Time Phased Planning
Time-phased planning is an MRP procedure where the materials are planned in a particular time interval. If for example, a vendor always delivers a material on a certain weekday, then it makes sense to plan this material according to the same cycle, adjusted to the delivery date.
To plan a material with time-phased planning, it is a must that the MRP Type shall be entered in the material master record for time-phased planning and the planning cycle. The latter is defined in the form of a planning calendar in the Planning Cycle field.
For time-phased planning materials, the planning file entries NETCH and NETPL in the planning file are not important, so are not set for MRP changes. Materials that are planned according to a time-phase are provided with an MRP date in the planning file. This date is reset on the creation of a new material master data, and then after every planning run. This date corresponds to the day that the material will next be planned; it is calculated on the basis of the planning cycle specified in the material master. The material will only be planned on the days that have been specified by the planning cycle. Noted that to have control of this procedure and plan a material before the intended MRP date, it is possible to specify a MRP date in the planning run. For example, if the MRP run is planned for Monday, it is probable to execute the run for Monday on Saturday.
The lot-sizing procedure for a time-phased planning material is the exact lot size, so optimizing lot-sizing procedures can also be applicable for time-phased planning.
Triggering Planning Run
When the planning run is triggered, the system uses the MRP date in the planning file to check whether the materials are to be planned. The MRP date is calculated from the planning cycle. The system calculates the requirement. It also determines a time interval according to the following algorithm:
MRP date + planning cycle + purchasing processing time + planned delivery time + goods receipt processing time.
The system compares the forecast requirement in this time interval with the stock and both the fixed and firm receipts in this time interval. It then calculates the quantity to be ordered. During calculation, the system assumes that the fixed receipts lie at certain intervals. It does not matter whether the fixed receipts are available at the start or at the end of the interval. This means that there may be a temporary shortage.
Noted that Time-phased planning can be combined with a reorder point. The material is not only planned on the MRP date in the planning file, but also when the reorder point is fallen short of due to a good issue. If the reorder point has a shortage, the material is flagged for planning, as is the planning cycle. During requirements calculation, the system creates a time interval that spans from the time of the reorder point shortage to the availability date of the next regular MRP date. For this time interval, the ordered quantity must suffice. On the next MRP date, the material is again planned at regular intervals.
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