Page 237 - Orlicky's Material Requirements Planning

216 PART 3 Managing with the MRP System

PSEUDO-BOMS

When the BOM is broken down in the process of modularization, various subassemblies
are promoted and become end items, that is, highest-level items with no parent in the
planning BOM. This tends to create a large number of end items. Since it is the end item
that has to be forecast, and since the MPS has to be stated in terms of end items, the hun-
dreds (or thousands) of new end items would prove too many to work with. Fortunately,
there is a simple solution to this.
The objective always is to have the smallest possible number of items to forecast and
the smallest possible number of end items shown in the MPS. To meet this objective, the
technique of creating pseudo-BOMs is used. Going back to Figure 11-9, where the newly
created end items are grouped by option, there is no obstacle to taking any such group
and creating a pseudo-BOM (assigning an artificial parent) to cover it. This is illustrated
in Figure 11-10, where a new series of (pseudo) BOMs has been established.
These BOMs, sometimes called super-BOMs or S-bills, are an example of non-
engineering part numbers being introduced into a restructured BOM. An S-number, such
as S-101 in Figure 11-10, identifies an artificial BOM for an imaginary item that will never
be assembled. The sole purpose of the S-number is to facilitate planning. With the S-bills
established, when the transmission option in the tractor example is being forecast, only
S-102 and S-103 would be involved. These pseudo-BOM numbers then represent this
optional product feature in the MPS, and the MRP system will explode the requirements
from this point on, using the S-bills in the BOM file.
Another pseudo-BOM term in industrial use is the so-called kit number or K-num-
ber. This technique is used in some manufacturing companies where there are many
small, loose parts on level 1 in the product structure. These are often the fasteners, nuts,
bolts, and cotter pins used to assemble the major product units together. Under an MRP
system, to deal with such items individually on the MPS level would not be practical.

FIGURE 11-10
Super-BOMs.
Mechanical Power
Common Stick Shift Automatic Steering Steering

S-101 S-102 S-103 S-104 S-105

A13 C41 D12 L40 Z75

F28 P24 S36 B88 B62

E10 G53
R38 T65