Page 251 - Orlicky's Material Requirements Planning

230 PART 3 Managing with the MRP System

od 10 corresponds to whatever period the product would appear in the MPS, and the
overall fabrication load it generates is distributed over eight periods (the product’s fabri-
cation lead time) preceding the completion date. The figure shows a load profile for the
same product related to heavy presses, a critical resource or bottleneck.
A load profile is computed by using the MRP system as well as the operations sched-
uling and loading systems as simulators. The quantity of one each of the end items mak-
ing up the product (using a typical combination of optional features), arbitrarily assigned
to some future period, is processed by the MRP system using blank inventory records or
a special program routine suppressing the netting function. The gross requirement of one
is exploded through all levels of the product structure, bypassing any lot-sizing computa-
tions. The resulting output is a planned-order receipt schedule (all minimum quantities)
for all items at whatever level that would be used in the production of one each of the end
items in question. These planned-order schedules then serve as input to the regular sched-
uling and loading systems, and using whatever scheduling rules and loading conventions
are in effect, a special load report is generated. This load report, when summarized, rep-
resents the product load profile, which then is stored for future use.
In developing the load profile, the treatment of setup time will vary depending on
whether setup standards exist, that is, whether setup is considered direct labor or over-
head. Where the routings contain setup standards, setup hours are part of the load pro-
file created by the method just discussed. The setup load, however, is stored separately
from run-time load because of the different treatment each will receive when the total
load for a product lot is calculated. If setup standards are not maintained, empirical
setup-hour data can be apportioned to the respective run times, or else the latter can be
increased by some percentage to account for setup.
The final load profiles of all products are stored so that they can be used repeatedly
in resource requirements planning without a need for the detailed computation. The
development of product load profiles is a one-time job. Unless the product in question is
redesigned drastically, its load profile will serve throughout product life because engi-
neering changes normally would have only a trivial effect on the load involved.
Extending load profiles by the quantities called for by a given (version of the) MPS
and summarizing them by period are simple matters. They are accomplished very quick-
ly with a computer that has access to the file in which the profiles are stored. The result
is a report (printed or conveyed through a visual-display device) showing the effect of the
MPS over the entire planning horizon on the various resources for which profiles are
maintained. These are called resource requirement profiles. They provide a fair indication of
the loads that can be expected. The loads may be segregated by individual product lots
to show which of these are causing potential capacity problems. This is portrayed graph-
ically in Figure 12-3.
Note that load generated by service-part and interplant requirements is added to
that derived from product lots. This could be an empirically verified percentage of the
load, it could be forecast, or it might be computed through separate load profiles if the
service-part and/or interplant items are large and their demand significant.