Model 3-1 was has been run for 8 hours (480 minutes) instead of 20 minutes. The plots on queue length and the number of times the drill press is busy or idle for the 8-hour run is given figure 1. Figure 1 (Simple Processing System with 8 hours of time)
The primary performance related results are compared in table 1. Table 1:
Performance Measures| 20 minutes run| 480 minutes run (8 hours)| Total Production| 5| 89|
Avg. Wait Time| 2.52| 3.33|
Avg. System Total Time| 6.43| 6.86|
Time-Avg. number of parts in queue| 0.78| 0.62|
Drill press utilization| 0.91| 0.65|
Note: For comparison purposes only average and not aggregate figures have been considered (except total production) * Total production as anticipated has increased in the longer run. However the drill press utilization has declined from 91 per cent to 65 per cent which indicates drill press under-utilization in the 8 hour run. * The average wait time has increased by 3/4th of a minute and the average system total time has also jumped by almost same margin. On an average parts arrive every 4 minutes in the 20 minutes case where as they arrive every 5.3 minutes on the 8 hour run. Hence the increase in wait time and total system time is most probably due to larger processing time per part at the drill press.
These results must be considered with caution because the system has been replicated only once. In order to have a meaningful estimate on system performance we have to consider multiple trials.
In the model 3-1, the set-up time at the drill press was assumed to be zero. Now consider a constant 3 minutes set-up times at the drill press for every part entering the process. The performance measures are expected to change and can be analyzed from table 2.
Performance Measures| Zero set-up time (20 minutes)| Constant set-up time of 3 minutes (20 minutes)| Constant set-up time of 3 minutes (2880 minutes)...