Bill of Material and BOM
A bill of materials or bill of material (BOM) describes a product in terms of its assemblies, sub-assemblies, and basic parts. Basically consisting of a list of parts, a BOM is an essential aspect of the design and manufacture of any product.
Often, BOMs contain hierarchical information with the master BOM (top level BOM / parent BOM) describing a list of components and sub-assemblies. For instance, consider a PC, for example: the top level BOM might list the shipping box, manual, packaging and the actual PC itself. The BOM for the PC itself is referenced in the top level BOM and would contain its own list of sub-assemblies like power supply, motherboard, case, etc. This increasing level of detail continues for all sub-assemblies until it reaches its constituent parts (like processors, chips etc), or modules that are out of the scope of the BOM (i.e. the parts that make up the power supply that is a bought-in item from another manufacturer).
BOMs are important, since without a basic knowledge of how many parts a product needs, there is no way of knowing how many units of that part you need to buy. A bill of material can define products as they are designed, as they are manufactured, as they are ordered, as they are built, or as they are maintained. There are different types of bills of materials dependent upon the discipline that generates them and the purpose for which they are intended. It is important to ensure the type of bill of material that you have and its intended use prior to working with a bill of material.BOM accuracy is a problem for production planning systems such as MRP, MRP II and ERP.
