Page 188 - Orlicky's Material Requirements Planning

CHAPTER 9 System Records and Files 167

FIGURE 9-3
Period
Treatment of
quantities past A Parent Past Due 1 2 3 4
due.
Planned-Order Releases 12 5 18 20

Component

Gross Requirements 12 5 18 20
Scheduled Receipts 10 15
On Hand 36 44 44 26 6
Planned-Order Releases

B Parent
Planned-Order Releases 12 17 18 20

Component
Gross Requirements 12 17 18 20
Scheduled Receipts 10 25
On Hand 36 44 44 26 6

Planned-Order Releases

The respective quantities are recorded as past due either as a result of the lead time
exceeding the available time in the case of planned-order releases or because of lack of
planned performance in any of the schedules. If the master production schedule (MPS)
that is being input to the MRP system for processing contains past-due buckets, it also
will cause quantities on component levels to be timed as past due. The past-due timing
in the time-phased inventory record should be avoided except where it may aid in fol-
lowing up and expediting behind-schedule performance on open-order completions and
planned-order releases. Recording a planned order as past due when there is insufficient
time left for the full lead-time offset, as shown in Figure 9-4, makes little sense because
there is no delinquent performance involved that should be expedited, and the order-
release action cannot take place in the past but only in the present, that is, in the current
period. This situation is mitigated with establishment of the necessary strategic buffers to
protect manufacturing from demand and supply variability. See Chapters 4 and 22 for
how these buffers are established.
It is possible to time phase past-due quantities and to display them in the invento-
ry record, as shown in Figure 9-5, but there is little benefit to such practice. A past-due