Examples: BOMs and Future Data in MRP Planning 
Example 1
When inspecting parent item demands in a future period that is beyond the planning horizon, the MRP takes these demands into consideration to calculate order recommendations for the child items involved. However, in the final result, the MRP generates only order recommendations within the planning horizon. The example below demonstrates this scenario.
A parent item, PBOM1, is made from three child items: C1, PBOM2, and C3. PBOM2 is made from an assembly BOM, ABOM1, which is assembled from child item C2 – as per the bullet structure below:
PBOM1 (Production BOM; Lead Time: 1 Day)
C1 (Lead time: 1 Day)
PBOM2 (Production BOM; Lead Time: 2 Days)
ABOM1 (Assembly BOM; Lead Time: Not Relevant)
C2 (Lead Time: 2 Days)
C3 (Lead Time: 3 Days)
The planning horizon for this MRP run is from October 22 to October 26, and there is a sales order requirement for PBOM1 due on October 30. The following table shows the demands schedule after calculating the lead time in MRP.
Note
In the tables below, OR is short for order recommendation.
10.22 |
10.23 |
10.24 |
10.25 |
10.26 |
10.27 (Future) |
10.28 (Future) |
10.29 (Future) |
10.30 (Future) |
|
|---|---|---|---|---|---|---|---|---|---|
PBOM1 |
OR |
Requirement from sales order |
|||||||
C1 |
OR |
||||||||
C3 |
OR |
||||||||
PBOM2 |
OR |
||||||||
ABOM1 |
|||||||||
C2 |
OR |
The MRP generates only order recommendations that fall within the planning horizon. Therefore, in this case, the MRP generates order recommendations for C2 on October 25 and C3 on October 26, and ignores recommendations for other items in the BOM chain.
Example 2
When the MRP cannot create order recommendations in time to satisfy the demands due to the lead time required, the MRP adjusts the order recommendation to the earliest and possible date within the planning horizon. The following example demonstrates this scenario.
A parent item, PBOM1, is made of three child items: C1, PBOM2, and C3. PBOM2 is made from an assembly BOM, ABOM1, which is assembled from child item C2 – as per the bullet structure below:
PBOM1 (Production BOM; Lead Time: 5 Days)
C1 (Lead time: 1 Days)
PBOM2 (Production BOM; Lead Time: 2 Days)
ABOM1 (Assembly BOM; Lead Time: Not Relevant,)
C2 (Lead Time: 2 Days)
C3 (Lead Time: 3 Days)
The planning horizon for this MRP run is from October 22 to October 26, and there is a sales order requirement for PBOM1 due on October 30. The following table shows the demands schedule after calculating the lead time in MRP.
10.21 (Past) |
10.22 Current System Date |
10.23 |
10.24 |
10.25 |
10.26 |
10.27 (Future) |
10.28 (Future) |
10.29 (Future) |
10.30 (Future) |
|
|---|---|---|---|---|---|---|---|---|---|---|
PBOM1 |
OR |
Requirement from sales order |
||||||||
C1 |
OR |
|||||||||
C3 |
OR |
|||||||||
PBOM2 |
OR |
|||||||||
ABOM1 |
||||||||||
C2 |
OR |
We can observe that the recommendation for C2 is on October 21, a day before the current system date. The MRP cannot generate order recommendations in the past; therefore, the MRP moves the schedule to the earliest possible future time, and that is October 22.
After the MRP delays the recommendation for C2, the entire planning schedule has to be moved to one day later to satisfy the lead time requirements. In this case, PBOM1, the item on the top level of this BOM chain, is finally recommended on October 26. Since PBOM1 requires a lead time of 5 days, the supply of this item is on October 31, which is one day late for the due date of the sales order.