Question

2. Four Step Process with Rework and Scrap - from module 5 slides Consider the following four step assembly operation with quality problems. All resources are staffed with one operator. The first resource has a processing time of 4 minutes per unit The second resource has a processing time of 3 minutes per unit. This process suffers from a high yield loss and 50% of all products have to be scrapped after this step. The third resource also suffers from quality problems. However, instead of scrapping the product, the third resource reworks it. The processing time at the third resource is 5 minutes per unit. In the 30% of the products in which the product needs to be reworked, this extends to a total (initial processing time plus rework) processing time of 10 minutes per unit. Rework always leads to a non-defective unit. No quality problems exist at the first and final resource. The processing time is 2 minutes per unit. a. For every unit of demand, how many units have to flow through the third step in the process? b. Where in the process is the bottleneck? c. What is the process capacity?

Answer 1

Answer:-

Yield every hour of the main resource = 60/4 =15 every hour

Yield every hour of the second resource =60/3 =20 every hour

Yield every hour of the third resource = 60/5 =12 every hour

Notwithstanding, out of these 12 units, 12x0.3 =3.6 should be worked upon once more, which will take a period of 10 min for each unit

Net time taken to deliver 12 units = 8.4x5 + 3.6x10 = 78 min

Net time per unit = 78/12 = 6.5 min

powerful yield = 60/6.5 = 9.23 every hour

(a) Since there is lost half in second step, there ought to be 2 units for every completed item going in the subsequent advance, however for each unit of demand, there ought to be one unit going through stage 3, as each unit will be modified.

(b) Third resource is bottleneck which has the least yield every hour

(c) The process capacity is 9.23 units every hour, which is equivalent to the capacity of bottleneck.

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