A bill of materials (BOM) is a detailed inventory of the components, sub-assemblies and parts needed to build a product. Also known as an assembly component list or production recipe, BOMs are essential for many manufacturing and supply chain processes such as planning, purchasing, inventory and scheduling.
Different functions within a company use different types of BOMs including engineering, design and operations. The most common type of BOM is the manufacturing bill of materials.
Definition
A bill of materials is a list of raw materials and parts required to assemble and manufacture a finished product. It provides a structure for bringing new products into production and helps ensure repeatability in assembly processes.
BOMs are a critical component of a manufacturing company’s supply chain and can provide valuable insight into supply chain costs, inventory management and other factors that affect profitability. Regardless of whether a company manufactures its own products or outsources production, an accurate, comprehensive and regularly reviewed bill of materials is a crucial tool for success.
Companies use two types of bills of material: an engineering bill of materials (EBOM) and a manufacturing bill of materials (MBOM). An EBOM is used during the design stage and lists all parts, components, and materials that are needed to produce the final product. During the development stage, an EBOM can be used to identify potential issues or changes in a product’s design before it goes into production mode.
A BOM can be formatted in many different ways depending on the product being manufactured. It may include part names, quantities and descriptions or it can be presented in a graphical format. Typically, a BOM will contain the item number, quantity and cost of each component. It should also provide the location where the component can be obtained or manufactured, along with any specific instructions that are needed for assembling or building the final product.
Purpose
As a crucial part of the product development process, the bill of materials pulls together all sorts of information. It is important for companies to have accurate and consistent BOMs so that they can accurately track inventory and avoid costly production delays due to a lack of resources. A company can also use a BOM to identify wasteful spending, make more informed purchasing decisions and stay ahead of potential materials shortages and other supply chain disruptions.
A company may need to prepare different types of BOMs depending on the type of project it is working on. For example, engineers overseeing a project will often create engineering bills of materials (EBOMs). These bills of materials display the assemblies and parts designed by the engineering team based on a computer-aided design or CAD drawing. On the other hand, manufacturing teams will rely on a manufacturing bill of materials (MBOM). These bills of materials display the components and sub-assemblies required to produce a finished product.
Regardless of the level of complexity in a BOM, it is important to ensure that it has the following components:
Format
A manufacturing bill of materials identifies all the raw materials, subassemblies and components needed to make a single finished product. It also lists the quantity of each item needed. This information is critical for manufacturers, as it enables them to track inventory and ensure that the proper quantities of each part are in-house when needed. It also helps minimize production delays and waste.
A BOM can be a spreadsheet or a table, and it may include columns for part number, description and cost. It can also contain images to help identify each component and its role in the product. Ideally, the BOM is updated regularly to account for changes to regulations or industry standards that affect certain materials. It should be viewed by a cross-section of the company, including engineering, purchasing and material management departments.
There are several different types of BOMs, and the choice depends on what type of manufacturing process is used. An EBOM (engineering bill of materials) is used during the design stage, while an MBOM (manufacturing bill of materials) is used in the manufacturing phase to produce the final shippable product.
A multi-level bill of materials displays the parent-child relationship between a component, a sub-assembly and an assembly. This format is often referred to as an indented BOM, and it’s more common for more complex manufactured products.
Variations
The exact format for a BOM can vary depending on the product type, manufacturing process and other factors. Generally, BOMs are displayed in a hierarchical format with the top level displaying the finished product and each subsequent level showing individual components or parts. Typically, each part or component in the BOM includes a number, description, unit of measure and cost. Other information that may be included in a BOM includes an identifier, procurement method and vendor name.
A bill of materials contains all the raw materials, components and assemblies that are required to construct or manufacture a final product. It can also contain a detailed list of assembly processes and a description of the product. This information is used by engineers and suppliers to plan inventory, purchase supplies and track the status of work in progress. BOMs can also be used to generate invoices, monitor production and identify errors.
There are different types of BOMs, including engineering bills of materials (EBOM) and manufacturing bills of materials (MBOM). An EBOM is created during the design process and often includes alternative and substitute part numbers and drawing notes. A MBOM is used during the manufacturing process to record and store the details of how a product will be assembled, including detailed instructions and routes. BOMs can also include the product code and specifications, which allows them to be compared to other products.