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Lead time scheduling problem

Dear colleagues:

Problem statement: Although we choose to perform leadtime scheduling in MRP, the system still reads inhouse production time, to determine direction of scheduling.


The specific symptoms & MRP behavior are as follows

1) If the duration of inhouse production time is not long enough, such that the start date of the production order falls in to future from Today's date, then the system performs BACKWARD scheduling using the routing

2) If the duration of inhouse production time is long enough, such that the start date of the production order falls in past from Today's date, then the sytem performs FOWARD scheduling using the routing.

The business impact of this is causing several of our planned orders to be unncessarily 'Rescheduled in' or moved much earlier than requirement dates.


At the outset, the above symptoms may appear that this is standard functionality but upon close examination, there seems to be quirks to the way lead time scheduling in MRP works. Let me explain further.

The master data and configuration that we are using is as follows.

1. Start date in Past - Disallowed in Configuration

2. Inhouse production time ~ 80 days

3. Routing ~ 2 days

4. Reduction strategies used - YES

We recognize that 2 & 3 above are not in sync and it is not a common best practice. The client uses long lead times in material master to accommodate the total replenishment time of the product ahead of the routing creation.

Here are the questions -

1. Does MRP always perform basic scheduling as a first step, even if we choose lead time scheduling?

Is this a standard logic?

2. How do we force MRP to look at ONLY routings and not to look at INHOUSE PRODUCTION TIME

for determining the direction of scheduling when we perform Lead time scheduling?

Thanks and regards,


Former Member
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