This question illustrates the effect of different levels of
variability in a serial production system. Use the three station
simulation (Three Station_CV.mox) that measures coefficient
of variation (COV) in the Examples/Models and Methods
folder. For each case use two different policies for releasing
raw materials to the system:
Raw Material Release Policies
- Material is released to the first station with a constant
interval between releases of 5 minutes.
- Material is released to the first station with the interval
between releases having an exponential distribution with mean
time of 5 minutes..
Processing Time Assumptions
The processing time at each station is governed by a non-central
Beta distribution with the parameters alpha = beta = 5. The
mean processing time is 4 but the alternatives below have different
- The range of the Beta distribution is 0 to 8. COV = 0.447.
- The range of the Beta distribution is 2 to 6. COV = 0.224.
- The range of the Beta distribution is 3 to 5. COV = 0.112.
a. For the 6 combinations of raw material release policies
and processing time assumptions, make 10 simulation runs of
1000 minutes each. Measure the average cycle time in each case.
Compare the results and rank the runs according to increasing
b. For the 6 combinations of raw material release policies
and processing time assumptions, use the formulas for non-Poisson
queuing networks from Chapter 17 to compute the average cycle
time in each case. Compare the results and rank the runs according
to increasing cycle time. Compare the results from the simulation
of part a. Comment on the accuracy of the approximate analytical
c. Simulate the system when the release time and all processing
times are exponentially distributed. The average time between
material release is 5 minutes and the average processing time
at each station is 4 minutes. Make 10 simulation runs of 1000
minutes each. Use the formulas for the Jackson network to compute
the cycle time and compare the simulated and analytical results.
Which results are more accurate?