Page 476 - Orlicky's Material Requirements Planning

454 PART 4 Looking Backward and Forward

better chance there is that it will finish early or at least on time. This assumption is most
often completely false. Launching purchase orders (POs) and manufacturing orders
(MOs) as early as possible exposes the company to risk associated with design changes;
unnecessarily consumes cash, capacity, and materials; and chokes the manufacturing
floor with unnecessary work-in-process. Employing the suggested DDMRP method stag-
gers and chokes the release of POs and MOs in such a way that will minimize those risks
while at the same time better protects and manages the critical timing needs of the end-
item order.

DECOUPLED EXPLOSION
The BOM explosion is still a critical and necessary element of planning in environments
of even moderate complexity. Without exploding the BOM, there is no visibility of total
requirements. This is why MRP proponents in complex environments continue to use
MRP and claim that without it there is no chance at flexibility and agility.
In DDMRP, component-part requirements are still calculated by exploding down
through the BOM. However, this planning is decoupled at any buffered component part
(i.e., replenished, replenished override, or min-max). These parts then will explode when
they reach their respective rebuild zones. Figure 26-26 shows the decoupled explosion for
the earlier example Part FPA. Note that whenever a buffer position is encountered, the
BOM explosion stops. The figure on the left depicts the explosion for the parent item FPA
after its available stock position has been driven into the yellow zone. The middle figure
represents buffered components that explode independently when they have reached
their respective rebuild zones. Finally, there is the explosion for subassembly B (SAB)
after its available stock equation has been driven into yellow.