Common use of Lead-time To-Be Clause in Contracts

Lead-time To-Be. In the Lead-time To-Be situation, almost the same parameter values as in the Min-max As- Is situation are used. The values for turn-around stock and the threshold level are changed with respect to the Min-max As-Is situation. The turn-around stock and the threshold level are calculated using the optimization problem which is used to determine this parameter setting, see Chapter 5. To solve this optimization problem, an Excel sheet using Visual Basics is made. This sheet is verified by comparing the sheet to a program which is developed by ▇▇▇▇▇▇▇ ▇▇▇▇ at the same moment and which would generate the same results. The calculation time of the program I made was sufficient longer than the program developed by ▇▇▇▇▇▇▇ ▇▇▇▇, therefore for generating results ▇▇▇▇▇▇▇▇’ program was used. For all parts the investment cost, the repair time and the demand rate are needed as input for the optimization model. The values of these parameters are obtained from data of NedTrain; for the exact values see Appendix J. Other parameters needed are the maximum number of the EBO, maximum percentage of parts which can get an emergency lead-time, the emergency lead-time and the regular lead-time. The values of these parameters and the reasoning behind these choices are explained in the next paragraphs. 6.1. In this table the values for the average throughput times and the standard deviation, for different utilization rates are displayed. A gamma distribution is fitted on the mean and standard deviation. This is done using: a = E[X]/b and b = V [X]/E[X]; the values of a and b are displayed in Table 6.1. Hereafter, the 95 percentile of the throughput time is calculated. This is the value for which 95% of the throughput times are smaller than this value. For the remaining calculations we choose to use, the 95 percentile of the throughput time by a utilization of 0.99; 87. This is done because 0.99 is the highest utilization rate. The reasoning behind this choice is that in this case the value can be used for all utilization rates because overestimation is less severe than underestimation. To determine the emergency lead-time and the regular lead-time the 95 percentile is used, see Formula 6.3. In the formula, the lead-times are weighted based on their occurrence. Only 20% of the parts get an emergency lead-time and 80% of the parts get a regular lead-time. The weighted lead-times, must be equal to the 95 percentile of the throughput time. For the Le in the simulation models, the repair times multiplied with 1.001 is used. This is done to take an emergency lead-time which is almost equal to the average repair time of a part. For the calculations of the Lr, Le = 16.4 is used, since this is the average repair time of all parts. Solving the equation, results in Lr + Le = 88