HAL computer has a printed circuit board line with 2 stations. The first station (resist apply) applies a photoresist material to the circuit boards. The second station (expose) exposes the boards to UV radiation to produce a circuit pattern that is later etched onto the boards. Analysis of the line shows that resist apply has an average process time of 35 min with a coefficient of variation of 0.8, and expose has an average process time of 30 minutes, with a coefficient of variation of 1.2, In addition and not included in the process times, resist apply has a MTTF of 70 hrs and an MTTR of 3.5 hours both based on an exponential distribution,while expose has a MTTF of 5 hrs and MTTR of 20 min,. Jobs arrive at the resist with anarrival rate of 1.5 jobs per hour, with an arrival coefficient of variation of 1.6.
a. Compute the effective process time at Station 1 (resist apply)
b. Compute the effective process time at Station 2 (expose)
c. Compute the effective SCV at Station 1 (resist apply)
d. Compute the effective SCV at Station 2 (expose)
e. Compute the average waiting time at Station 1
f. Compute the average waiting time at Station 2
g. Compute the average WIP level in queue at Station 1
h. Compute the average WIP levels in queue at Station 2.
i. What in your opinion is the cause for the high queue time at Station 2.
j. Because the expose operation must take place in the clean room, the engineers will have to limit space for the WIP between the 2 stations to 4 jobs. After limiting the WIP, they find the line to be incapable of achieving the target throughput of 1.5. Explain why they are unable to meet the target throughput.