ME101, Final Examination, sample. Closed Book Examination (with the exception of one 3 x5 cards of handwritten notes, both sides, allowed)

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1 , sample Name Closed Book Examination (with the exception of one 3 x5 cards of handwritten notes, both sides, allowed) Only calculators allowed for calculations: Hewlett Packard: The HP 33s and HP 35s models, but no others. Texas Instruments: All TI-30X and TI-36X models. Casio: All fx-115 models. Time Limit: 2 hours, 50 minutes TOTAL READ THESE INSTRUCTIONS! Total Points Available: 100 The final page is a normal distribution Z-chart. Do not start until we tell you to. Write your SID at the top of every page after this one when you are told to begin.

2 1. Circle the correct response or responses and give a short justification for your answer: a. Average inventory level (increases)(decreases)(is unchanged) as order frequency increases. (Assume the sum total number of items ordered, over all orders in a year, is unchanged.) b. A (push)(pull) system schedules the release of work based on demand or demand forecasts, while a (push)(pull) system authorizes the release of work based on system status. c. A decrease in the interest rate (increases) (decreases) (has no effect on) the uniform annual cost of an investment. d. Reducing the number of inventory turns (increases) (decreases) (has no effect on) working capital. e. Control charts give an indication of (high and low tide in the ocean) (likelihood of producing defects) (when adjustments to the process are needed) (number of defective parts produced) (C p ) Circle all that apply. 2. Should a ceiling calculation (always rounding up) be used when calculating EOQ when 100% yield (no scrap) is expected? Why or why not?

3 3. Refering to the newspaper clipping excerpt below, explain how and why the changes GM has made to their factory in Lansing might increase efficiency and productivity. Smaller GM Takes Shape in Lansing By TIM MARTIN, Associated Press Writer Friday, December 8, PM Piles of crushed concrete and broken brick wait to be hauled away as bulldozers tear down old General Motors Corp. factories that have stood for a century on the banks of the Grand River in downtown Lansing. Behind the demolition, a gleaming white Cadillac factory built five years ago with state-of-the-art technology greets the next generation of auto workers. GM has a far smaller presence in the Lansing area than it had just a few years ago. But the automaker's new factories here are more efficient and better-suited to survive in the hyper-competitive automotive industry. GM ultimately was persuaded to build its Cadillac plant in the city. The automaker was impressed enough with the region's effort to open its crossover vehicle factory in nearby Delta Township a few years later. Both plants allow the automaker to produce a variety of vehicles on the same assembly line, cutting costs and increasing productivity. The Cadillac factory has been ranked the most productive luxury car plant in North America in 2003, 2004 and 2005, according to the annual Harbour Report on productivity. J.D. Power and Associates gave the factory its Gold Plant Award for The factory had the highest initial quality for all assembly operations in North and South America, and ranked third overall in the world. Cadillac officials credit the Lansing factory and the luxury CTS sedan for helping revive the nameplate. Cadillac sales through the first 11 months of this year are 28 percent higher than the same period in 2001, although they are nearly 4 percent lower than in Production employees work in teams of four to six members on the assembly line, each cross-trained to do every job in the group. Each worker has the power to stop the assembly line if a problem arises. That gives UAW members a mix of responsibility and authority not present in most GM factories. The factory model, and the community model in Lansing, could be one that GM borrows from as it reshapes itself worldwide. "This is exciting stuff," Cal Rapson, an international UAW vice president, said of what has happened in Lansing. "I think it's going to play a big role in the future."

4 4. Design specifications indicate that a part must be 150+/-3mm in length. a) A production line produces the parts with a mean length of mm and a standard deviation of 1 mm. The lengths appear to be normally distributed around the mean. What percentage of the parts produced are considered defective because they are not within the design specification? (See attached normal distribution tables). b) Describe the limitations of using this definition of defective (not within the prescribed error tolerance) with reference to the Taguchi quality loss function. c) Is C p or C pk the appropriate measure of production capability for this production line? Why? d) What is the value of C p or C pk (as appropriate) for this production line?

5 5. Stations k and k+1 process parts on a flow line. Each station consists of a single machine. Machine A, at station k, breaks down an average of every 30 hours (standard deviation is 2 hours), and requires 5 hours of repair time. Machine B, at station k+1, breaks down an average of every 50 hours (standard deviation is 3 hours), and requires 20 hours of repair time. Other stations consist of manual operations not subject to breakdowns. Processing time at each machine is 10 minutes. The transfer size is one part. a) Which of these two stations is the bottleneck and why? b) What size buffer (in other words, how many items should it hold) should be used between the two machines to guard against part shortages at station k+1? c) What size buffer (in other words, how many items should it hold) should be used after the machine at station k+1 to guard against part shortages at station k+2? d) Assume 1 hour of preventive maintenance to either machine ensures that it will continue operating without breaking down for at least 8 hours. If the same employees perform the preventive maintenance as perform the repairs, under what circumstances is this maintenance worth performing? e) Again, assume 1 hour of preventive maintenance to either machine ensures that it will continue operating without breaking down for at least 8 hours. If repairs are performed for free because the machines are under warranty, but the preventive maintenance must be done by your own employees, under what circumstances is this maintenance worth performing?

6 6. Using a 1% annual interest rate compounded annually, what is the uniform annual worth over the 4-year lifetime of a project with the estimated cash flows shown? (It is now start of year 0, all values are for start of year indicated.) Show your work. See interest rate tables at end of exam. Year Expenditures Income 0 $ $1500 $ $1500 $ $1500 $ $1500 $ Given the BOM for product X at right and its planned order release information indicated in the table below, using lot-for-lot scheduling for MRP, fill in the table for subassembly B to find its planned order releases. X period POR X 1 each B: lead time = 2 period GR SR I 4117 NR POR B C A 2 ea 1 ea 4 ea

7 8. A company is planning a new synchronous flow line. The anticipated demand for the product is 300,000 units per year, and the line will operate 50 weeks a year, 5 days a week, 2 shifts a day, 8 hours a shift. Repositioning time between stations is 8 seconds. The tasks timings and their dependencies are provided in the table below. a. What is the desired cycle time for the system? b. Determine the optimal way to divide the system into ordered stations (i.e. use the Ranked Positional Weight technique to balance the manufacturing line). i. Draw a precedence diagram. ii. Find the positional weight of each element. iii. Balance the line using RPW. c. What is the balance efficiency of the line as you have configured it? Task Task Time (seconds) Immediate Predecessors , , , ,11

8 9. A parts supplier makes gearbox assemblies. Each gearbox assembly uses three (3) shafts, and the shafts can be used only if they have a diameter less than 10.5 mm.; otherwise they are scrapped. The shafts that the shaft department produces have a mean diameter of 10.2 mm, with a standard deviation of 0.15 mm. The shafts are inspected only after they arrive at the assembly department. a. What fraction of the shafts the assembly department receives can be used to make the gearbox assemblies? b. If the company is using kanbans to control production, what is the optimal number of kanbans to use for transporting the shafts from the shaft department if the containers hold 60 shafts? The company always makes exactly 500 gearbox assemblies each week at a steady pace (working 5 days a week). The lead time for the shaft production is 1 day, with no variability.

9 10. For a goal that 97 1/2% of demand is fillable from safety stock (SS), if all of a chain s 10 retailers have the same demand mean and variance, what is the ratio between the total amount of SS that needs to be kept at retailers vs. the total amount of SS that needs to be kept at a centralized warehouse? 11. A certain manufacturer uses batch production. The setup and operation times in minutes are given as follows: Machine setup time per-part operation time Transfer time between machines for a batch of parts is 30 seconds. The overall defect rate q is 1%. Determine the following operating characteristics of the production process: a. The minimum manufacturing lead time (MLT) for producing a batch of 100 (non-defective) parts. b. The bottleneck machine, if there is one. c. The WIP for producing batches of 100 (non-defective) parts if only 2 batches are released into the system at any one time. d. The estimated production rate when producing batches of 100 (non-defective) parts if 8 batches are released into the system at any one time.

2.810 Manufacturing Processes and Systems. Quiz II (November 19, 2014) Open Book, Open Notes, Computers with Internet Off 90 Minutes

2.810 Manufacturing Processes and Systems Quiz II (November 19, 2014) Open Book, Open Notes, Computers with Internet Off 90 Minutes Write your name on every page. Clearly box your answers. State any assumptions