What Is a Bill of Materials (BOM)?

What Is a Bill of Materials (BOM)?

A bill of materials (BOM) is an extensive list of raw materials, components, and instructions required to construct, manufacture, or repair a product or service. It lists the finished product at the top, followed by individual components and materials. Engineering BOMs are used in the design process while manufacturing BOMs are used in the assembly process.

Types of Bill of Materials (BOMs)

• Engineering BOM: Defines the design of a finished product. This BOM is commonly based on a computer-aided design (CAD) drawing. More than one BOM may be created as part of product lifecycle management.
• Manufacturing BOM: Lists all assemblies and parts required to complete all manufacturing activities to make a finished item. It also defines the required packaging materials to send the product to the customer.
  

Using a BOM

Manufacturers start the assembly process by creating a BOM. A bill of materials (BOM) is a centralized source of information, listing the items and instructions needed to create a product.

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. It includes all alternative and substitute part numbers and parts contained in the drawing notes.

Creating an accurate bill of materials ensures that parts are available when needed and that the assembly process is efficient. An inaccurate BOM can cause production delays if time is required to locate missing parts. This increases operating costs.

BOM Displays

A BOM displays its information in one of two ways: an explosion display or an implosion display. An explosion display defines an assembly at the highest level broken down into individual components and parts. A BOM implosion display links the lower-level parts to an assembly at the higher level.

For example, a computer is exploded into hard drives, chips, random access memory panels, and processors. Each processor is then exploded into an arithmetic unit, a 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 computer.

The Bottom Line

A bill of materials is an important part of the engineering and manufacturing process that lists the parts and materials required to build a product. An accurate BOM helps reduce waste, streamline production, and ensure the availability of necessary parts. Bills of materials help companies manage their operations costs.