Littlefield Simulation Write-up
December 7, 2011
Operations Management 502
Team 9
Littlefield Lab
We began our analysis by searching for bottlenecks that existed in the current system. It was easily identified that major issues existed in the ordering process. Without calculations, you could tell the reorder point was too low since the historical plots showed inventory levels at zero for two or more days at a time. The number of jobs in customer orders showed correlating spikes at the same time of the inventory outages. We reviewed the utilization and queues of the other stations in the system but were hesitant to make in immediate changes since we were not entirely certain the effects of correcting the inventory policy.
To correct
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We recalculated the average arrival rate over the entire simulation to be approximately 11.8 orders per day, which we rounded to 12 for a small buffer. Based on this daily consumption, we found what day the next reorder point would be which was day 222. We wanted to find the demand for the final 46 days with an average of 12 orders per day came up with a figure of 552 units needed to meet demand over the last 46 days. Since we already had 61 units at the time of ordering, we subtracted that figure from the 552 and came up with a final order value of 491. This value should allow us to have a low inventory level at the end of the simulation. To achieve this, we had to change the reorder point to zero. This strategies hinges heavily on the lab not being in existence past day 268, if that were not the case, we would not recommend this plan.
How to reach our optimal decisions and what is the operations statistics after optimization?
1)
Rough approximation of the machine service rate μ based on the statistics from first 5 days:
Station
1
2
3
Arrival Rate = Th = λ (jobs per day)
12.24
12.24
12.24
Machines
3
1
1
Utilization of station
90%
94%
70%
Machine service rate μ = λ/(m*Utilization)
(jobs per day)
4.533
13.021
17.486
2)
Approximate lead time improvements in optimized plan (via lowest M increase for max Lq improvement)
Original Plan
Optimized Plan
Station
1
2
3
1
2
3
Arrival Rate =
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