Page 189 - Orlicky's Material Requirements Planning

168 PART 2 Concepts

FIGURE 9-4
Period
Past-due order
release caused Lead Time: 5 Past Due 1 2 3 4
by insufficient
lead time. Net Requirements 25
Planned-Order Releases 25

FIGURE 9-5
Weeks Past Due Week
Time-phased
quantities past 4+ 3 2 1 34 35 36 37
due.
Scheduled Receipts 6 50 60

order (assuming that its due date is valid) is past due and needs to be expedited for ear-
liest possible delivery—irrespective of how much past due it is. Its original due date can
be carried in the subsidiary segment of the inventory record. The status segment of this
record is being unnecessarily complicated by the inclusion of several past-due fields.
In MRP systems of the net-change variety, the function of the past-due field is taken
over by the control-balance bucket, in which both delinquent and premature perfor-
mance is being recorded in terms of, respectively, positive and negative values. The last
special field in the status segment of the inventory record that merits brief mention is the
total bucket, which appears at the end of each time-bucket row. Inclusion of this field is
optional. It would be used for purposes of reconciliation or a validity check of the status
data that the computer would be programmed to carry out whenever the net require-
ments are recomputed.
For example:
Current on hand: 115
Total scheduled receipts: 100
215
Allocated on hand: 35
Total gross requirements: 380 –415
Total net requirements: –200
Total planned orders: 225
Planned coverage excess: 25
This type of reconciliation will detect irregularities in the status data or conditions
calling for scrutiny and possible action. For example, if the projected on-hand quantity
(equivalent to net requirements) at the end of the planning horizon is a positive value
(“negative” net requirements), it is indicative of excessive coverage, probably caused by
a reduction in gross requirements. If there are any open orders outstanding, they should
be reduced or canceled, if possible.