What Is a Bill of Materials (BOM)?

A bill of materials (BOM) is an extensive list of raw materials, components, and assemblies required to construct, manufacture or repair a product or service. A bill of materials usually appears in a hierarchical format, with the highest level displaying the finished product and the bottom level showing individual components and materials.

There are different types of bills of materials specific to engineering used in the design process; they're also specific to the manufacturing used in the assembling process.

Understanding Bills of Materials (BOM)

The different types of bills of materials depend on the projected use and business needs. A manufacturing BOM is essential in designing enterprise resource planning (ERP) systems and materials requirement planning (MRP).

A bill of materials explosion displays an assembly at the highest level broken down into its individual components and parts at the lowest level, while a BOM implosion displays the linkage of individual parts at the lower level to an assembly at the higher level.

For example, a computer is exploded into hard drives, computer chips, random access memory panels, and processors. Each processor is exploded into an arithmetic unit, control unit, and a register. The requirements for the arithmetic unit, control unit, and register are imploded into the requirements for the processor, which are imploded into the requirements for the entire computer.

[Important: The different types of bills of materials depend on the projected use and business needs.]

A bill of materials is a centralized source of information used to manufacture a product. It is an engineering term that refers to the design of a product. Manufacturers that build products start the assembling process by creating a BOM. Creating an accurate bill of materials is vital because the correct parts must be available when the item is manufactured.

If it is not accurate, it can cause production to halt or cause delays, which increase operation costs because a company has to locate the missing parts, start another production order or deal with customer returns.

Types of BOM

A BOM list is necessary when ordering replacement parts and reduces possible issues if product repairs are required. It helps to plan for acquisition orders and reduces the possibility of errors.

An engineering bill of materials defines the design of the finished product. It includes all alternative and substitute part numbers and parts contained in the drawing notes. Every line of the bill of materials includes the product code, part name, part number, part revision, description, quantity, unit of measure, size, length, weight, and specifications or features of the product.

The engineering BOM is often organized by engineers based on a computer-aided design (CAD) drawing. For a finished product, there may be more than one engineering BOM created. This is a part of product lifecycle management.

A manufacturing bill of materials comprises all the assemblies and parts required to construct a finished item ready to be shipped. It also incorporates the packaging materials required to send the product to the customer. It contains processes that require execution on the product prior to completion and stores all the information required for manufacturing activities.

Key Takeaways

  • The different types of bills of materials depend on the projected use and business needs of the individual project.
  • A BOM is a centralized source of information used to manufacture a product.
  • A bill of materials is often shown in a hierarchical way, from the finished product all the way down to individual components and materials.