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

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    SOLUTIONS MANUAL FOR by Lean Production for Competitive Advantage: A Comprehensive Guide to Lean Methodologies and Management Practices John Nicholas

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    TABLE OF CONTENTS Preface Suggestions for Using Book Course Emphasis Case Studies and Videos Classroom Simulations Cellular Manufacturing Pull Production End-of-Chapter Questions and Problems: Level of Difficulty and Suggestions Chapter 1. Race without a Finish Line Answers to Questions Chapter 2. Fundamentals of Continuous Improvement Answers to Questions Solutions to Problems Chapter 3. Value Added and Waste Elimination Answers to Questions Solutions to Problems Chapter 4. Customer Focused Quality Answers to Questions Chapter 5. Small Lot Production Answers to Questions Solutions to Problems Chapter 6. Setup-Time Reduction Answers to Questions Solutions to Problems Chapter 7. Maintaining and Improving Equipment Answers to Questions Solutions to Problems Chapter 8. Pull Production Systems Answers to Questions Solutions to Problems Chapter 9. Focused Factories and Group Technology Answers to Questions Solutions to Problems

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    Chapter 10. Workcells and Cellular Manufacturing Answers to Questions Solutions to Problems Chapter 11. Standard Operations Answers to Questions Solutions to Problems Chapter 12. Quality at the Source and Mistake-Proofing Answers to Questions Solutions to Problems Chapter 13. Uniform Flow and Mixed-Model Scheduling Answers to Questions Solutions to Problems Chapter 14. Synchronizing and Balancing the Process Answers to Questions Solutions to Problems Chapter 15. Planning and Control in Pull Production Answers to Questions Solutions to Problems Chapter 16 Lean Production in the Supply Chain Answers to Questions Solutions to Problems

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    CLASSROOM SIMULATIONS Cellular Manufacturing Simulation This 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 on an automatic machine, 3) two operators, each in a subcell; and 4) two operators, each in a subcell and where one must wait on an automatic machine. Materials Required • Child’s building materials such as Legos, K’nex, etc. This simulation explained below uses Legos. • 18 plastic or Styrofoam drinking cups • Cards to mark the location of the “in” box, the “out” box, two holding areas, and six workstations 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 finished products from the “out” box, delivering them to the supplier, and returning to the cell with full cups of parts. • One student will be the “timer.” This student must have watch or other time-keeping device showing seconds. • One student will pretend to be an automatic machine (this student also must have a time-keeping device showing seconds). The cell is arranged into a U-shape with six workstations and an “in” box at one end and an “out” box at the other. Located at each workstation are two cups, each with the exact number and kind of parts to be added to the product at the station. Also at each station is a “model” to remind the student where the parts should be added to the product and what the product will look like upon completing tasks at the station. Figure 1 shows the arrangement of stations. In the simulation the workstations can be located on two tables, with the operators walking in between.

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    Figure 1 Figures 2 and 3 show photos of the parts to be added and the product’s appearance after adding parts at the stations. (This is only a suggestion.) Note, Figures 2 and 3 include holding 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 who serve 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 parts for all the simulations. At the supplier location are six empty cups and six cups containing the appropriate numbers and kinds of parts. The latter cups are not to be used ; they are to serve as guides, showing the exact number and kinds of parts that should go into the other six cups that will be delivered to the cell. Full cups delivered to the cell are replaced with empty 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 the cell 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 six workstations. Figure 2 Figure 3

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    Workcell Simulation A. Computing Cycle Time with One Worker One 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, and puts the completed product in the out box. He then goes to the in box, takes another product 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 timer determines the time when the simulation should begin, says “go,” then notes the time whenever the operator puts a completed product in the outbox. The simulation should run long enough for the operator to complete at least four finished products. The cycle time of the cell is the time between when finished products are put in the out box. Ignore the time for the first product and compute the average of the time for the remaining products. Following is recommendation for the number of parts to be added at each station: Station 1 2 parts Station 2 2 parts Station 3 4 parts Station 4 4 parts Station 5 4 parts Station 6 2 parts Workcell Simulation B. Computing Cycle Time with One Worker and an Automatic Machine This simulation is identical to the first but shows what happens when an automatic machine is inserted in the process, and when the cycle time of the machine exceeds the operator’s total walk time and task time. A student pretending to be the machine sits at station 3. The operator does everything he did in the first simulation, except upon completing the assembly task at station 3 he hands the product to the “machine,” then takes the product the machine previously held and continues with the assembly tasks at the other stations. (Note, in the first go-round, the machine will not be holding a product for the operator to take; for this one instance , the operator should make two products, one to 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 the machine 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 have elapsed. (The time does not have to be 90 seconds; it must, however, be somewhat longer than the cycle time computed in the first simulation, above. The purpose of Simulation 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 the operator arrives at the machine, the operator will have to wait until the machine is finished before he can take the product from the machine, give the machine another product, 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 the supplier, 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 four finished products. The cycle time of the cell is the time between when finished products are put in the out box. Ignore the time for the first product and compute the average of the time for the remaining products. Workcell Simulation C. Computing Cycle Time with Two Subcells The six workstations are divided between two subcells with two holding areas between them as shown in Figure 1c and 1d, and Figures 2 and 3. Two students serve as operators, one for each subcell. Shown in Figure 1c and 1d, operator 2 picks up a product at the in box, adds parts at stations 1 and 2, then puts the product into holding area a. He then goes to holding area b, takes the product from there, adds parts at station 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 at stations 3-5, then puts the product in holding area b. If ever an operator arrives at a holding 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 four finished products. The cycle time of the cell is the time between when finished products are put in the out box. Ignore the time for the first product and compute the average time for the remaining products. Note: the assembly tasks in the workcells should be “rigged” so that operator 1 will take much longer than operator 2. In the recommendation above, operator 2 adds a total of 6 parts to the products, operator 1 adds a total of 12. As a result, every time operator 2 arrives at holding area he will have to wait for operator 1. Thus, the times when a finished product are put in the out box and, hence, the cell cycle time are determined by operator 1. Workcell Simulation D. Computing Cycle Time with Subcells and an Automatic Machine In this simulation everything is the same as in Simulation C except that located at station 3 is an automatic machine, which performs the same way as in simulation B. Thus, a student 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 it up 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 determined by the machine, which takes longer than the task and walk time of either operator 1 or 2. Discussion All 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 reconfigured to modify the cycle time.

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    Pull Production Simulation This simulation demonstrates the pull production process and the ability of the process to respond to demand depending on buffer size and process cycle time. Materials Required • Child’s building materials such as Legos, K’nex, etc. This simulation explained below 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 finished products from the “out” box, delivering them to the supplier, and returning to the cell with 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 each pair of workstations and at the end of the line is a buffer. Located at each workstation are two cups, each with the exact number and kind of parts to be added to the product at that station. Also at the station is a “model” to remind the student where the parts should be added to the product and what the product will look like upon completing tasks at the station. Figure 4 shows the arrangement of stations and locations of WIP and finished goods (FG) buffers. Figures 5 and 6 show the actual K’nex pieces and WIP items (“To Customer” 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 the workcell simulations, products taken from the FG (finished goods or To Customer) buffer are handed to these students, who tear them down into pieces and put the pieces into the parts cups. The process of tearing products is necessary to “recycle” parts and ensure enough parts for all the simulations. At the supplier location are four empty cups and four cups containing the appropriate numbers and kinds of parts. The latter cups are not to be used ; they are to serve as guides, showing the exact number and kinds of parts that should go into the six cups that will be delivered to the cell. A “material handler” who doubles as the “customer” takes completed products from the FG buffer, gives them to the supplier, and returns to the line with full parts cups. Throughout each simulation the role of the handler is to replenish parts in the parts cups at the line’s four workstations. In the suggested simulation, the buffer size is two; thus, in between each pair of workstations are two units of WIP (partially completed products), at the FG buffer are two 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 to replenish the buffer or cup. This is represented in Figure 7. Figure 7. Pull Simulation A: Demonstrating the Pull Production Process The simulation begins by the customer/material handler taking one of the finished products from the FG buffer. The FG buffer then has only one unit, which signals workstation 4 to replenish it. The operator at workstation 4 takes one unit from the WIP buffer to his right (assume operators are facing toward the suppliers in Figure 7) and parts 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 3 takes one unit from the buffer to his right and parts from one of the part cups to replenish the buffer to his left. The process is the same for workstations 2 and 1. Every workstation replenishes the missing unit from the WIP buffer. Whenever the number of full parts cups (RM buffer) drops to one, that signals the material handler to replenish it with a full cup from the supplier. (As described, the students who serve as the suppliers are filling cups with parts from torn down products delivered by the material handler.) Pull Simulation B: Demonstrating Limitations of Pull Production Imposed by Buffer Size The purpose of this simulation is to show that demand in the pull production process must be somewhat uniform, and that the ability of the system to respond to small demand variations is limited by the buffer size. This simulation begins by the material handler taking two of the finished products from the FG buffer. Since the FG buffer is then zero, that signals workstation 4 to replenish two units. The operator at workstation 4 takes two unit from the WIP buffer to his right (again, assume operators are facing toward the suppliers in Figure 5) and parts from both parts 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 unit from the buffer to his right and parts from both parts cups to replenish the buffer to his left. The process is the same for workstations 2 and 1. Every workstation replenishes the two missing units from the buffer. Meantime, the material handler is busy replenishing two parts cups at every workstation and 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 the increased demand of two units. For another simulation, suppose demand increases to three units. As the simulation demonstrates, the whole system then gets bogged down. Only two units are available at FG, which means the customer has to wait for the third. As soon as the additional unit arrives at FG, it is immediately taken by the customer. Since the FG buffer is now down to zero again, that signals workstation 4 to replenish it with two more units. The same thing occurs upstream at all the workstations and at the suppliers. The entire process takes awhile to get caught up. Pull Simulation C: Pull Production and Cycle Time For this simulation select a student to time the process. The student must have a watch or other time-keeping device showing seconds. Before starting the simulation, measure the length of time it takes for each operator to perform the assembly tasks. Suppose the time

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    of the slowest operator is 30 seconds. This says that the cycle time of the process is 30 seconds/unit and that the average demand rate for the process should not exceed two units per minutes (30 seconds per unit). The simulation starts when the timer says “go.” At this time the customer/ material handler withdraws a product from the FG buffer. About 28 seconds later the timer tells the material handler to withdraw another unit from the FG buffer. About 35 seconds later the timer tell the customer to withdrawn another unit. The same happens after another 29, 34, 32, 29, etc. seconds. The simulation should show that long as the withdrawal interval, the takt time (30 sec/unit), for the average demand does not exceed the cycle time of the process, the process can easily meet demand. The simulation is now repeated, beginning when the timer says “go.” But this time the timer 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 is less than the cycle time. As the simulation will show, the process falls behind and is never able to catch up with demand. Pull Simulation D: Pull Production with Process Steps Located Far Apart As another variation, workstation 1 through 4 can be located in various positions throughout the room. The purpose of this simulation is to show that the pull production process 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 between station and at stations might have to be increased and/or the cycle time of the process must be decrease, depending on the demand rate.. Discussion All 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 in takt time.

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    End-of-Chapter Questions and Problems: Level of Difficulty Most end-of-chapter questions and problems can be easily answered by reading the chapter and working through the example problems. Some of the questions and problems, however, are more challenging and require conceptualization, literature research, personal experience, or consideration of specific applications not discussed in the book. These questions and problems are denoted in the answers below with an asterisk (*). Instructors should consider using some of these more-difficult questions and problems as part of the 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 upon topics covered in the book, and some can be used to suggest topics and analysis methods not covered in the book.

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