Bill of Materials 

Bill of Materials (BOM) is an important document for any project, production before launching or material requirement planning process. 

The American Production and Inventory Control Society (APICS) defines a BOM as "a listing of all sub assemblies, intermediates, parts and raw materials that go into making the parent assembly showing the quantities of each, required to make an assembly". 

BOM serves the following purposes: 

?  It specifies the components required for a project. 

?  It provides a platform for recording the engineering changes in parts consequent to change in design. 

?  It is a ready beckoner for purchase parts and manufactured parts for the end product. 

?  It provides a list of parts required to make a subassembly, assembly and final product. 

?  It can participate as costing a tool. 

Identification of parts is an important requirement in preparation of BOM. Each part that goes into a product is identified by unique part number, which is not assigned to any other part. A part with the same material, shape, but with different finish, like painting  instead of plating, is assigned a different number. In conclusion, BOM can be described as a summarised parts list for making one set of complete assembly. 

BOM is further exploded to arrive at the total quantitative requirement of a part/component for batch quantity. If the part under reference has multiple uses in different products, that is, in manufacture of variants of the same product, then the requirement is assessed across the variants to arrive at a quantity. The quantity thus arrived is termed as  gross requirement. In a project running continuously over a period, the situation is highly dynamic as a few numbers of this part may be available in stock within the plant and few pieces ordered earlier may be in pipeline (that is in transit). Hence, all these quantities are taken into consideration before arriving at net requirement for either manufacture or supply.