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HW-01-30-08s

# HW-01-30-08s - IE 131 Solutions for Problems due Jan 30(Chs...

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IE 131 Solutions for Problems due Jan 30 (Chs 2 and 3) 2.11 The normal time for a work cycle in a worker-machine system is 6.27 min. For setting the standard time, the PFD allowance factor is 12%, and the machine allowance factor is 25%. The work cycle includes manual elements totaling a normal time of 5.92 min, all but 0.65 min of which are performed as internal elements. Determine (a) the standard time for the cycle and (b) the daily output at standard performance. (c) During an 8-hour shift, the worker lost 39 min due to personal time, rest breaks, and delays, and she produced 72 pieces. What was the worker’s pace on the operator-controlled portion of the shift? Solution : (a) Machine time per cycle T m = 6.27 – 0.65 = 5.62 min Internal normal time T nwi = 5.92 – 0.65 = 5.27 min T std = 0.65(1.12) + Max{5.27(1.12), 5.62(1.25)} = 0.728 + 7.025 = 7.753 min (b) Q std = 8(60)/7.753 = 61.9 pc (if rounded, 62 pc) (c) Time worked = 480 – 39 = 441 min Given that Q = 72 pc, then total machine time = 72(5.62) = 404.64 min Total worker-controlled time = 441 – 404.64 = 36.36 min Given T nw = 0.65 min, total worker-controlled time at normal pace = 72(0.65) = 46.8 min P w = 46.8/36.36 = 1.287 = 128.7% 2.15 A new stamping plant must supply an automotive final assembly plant with stampings, and the number of new stamping presses must be determined. Each press will be operated by one worker. The plant will operate one 8-hour shift per day, five days per week, 50 weeks per year. The plant must produce a total of 20,000,000 stampings annually. However, 400 different stamping designs are required, in batch sizes of 5000 each, so each batch will be produced 10 times per year to minimize build-up of inventory. Each stamping takes 6 sec on average to produce. Scrap rate averages 2% in this type of production. Before each batch, the press must be set up, with a standard time per setup of 3.0 hours. Presses are 95% reliable (availability = 95%) during production and 100% reliable during setup. Worker efficiency is expected to be 100%. How many new stamping presses and operators will be required? Solution : Number of setups = 20,000,000/5,000 = 4,000 setups/yr Setup workload WL su = 4,000(3.0) = 12,000 hr/yr Cycle time T c = 6 sec = 0.1 min Production workload WL p = 20,000,000(0.1)/0.98(60) = 34,013.6 hr/yr Available time for setup AT su = 2,000(1.0) = 2,000 hr/yr per press Available time for production AT p = 2000(0.95) = 1900 hr/yr n = w = 34,013.6/1,900 + 12,000/2,000 = 17.9 + 6 = 23.9 rounded up to 24 presses and 24 operators 2.16 Solve the previous problem, except the plant will operate two 8-hour shifts instead of one.

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HW-01-30-08s - IE 131 Solutions for Problems due Jan 30(Chs...

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