In this question you will study the effect that variability can have on the behaviour of a simple production system, using computer simulation as a tool to gain insights that can be applied to more complex systems. The system under study is a three-stage production line with stations named Joe, Next, and M3. Processing times at stations have an average of 6 minutes, with variability following the Shifted Exponential distribution (already entered in the model). Buffers are used to cushion the impact of variability to some extent, by holding the output of one station while waiting for its processing at the following station. It can be assumed that Joe will always have something to work on, and M3 can always deposit finished output in a Shipping storage area.

Though this situation is set in a production environment, several services also operate as series of operations with intermediate queues (e.g. a cafeteria line), which is what the simulator tries to model. The questions given below are to be answered using the Linesim Excel-based simulator.

1. How many units would you expect to be able to ideally produce per hour on the average?
2. How many units did you actually produce per hour on the average? Explain any difference between your simulation results and your estimate made in (a)? Also tabulate the average utilizations at each machine, and compute the mean and standard deviation of system output (data for which can be extracted from the Machines worksheet).
3. Diagram the impact of changing the buffer stocks on the output of the system by changing the storage area capacity cells (e.g. the buffer between Joe and Next is changed by changing Joe's Output storage capacity). Consider buffer levels that vary from 0 to a maximum of at least 20 units. What can you conclude from these experiments?
4. What would be the impact on system performance if machine M3 had a processing time that averaged 7.5 minutes (assuming Joe and Next still run at an average of 6)? What happens to the inventories after Joe and Next? Does varying the size of these buffers have any impact?
5. What happens if Joe is the bottleneck (i.e. 7.5 minutes) instead of M3? Do the buffers at Joe and Next have any impact?