Page 244 - Orlicky's Material Requirements Planning

CHAPTER 12 Master Production Schedule 223

FIGURE 12-1

A master production schedule (MPS).
Planning Horizon

Firm Tentative

Month A M J J A S O N D J F M A M J
Product
Hoist #35 50 50 50 60 60
Hoist #45 100 80 75 60 50
Hoist #55 200 200 200 150 150 100 100 100 150 150 200 250 250 250 250

Week
End Item 16 17 18 19
Motor 3848 60 60
Motor 4002 30 30 30 30
Drum 12-305 25 50

issues of an updated version of the MPS, however, there may arise a need for revision at
any time, as a result of the particular mix of new customer orders and the various
unplanned developments in procurement and manufacturing. It is highly desirable,
therefore, for the MRP system to be able to process intervening and intermittent “unoffi-
cial” changes in the MPS on a more frequent basis than that afforded by the forecasting
cycle. As discussed in Chapter 14, an MRP system loses much of its effectiveness if it is
not used to replan daily. Arguments for continuous replanning of material requirements
were presented in Chapter 7.

THE FINAL ASSEMBLY SCHEDULE
In order to comprehend the essence and the true function of the MPS, a distinction must
be drawn between it and the final assembly schedule. This was touched on earlier in con-
nection with other topics, but at this point, a more thorough discussion is warranted. The
distinction between these two schedules is a source of frequent confusion because in
some cases the schedules, although always different in concept, may be identical in real-
ity; that is, the final assembly schedule may serve as the MPS.
There may be no difference between these two schedules where the product line is
limited or where the product itself is small and/or simple. Lawnmowers, hand tools,