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Former Member

Mar 15, 2017 at 12:29 PM |
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Dear experts,

Please help me understand how ROC actually works, because I am really confused.

I have a material, which I have created the following ROC profile

For this material, the situation in MD04 is displayed as follows:

As you can see, the ROC profile was taken into account only for April where it produced 3 more pieces. I assume that this comes from the calculation:

ADR (average Daily Requirement) = Requirements/days = (30+30 for the 2 VSFs in March and April) / 61 (31 days in March and 30 in April) èADR = 60/61 = 0,983. This means that for April we have 3 days of coverage * 0,983 ADR = 2,949 therefore 3 pieces.

We observe that there is no additional coverage for March, which means that March is completely ignored. I assume this is because we are after the 1^{st} of March. However, if you check the Sums section of MD04, you will see that a ADR for March has been calculated, equal to 1,277. Why this ADR is different than the 0,983 that has been calculated earlier, since they refer to the same planning horizon of the 61 days of March and April?

The 1,277 figure can be produced as follows: today it is the 15^{th} of March, therefore we have 17 days left until the end of March. Plus, the 30 days of April, we have in total 47 days. Requirements are 60 (30 for March and 30 for April). Therefore, the ADR is 60/47 = 1,227. Is this logical? Since we are talking about the same period, should ADR change like this?

Now, I change the date of the first requirement to the current date and re-run MRP.

I see that ROC executed correctly this time (for both months). But again, I do not understand why it has produced different results for the two months. I was expecting it to suggest 3 pieces for both March and April, because, as we have shown earlier, we have 60 pieces for 61 days, therefore ADR = 0,983, which, multiplied with the 3 days of the target coverage it gives 3 more pieces in each month. If we check the Sums section, we will see that again, the ADR for March is different than the ADR of April. This leads to the calculation of 4 pieces of coverage in March and 3 days coverage in April:

If we do the same example by eliminating the March requirement, we see that system creates a coverage of 3 pieces for April but not in May. This means that the planning horizon is still March and April, but March is “ignored” since there is no requirement within this month.

Sums section on MD04 also seems logical

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