Consider the School Chairs Mini-case at the end of Chapter 6. Suppose the seat is made in a seat-fabrication work centre, all other parts (posts, cross bars, rails) are made in a post-bar-rail work centre, and tire chair is assembled in the chair-assembly work centre. Suppose that a chair takes 15 minutes to assemble and uses 1 seat and one kit of other parts (2 front posts, 2 back posts, 10 cross bars, and 3 rails). A seat takes 5 minutes to make from half a plank (a plank is 2" by 4" by 8'). Assume that glue will be dried overnight. A kit of other parts takes 10 minutes to make from 1 plank. Suppose each work centre is staffed by one worker who works 8 hours a day, 5 days a week (Mon-Fri), and that we promised 90 chairs to a school to be delivered on Friday, December 12.
a. Determine the manufacturing lea d times (in day) for assembling 90 chairs, making 90 seats, and making 90 kits of other parts. Round up if a fraction of day is used.
b. There is no inventory' on hand or on order, no safety stocks are needed, lot-for-lot ordering is used, and purchase lead time for lumber is one workday. Use MRP to determine when and how many units of lumber to purchase, seats to make, other parts to make, and chairs to assemble.
c. What action should be taken now?
d. If we have 35 planks on hand, how would your answer change?
e. If we have 35 planks on hand and we order lumber in batch size of200 planks, how would your answer change?