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1) You are a supplier of printed circuit boards (PCBs). Production of the circui

ID: 396539 • Letter: 1

Question

1) You are a supplier of printed circuit boards (PCBs). Production of the circuit boards consists of several steps – Surface Mounting, Baking, and Final Assembly. Surface Mounting puts integrated circuits (ICs) and other components on a PCB. These PCBs are then Baked as a batch and kept in an oven for some time so that the ICs are soldered onto the PCBs. Finally, these PCBs are taken and manually assembled into a case, and wired with connectors. The processing rate at the Surface Mounting station is 15 PCBs/minute, the processing rate for Baking is 5 PCBs/minute, and the processing rate for Final Assembly is 3 PCBs/minute.

If there are on average 24 units of (work in process) inventory and the system is working at capacity, what is the flow (throughput) time for PCBs?

2) Steel City Juice is a local company that makes two kinds of juice: orange juice and apple juice. Demand for orange juice is 60 barrels/hr, while demand for apple juice is 40 barrels/hr. The company only has one machine to extract juice from raw fruit. The machine can extract orange juice at a speed of 150 barrels/hr, or apple juice at 120 barrels/hr. Switching from one type to the other requires 30 minutes cleanup time.

a. Please provide a production schedule and an associated process flow diagram that

(i) cycles repeatedly through the two kinds,

(ii) meets the required demand, and  

(iii) minimizes the amount of inventory held. (Here it is assumed that the production machine runs 24 hours a day, 7 days a week)

b. What is the maximum inventory level of orange juice?

3) In 2006, Shouldice Hospital admitted 14,965 patients. In 2007, a 20% increase in admissions is expected. Currently the hospital has 390 beds. Assume the hospital operates 365 days a year (and, please assume one patient per bed!).

i. If the average patient stays in the hospital 8 days, how many beds were empty, on average, in 2006?

ii. On average, how many beds do you expect to be empty in 2007?

Explanation / Answer

Answer 1:

Given: WIP= work in progress inventory = 24 units

Calculation of Lead time or time spent to make the PCBs,

Operation Surface mounting is done at the rate of 15 PCB/ min. Therefore, time taken by one PCB at the SM operation = 1/15 min

Operation Baking is done at the rate of 5 PCB/ min. Therefore, time taken by one PCB at the Baking operation = 1/5 min

Assembly is done at the rate of 3 PCB/ min. Therefore, time taken by one PCB at the assembly = 1/3 min

Therefore, total time taken = (1/15) + (1/5) + (1/3)

                                            = 3/5 mins

Now, by Little’s Law

Work in progress = Throughput * lead time

24 units = Throughput * 3/5 mins

Throughput = 40 units per minute