Page 242 - Orlicky's Material Requirements Planning

C HAP TE R 12

Master Production

Schedule

A master production schedule (MPS) is to a material requirements planning (MRP) sys-
tem what a program is to a computer. The MPS is, technically speaking, only one of three
principal inputs to an MRP system (see Chapter 6), but whereas the other two, that is,
inventory status and product structure, supply reference data to the MRP process, the
MPS constitutes the input that “drives” it. It is the prime input on which an MRP system
depends for its real effectiveness and usefulness. MRP is the first step in the implemen-
tation of the overall manufacturing program of a plant, which is what the MPS repre-
sents. In the upstream/downstream relationship of information flow between systems,
the MPS is furthest upstream, and it acts as a wellhead of the flow of manufacturing
logistics planning information.
A given MPS is the determinant of future load, inventory investment, production,
and delivery service. It is the cause of certain inevitable consequences in the areas just
mentioned, and it may contain the seed of future problems and failures. As pointed out
in Chapter 6, downstream systems are unable to compensate for deficiencies of their
input. An MRP system will carry out its functions of inventory ordering, priority plan-
ning, and (indirectly) capacity requirements planning with great efficacy, provided that it
is presented with a realistic, valid MPS to be processed.

MASTER PRODUCTION SCHEDULING CONCEPTS
Does every manufacturing company or plant have an MPS? If such a schedule is defined
as the overall plan of production, it would be difficult to conceive of a plant operating
without one. In any manufacturing operation, the sum total of what a plant is committed
to producing at any given point in time is equivalent to an MPS. What some manufac-
turing managers really mean when they say that they do not have an MPS is that in their
case the overall plan of production is not being expressed in one formal document. For
purposes of MRP, the creation and maintenance of a formal MPS is a prerequisite.
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