HW-03-19-08s_1 - IE 131 Homework Problems due 15 and 16...

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IE 131 Homework Problems due Mar 19, 2008 (Chs 13, 14, 15, and 16) 13.5 The continuous timing method is used to direct time study a manual task cycle consisting of four elements: a, b, c, and d. Two parts are produced each cycle. Element d is an irregular element performed once every six cycles. All elements were performance rated at 90%. The PFD allowance is 11%. Determine (a) the normalized time for the cycle and (b) the standard time per part. (c) If the worker completes 844 parts in an 8-hour shift during which she works 7 hours and 10 min, what is the worker’s efficiency? Element a b c d Observed time (min) 0.35 0.60 0.86 1.46 Solution : (a) T n = (0.86 + 0.60/6)(0.90) = 0.864 min per cycle (b) With two parts per cycle, the standard time per part is: T std = 0.864(1 + 0.11)/2 = 0.4795 = 0.48 min (c) H std = 844(0.48)/60 = 6.752 hr E w = 6.752/8.0 = 0.844 = 84.4% 13.7 The time and performance rating values in the table below were obtained using the snapback timing method on the work elements in a certain manual repetitive task. All elements are worker-controlled. All elements were performance rated at 85%. Element e is an irregular element performed every five cycles. A 15% PFD allowance is applied to the cycle. Determine (a) the normal time and (b) the standard time for this cycle. If the worker’s performance during actual production is 125% on all manual elements for seven actual hours worked on an eight-hour shift, (c) how many units will be produced and (d) what is the worker’s efficiency? Work element a b c d e Observed time (min) 0.61 0.42 0.76 0.55 1.10 Solution : (a) T n = (0.61 + 0.42 + 0.76 + 0.55 + 1.10/5)(0.85) = 2.176 min (b) T std = 2.176(1 + 0.15) = 2.502 min (c) Worker performance P w = 125% for 7.0 hr actually worked in an 8-hour shift T c = T n / P w = 2.176/1.25 = 1.741 min Q = 7(60)/1.741 = 241.2 rounded down to 241 pc (d) H std = 241(2.502)/60 = 10.05 hr, and E w = 10.05/8.0 = 1.256 = 125.6% 13.9 The continuous timing method in direct time study was used to obtain the element times for a worker-machine task as indicated in the table below. Element c is a machine-controlled element and the time is constant. Elements a, b, d, e, and f are operator-controlled and external to the ma- chine cycle, and were performance rated at 80%. If the machine allowance is 25%, and the worker allowance for personal time, fatigue, and delays is 15%, determine (a) the normal time and (b) standard time for the cycle. (c) If the worker completed 360 work units working 7.2 hours on an 8-
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