ITPEC IP October 2018 Question 89
A factory is engaged in assembly production of product P that consists of components A and B. The processing of component A requires component C, and the processing period is one week. The delivery lead times of purchased components B and C are two weeks and three weeks, respectively. Product P can be assembled in one week only after components A and B are both delivered. What is the minimum number of weeks required to produce one unit of product P, including the delivery periods of the components? Here, there is no stock of any of the components.
Explanation
5 weeks — the longest chain of dependent steps, C → A → P, sets the time; B is ordered at the same time and waits.
- •Component C is delivered after 3 weeks, and processing it into A takes 1 more: A is ready after 3 + 1 = 4 weeks
- •Component B is ordered at the start and delivered after 2 weeks, well before A is ready
- •Assembly of P starts when both A and B are there, at week 4, and takes 1 week: 4 + 1 = 5 weeks
Answer (b)
Why not others:
- •(a) 4 — stops when A is ready and leaves out the 1-week assembly of P
- •(c) 6 — no chain of steps is 6 weeks long: C → A → P takes 5 and B → P takes 3, so a sixth week can only come from waiting unnecessarily
- •(d) 7 — adds every duration in sequence, 2 + 3 + 1 + 1 = 7, as if B could only be ordered after C arrived, instead of ordering both at the start
Key rule: Lead times of parts ordered in parallel do not add; the product's lead time is the longest path through the bill of materials, as MRP uses it to schedule orders.
Business Industry · AI-written, may contain errors
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