Exam I - Review Questions- KEY2

# Several identical machines are available if each

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……………………………………………………………………………………………………… Several identical machines are available. If each machine is used for 7.0 hours per shift, two shifts per day, and 20 days per month, how many machines will be needed to meet the aggregate requirement? (Assume negligible setup time). Total time needed = 3280 * 1 = 3280 hours / month No. of machines = 3280 / ( 2 * 7 * 20) = 11.71 Round up We need 12 machines. Product Time Hrs / unit Demand Demand in standard units A 2.0 80 (2/1 *80 ) 2 * 80 / 1 = 160 B 3.0 200 (3/1 *200 ) 3 * 200 / 1 = 600 C 1.5 480 (1.5/1 *480 ) 1.5 * 480 / 1 = 720 D 4.0 320 (4/1 *320 ) 4 * 320 / 1 = 1280 E 1.0 520 (1/1 *520 ) 1 * 520 / 1 = 520 Aggregate Requirement 3280

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Review Question 1 Consider the three-stage process shown here with hourly capacity of each machine. What is the cycle time at Stage 1 20 +12 = 32 units / hr. 1/32 *60 = 1.88 min/unit What is the cycle time at Stage 2 8+10+12 = 30 units / hr. 60 * 1/30 = 2 min / unit. What is the cycle time at Stage 3 10+15 = 25 units / hr. 1/25 *60 = 2.4 min/unit Which stage is the bottleneck? Stage 3 has the longest cycle time (and lowest capacity) Stage Capacity (units/hr) Bottleneck 1 20 + 12 = 32 Stage 3, lowest capacity 2 8 + 10 + 12 = 30 3 10 + 15 = 25 ……………………………………………………………………………………………………… What is the minimum TPT? = 12 minutes Machine G1 P3 M2 Total Time (min) 3 5 4 12 (1/20 * 60) (1/12 *60) (1/15 *60) Suppose two new machines are added to the process (in parallel to other machines at a stage): P4 at stage 2 (with cycle time = 10 min / unit) and M3 at stage 3 (with cycle time = 6 min / unit). What is the process productivity? (There is one worker per machine). Capacity of P4 = 60 * 1/10 = 6 units / hr, capacity of M3: 10 units / hr. New capacities will be: Stage 1: 32, Stage 2: 30 + 6, Stage 3: 25 + 10. Bottleneck is at stage 1. Total number of workers = 2 + 4 + 3 =9. Productivity = 32/9 = 3.56 units per hr per worker. P1 8 P2 10 P3 12 M1 10 M2 15 G1, 20 G2, 1 2 Stage 1 Stage 2 Stage 3
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• Spring '10
• panwalker
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