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Part Three
Planning and control
Table S14.3 Example of a level master production schedule including available to promise
Week number
1 2 3 4 5 6 7 8 9
Demand 10 10 10 10 15 15 15 20 20
Sales orders 10 10 10 8 4
Available 31 32 33 34 30 26 22 13 4
ATP 31 1 1 3 7 11 11 11 11
MPS 11 11 11 11 11 11 11 11 11
On hand 30
The bill of materials (BOM)
From the master schedule, MRP calculates the required volume and timing of assemblies,
sub-assemblies and materials. To do this it needs information on what parts are required for
each product. This is called the ‘bill of materials’. Initially it is simplest to think about these as
a product structure. The product structure in Figure S14.2 is a simplified structure showing the
parts required to make a simple board game. Different ‘levels of assembly’ are shown with
the finished product (the boxed game) at level 0, the parts and sub-assemblies that go into
the boxed game at level 1, the parts that go into the sub-assemblies at level 2, and so on.
A more convenient form of the product structure is the ‘indented bill of materials’.
Table S14.4 shows the whole indented bill of materials for the board game. The term
‘indented’ refers to the indentation of the level of assembly, shown in the left-hand column.
Multiples of some parts are required; this means that MRP has to know the required number
of each part to be able to multiply up the requirements. Also, the same part (for example, the
TV label, part number 10062) may be used in different parts of the product structure. This
means that MRP has to cope with this commonality of parts and, at some stage, aggregate the
requirements to check how many labels in total are required.
Figure S14.2 Product structure for the Treasure Hunt game