CONTENTSPrefaceSuggestions for Using BookCourse EmphasisCase Studies and VideosClassroom SimulationsCellular ManufacturingPull ProductionEnd-of-Chapter Questions and Problems:Level of Difficulty and SuggestionsChapter 1.Race without a Finish LineAnswers to QuestionsChapter 2.Fundamentals of Continuous ImprovementAnswers to QuestionsSolutions to ProblemsChapter 3.Value Added and Waste EliminationAnswers to QuestionsSolutions to ProblemsChapter 4.Customer Focused QualityAnswers to QuestionsChapter 5.Small Lot ProductionAnswers to QuestionsSolutions to ProblemsChapter 6.Setup-Time ReductionAnswers to QuestionsSolutions to ProblemsChapter 7.Maintaining and Improving EquipmentAnswers to QuestionsSolutions to ProblemsChapter 8.Pull Production SystemsAnswers to QuestionsSolutions to ProblemsChapter 9.Focused Factories and Group TechnologyAnswers to QuestionsSolutions to Problems

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Chapter 10.Workcells and Cellular ManufacturingAnswers to QuestionsSolutions to ProblemsChapter 11.Standard OperationsAnswers to QuestionsSolutions to ProblemsChapter 12.Quality at the Source and Mistake-ProofingAnswers to QuestionsSolutions to ProblemsChapter 13.Uniform Flow and Mixed-Model SchedulingAnswers to QuestionsSolutions to ProblemsChapter 14.Synchronizing and Balancing the ProcessAnswers to QuestionsSolutions to ProblemsChapter 15.Planning and Control in Pull ProductionAnswers to QuestionsSolutions to ProblemsChapter 16Lean Production in the Supply ChainAnswers to QuestionsSolutions to Problems

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CLASSROOM SIMULATIONSCellular Manufacturing SimulationThis simulation demonstrates how cycle time is computed under different circumstances:1) one operator in an assembly cell, 2) one operator in an assembly cell who must wait onan automatic machine, 3) two operators, each in a subcell; and 4) two operators, each in asubcell and where one must wait on an automatic machine.Materials Required•Child’s building materials such as Legos, K’nex, etc. This simulation explainedbelow uses Legos.•18 plastic or Styrofoam drinking cups•Cards to mark the location of the “in” box, the “out” box, two holding areas, and sixworkstations and number of pieces to be added to the product at each station.•Two time-keeping devices (watch, clock, cell phone, etc.) that show seconds.Six or Seven Students Participate in the Simulation•Two students will be cell operators and assemble the product•One or two students will serve as suppliers to tear down products and fill parts cups(explained below)•One student will double as both the customer and material handler, taking finishedproducts from the “out” box, delivering them to the supplier, and returning to the cellwith full cups of parts.•One student will be the “timer.” This student must have watch or other time-keepingdevice showing seconds.•One student will pretend to be an automatic machine (this student also must have atime-keeping device showing seconds).The cell is arranged into a U-shape with six workstations and an “in” box at one end andan “out” box at the other. Located at each workstation are two cups, each with the exactnumber and kind of parts to be added to the product at the station. Also at each station isa “model” to remind the student where the parts should be added to the product and whatthe product will look like upon completing tasks at the station. Figure 1 shows thearrangement of stations.In the simulation the workstations can be located on two tables,with the operators walking in between.

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Figure 1Figures 2 and 3 show photos of the parts to be added and the product’s appearance afteradding parts at the stations. (This is only a suggestion.)Note, Figures 2 and 3 includeholding areas, which are not needed for Simulation A and B.Located nearby the cell (not shown in Figures 1-3) should be one or two students whoserve as the parts suppliers.Products that are taken from the out box are handed to them;the students tear the products down into pieces, and put the pieces into the parts cups.This process of tearing products is necessary to “recycle” parts and ensure enough partsfor all the simulations.At the supplier location are six empty cups and six cups containing the appropriatenumbers and kinds of parts. The latter cupsare not to be used; they are to serve asguides, showing the exact number and kinds of parts that should go into the other sixcups that will be delivered to the cell. Full cups delivered to the cell are replaced withempty cups coming from the cell. The “material handler” who doubles as the “customer”takes completed products from the out box, gives them to the suppliers, and returns to thecell with full parts cups. Throughout each simulation the role of the handler is to take

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products from the out box and to replenish parts to the in box and the cell’s sixworkstations.Figure 2Figure 3

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Workcell Simulation A. Computing Cycle Time with One WorkerOne student serves as the cell operator and walks around the cell and builds the product.The student takes a product from the in box, adds pieces at each of the six stations, andputs the completed product in the out box. He then goes to the in box, takes anotherproduct and repeats the cycle. As described above, another student (the customer/material handler) takes the completed product from the out box, gives it to the supplier,and delivers full cups of parts from the supplier to the appropriate stations in the cell.Another student, the “timer,” sits near the out box and keeps track of time. The timerdetermines the time when the simulation should begin, says “go,” then notes the timewhenever the operator puts a completed product in the outbox. The simulation shouldrun long enough for the operator to complete at least four finished products. The cycletime of the cell is the time between when finished products are put in the out box. Ignorethe time for the first product and compute the average of the time for the remainingproducts.Following is recommendation for the number of parts to be added at each station:Station 12 partsStation 22 partsStation 34 partsStation 44 partsStation 54 partsStation 62 partsWorkcell Simulation B. Computing Cycle Time with One Worker and anAutomatic MachineThis simulation is identical to the first but shows what happens when an automaticmachine is inserted in the process, and when the cycle time of the machine exceeds theoperator’s total walk time and task time.A student pretending to be the machine sits atstation 3.The operator does everything he did in the first simulation, except uponcompleting the assembly task at station 3 he hands the product to the “machine,” thentakes the product the machine previously held and continues with the assembly tasks atthe other stations. (Note, in the first go-round, the machine will not be holding a productfor the operator to take;for this one instance, the operator should make two products, oneto take to the next station, the other to give to the machine.)Upon being handed the product, the “machine” is “turned on.” The student playing themachine notes the time on his watch. Assume the machine must run for 90 seconds.This means the machine will not “give up” the product it is holding until 90 seconds haveelapsed. (The time does not have to be 90 seconds; it must, however, be somewhatlongerthan the cycle time computed in the first simulation, above. The purpose ofSimulation B is to show that if the machine cycle time is long enough, it, not the operator

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cycle time from Simulation A, determines the cell cycle time.). The next time theoperator arrives at the machine, the operator will have to wait until the machine isfinished before he can take the product from the machine, give the machine anotherproduct, and move on the next station.As before, the timer keeps track of each time a completed product is put in the out box.As before, the customer/handler takes products from the out box, gives them to thesupplier, and returns with parts for the cell’s in box and six assembly stations.Again, the simulation should run long enough for the operator to complete at least fourfinished products. The cycle time of the cell is the time between when finished productsare put in the out box. Ignore the time for the first product and compute the average ofthe time for the remaining products.Workcell Simulation C. Computing Cycle Time with Two SubcellsThe six workstations are divided between two subcells with two holding areas betweenthem as shown in Figure 1c and 1d, and Figures 2 and 3.Two students serve asoperators, one for each subcell.Shown in Figure 1c and 1d, operator 2 picks up aproduct at the in box, adds parts at stations 1 and 2, then puts the product into holdingarea a.He then goes to holding area b, takes the product from there, adds parts atstation 6, puts the finished product in the out box, and goes to the inbox and repeats.When operator 1 arrives at holding area a, he takes a product from there, adds pieces atstations 3-5, then puts the product in holding area b. If ever an operator arrives at aholding area that is empty, he must wait until the other operator deposits a product there.The students acting as timer, customer/material handler, and supplier perform as before.Again, the simulation should run long enough for the operator to complete at least fourfinished products. The cycle time of the cell is the time between when finished productsare put in the out box. Ignore the time for the first product and compute the average timefor the remaining products.Note: the assembly tasks in the workcells should be “rigged” so that operator 1 will takemuch longer than operator 2.In the recommendation above, operator 2 adds a total of 6parts to the products, operator 1 adds a total of 12.As a result, every time operator 2arrives at holding area he will have to wait for operator 1.Thus, the times when afinished product are put in the out box and, hence, the cell cycle time are determined byoperator 1.Workcell Simulation D. Computing Cycle Time with Subcells and an AutomaticMachineIn this simulation everything is the same as in Simulation C except that located at station3 is an automatic machine, which performs the same way as in simulation B. Thus, astudent pretending to be the machine should sit at that station and, as in Simulation B,every time the operator hands him a product, must hold it for 90 seconds before giving itup the next time the operator comes around. Since the machine time takes longer than

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the cycle time as computed in simulation C the cycle time of the cell will be determinedby the machine, which takes longer than the task and walk time of either operator 1 or 2.DiscussionAll the simulations should be followed with discussions about the results, lessons learned,and how the workstations, tasks, or number of workers might be altered or reconfiguredto modify the cycle time.

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Pull Production SimulationThis simulation demonstrates the pull production process and the ability of the process torespond to demand depending on buffer size and process cycle time.Materials Required•Child’s building materials such as Legos, K’nex, etc. This simulation explainedbelow uses K’nex.•20 plastic or Styrofoam drinking cups•Timing device (clock, watch, etc)Six or Seven Students Participate in the Simulation•Four students will be line operators and assemble the product•One or two students will serve as suppliers to tear down products and fill parts cups(explained below)•One student will double as the customer and material handler, taking finishedproducts from the “out” box, delivering them to the supplier, and returning to the cellwith full cups of parts.•One student to serve as timer in Pull Simulation C.The process consists of four stages (workstations) arranged in a line.In between eachpair of workstations and at the end of the line is a buffer.Located at each workstationare two cups, each with the exact number and kind of parts to be added to the product atthat station. Also at the station is a “model” to remind the student where the parts shouldbe added to the product and what the product will look like upon completing tasks at thestation. Figure 4 shows the arrangement of stations and locations of WIP and finishedgoods (FG) buffers.Figures 5 and 6 show the actual K’nex pieces and WIP items (“ToCustomer” is the finished goods buffer).Figure 4

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Figure 5.Figure 6

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Located near the line are one or two students who serve as the parts supplier.As in theworkcell simulations, products taken from the FG (finished goods or To Customer) bufferare handed to these students, who tear them down into pieces and put the pieces into theparts cups.The process of tearing products is necessary to “recycle” parts and ensureenough parts for all the simulations.At the supplier location are four empty cups and four cups containing the appropriatenumbers and kinds of parts. The latter cupsare not to be used; they are to serve asguides, showing the exact number and kinds of parts that should go into the six cups thatwill be delivered to the cell. A “material handler” who doubles as the “customer” takescompleted products from the FG buffer, gives them to the supplier, and returns to the linewith full parts cups. Throughout each simulation the role of the handler is to replenishparts in the parts cups at the line’s four workstations.In the suggested simulation, thebuffer sizeis two; thus, in between each pair ofworkstations are two units of WIP (partially completed products), at the FG buffer aretwo fully-completed products, and at every workstation are two cups of parts.Whenever the buffer anywhere drops to one unit or one cup, that signals the need toreplenish the buffer or cup. This is represented in Figure 7.Figure 7.Pull Simulation A: Demonstrating the Pull Production ProcessThe simulation begins by the customer/material handler taking one of the finishedproducts from the FG buffer. The FG buffer then has only one unit, which signalsworkstation 4 to replenish it. The operator at workstation 4 takes one unit from the WIPbuffer to his right (assume operators are facingtowardthe suppliers in Figure 7) andparts from one of the part cups to replenish the FG buffer. Since the WIP buffer then has

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only one unit, that signals workstation 3 to replenish it. The operator at workstation 3takes one unit from the buffer to his right and parts from one of the part cups to replenishthe buffer to his left. The process is the same for workstations 2 and 1.Everyworkstation replenishes the missing unit from the WIP buffer.Whenever the number of full parts cups (RM buffer) drops to one, that signals thematerial handler to replenish it with a full cup from the supplier.(As described, thestudents who serve as the suppliers are filling cups with parts from torn down productsdelivered by the material handler.)Pull Simulation B: Demonstrating Limitations of Pull Production Imposed byBuffer SizeThe purpose of this simulation is to show that demand in the pull production processmust be somewhat uniform, and that the ability of the system to respond to small demandvariations is limited by the buffer size.This simulation begins by the material handler takingtwoof the finished products fromthe FG buffer. Since the FG buffer is then zero, that signals workstation 4 to replenishtwounits. The operator at workstation 4 takes two unit from the WIP buffer to his right(again, assume operators are facingtowardthe suppliers in Figure 5) and parts from bothparts cups to replenish the FG buffer. The WIP buffer on the right then has zero units,which signals workstation 3 to replenish it. The operator at workstation 3 takes two unitfrom the buffer to his right and parts from both parts cups to replenish the buffer to hisleft. The process is the same for workstations 2 and 1.Every workstation replenishesthe two missing units from the buffer.Meantime, the material handler is busy replenishing two parts cups at every workstationand the suppliers are busy filling the cups.Because the entire system has two units of buffer, it is able in short time to respond to theincreased demand of two units.For another simulation, suppose demand increases tothreeunits. As the simulationdemonstrates, the whole system then gets bogged down. Only two units are available atFG, which means the customer has to wait for the third. As soon as the additional unitarrives at FG, it is immediately taken by the customer. Since the FG buffer is now downto zero again, that signals workstation 4 to replenish it with two more units.The samething occurs upstream at all the workstations and at the suppliers. The entire processtakes awhile to get caught up.Pull Simulation C: Pull Production and Cycle TimeFor this simulation select a student to time the process. The student must have a watch orother time-keeping device showing seconds.Before starting the simulation, measure thelength of time it takes for each operator to perform the assembly tasks. Suppose the time

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of theslowestoperator is 30 seconds.This says that the cycle time of the process is 30seconds/unit and that the average demand rate for the process should not exceed two unitsper minutes (30 seconds per unit).The simulation starts when the timer says “go.”At this time the customer/ materialhandler withdraws a product from the FG buffer. About 28 seconds later the timer tellsthe material handler to withdraw another unit from the FG buffer. About 35 seconds laterthe timer tell the customer to withdrawn another unit.The same happens after another29, 34, 32, 29, etc. seconds. The simulation should show that long as the withdrawalinterval, the takt time (30 sec/unit), for the average demand does not exceed the cycletime of the process, the process can easily meet demand.The simulation is now repeated, beginning when the timer says “go.” But this time thetimer instructs the material handler to withdraw a unit from FG buffer after 20, 22, 24,19, etc. seconds to illustrate what happens when the takt time isless thanthe cycle time.As the simulation will show, the process falls behind and is never able to catch up withdemand.Pull Simulation D: Pull Production with Process Steps Located Far ApartAs another variation, workstation 1 through 4 can be located in various positionsthroughout the room. The purpose of this simulation is to show that the pull productionprocess also works when stations of the process are not located near each other. Note,however, that if the stations are located far enough away, then the buffer sizes betweenstation and at stations might have to be increased and/or the cycle time of the processmust be decrease, depending on the demand rate..DiscussionAll the simulations should be followed with discussions about the results, lessons learned,and how the process tasks, buffers, etc., might be modified to accommodate changes intakt time.

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End-of-Chapter Questions and Problems: Level of DifficultyMost end-of-chapter questions and problems can be easily answered by reading the chapter andworking through the example problems.Some of the questions and problems, however, aremore challenging and require conceptualization, literature research, personal experience, orconsideration of specific applications not discussed in the book.These questions and problemsare denoted in the answers below with an asterisk (*).Instructors should consider using some of these more-difficult questions and problems as part ofthe lecture material.The answers provided will allow the instructor to discuss problems,concepts, issues, and applications that go beyond the book.Some of these more-difficult questions and problems can be used to illustrate and expand upontopics covered in the book, and some can be used to suggest topics and analysis methods notcovered in the book.

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