Page 288 - Orlicky's Material Requirements Planning

CHAPTER 14 System Effectiveness: A Function of Design and Use 267

FIGURE 14-3
Week
A planned order Lead Time: 3
mature for 61 62 63 64 65 66
release.
Gross Requirements 15 20 20 10
Scheduled Receipts 20
On Hand 27 12 12 12 –8 –18 –18
Planned-Order Releases 20

Action Bucket

cause a problem at the level of component material that has been planned by the MRP
system to cover requirements of perhaps several parent planned orders in quantities that
the system planned for these orders. If the planner exceeds one of these quantities, he or
she may short another one.
In net-change MRP systems (see Chapter 7), changing planned-order quantities at
the time of shop-order release means upsetting the interlevel equilibrium that the system
continuously strives to maintain. Such changes in effect introduce errors into the system’s
records that the planner should correct immediately (through special transactions) if he
or she must override the system’s recommendation. Note that the preceding comments
pertain to shop orders; planned purchase orders are not as critical because they do not
involve component materials within the system. When the planned order shown in
Figure 14-3 as mature is released, the transaction reporting this will change the status of
the item to that shown in Figure 14-4.
At this point, both open orders are scheduled correctly, that is, aligned against the
dates of need. If the gross requirements change subsequently, however, the dates of need

FIGURE 14-4 +20

Status change
following planned-
order release. Week
61 62 63 64 65 66
Gross Requirements 15 20 20 10

Scheduled Receipts 20 20
On Hand 27 12 12 12 12 2 2
Planned-Order Releases

–20