What is a Bill of Materials | Understand Bill of Materials
What is a Bill of Materials | Understand Bill of Materials


Date: 23 Sep 2022

What is the Bill of Materials?

A complete inventory of materials, assemblies, subassemblies, parts, components, and each manufactured product is contained in the bill of materials (BOM). It also includes instructions on how to procure the materials and how to use them. BOM is referred to as product structure, assembly component list or production recipe. The usual format is hierarchical, with the top level showing the finished goods and the bottom level displaying the various parts and materials.


What Are the Advantages Of Using a Bill Of Materials?

Companies that adopt lean production techniques based on continuous improvement can benefit from BOMs. Manufacturing is made precise and effective by the bill of materials. Some of the benefits of BOM are listed below.

  • Plan your raw material purchases.

  • Track and plan material requirements

  • You can know the estimated material cost

  • Manage inventory

  • With the help of BOM, you can stay alert to material shortages, expediting charges, and planned and unplanned downtime. 

  • Beneficial in controlling a budget

  • Stay on schedule

  • Maintain records

  • Reduce Waste

  • It helps in identifying the cause of product failure.

  • It helps in identifying the faulty component. 

  • You can find a vulnerability in the software components.

  • It can help in improving supply chain security.


Who Uses Bill Of Mateials (BOM)?

Every manufacturer creating products for any industry started their manufacturing process by creating a bill of materials for the specific product. For example, the engineering department creates an engineering bill of materials (MBOMS). The following teams use the Bill of Materials.

  • Material procurement team or sourcing materials. 

  • Manufacturing or production team or department, including contact manufacturing partners, design, engineering and mechanical teams. 

  • Assembly team or department

  • Operations Team


Structure Of Bills Of Material

The two types of BOM representation that are most frequently used are single-level and multilevel BOMs.

  • Single Level BOM -This is a simple list that includes the quantity needed for each assembly or subassembly for the product that is being displayed. It is simple to create this bill of materials. However, this BOM is not appropriate for complicated products because it doesn't define the relationship between assemblies and sub-assemblies. A single-level BOM makes it challenging to identify the defective element when a new product fails.


  • Multilevel Bills Of Materials - The creation of this BOM requires more labour, but it provides more information, particularly on the parent and child parts of the product. A multilayer BOM's product structure demonstrates the connections between assemblies and sub-assemblies and parent and child items.


Content Of Bills Of Material (BOM)

Bills Of material contain the detail of the particular product's engineering, design, document management, manufacturing, purchasing, contract manufacturers, etc. Below is the list of particulars in a typical bill of materials. 

  • BOM Level - It signifies a level identification number depicting each part or assembly to fit in the hierarchy of the BOM for a quick understanding of the BOM structure. 

  • Part Number - It is assigned to each part or assembly for reference and identification. 

  • Pat Name - It records a unique name for each part or assembly.

  • Phase - Records the stage that every part and product is along its lifecycle.

  • Description - Provides a detailed description of each part to distinguish between similar parts and conveniently recognise specific parts.

  • Quantity - Records the quantum of parts for each assembly or subassembly.

  • Unit Of Measurement - Categorises the measurement in which a part is used or purchased, for example, inches and feet. 

  • Procurement Type - How to purchase each part along with its off-the-shelf or made-to-specification.

  • Reference Designators - They are used in the case of the printed circuit board assemblies (PCBAs) to explain where the part fits on the boa in the BOM.

  • BOM Notes - It captures other important notes for everyone's understanding and clarity about the BOM and product. For example, a list of alternate suppliers. 


Types Of Bills Of Material

The BOM combines all the information that goes into building a final product. There are three main types of bills of material. 

  • Manufacturing - A manufacturing bill of materials (MBOM) contains a thorough list of every component and subassembly required to make produced, shippable finished goods. A product's many components are explained in relation to one another by the MBOM, as well as information on the pieces that need to be processed before assembly. 

  • Engineering - A bill of materials for engineering (EBOM) lists the assemblies and components that the engineering department has created. The EBOM is a mechanical or technical product diagram showing the component structure from a functional perspective.

  • Sales - Before the product is assembled during the sales stage, the specifics are described in a sales bill of material (SBOM). The list of completed goods and the materials needed to make them must appear separately in the sales order documents in an SBOM. Instead of being maintained as an inventory item, the final product is controlled as a sales product.

Other types of BOMs include the following:

  • Configurable BOMS - They are used in industries with multiple options and highly configurable products. Configurable bills of material are designed to meet unique customer specifications and identity building materials, labelling, and packaging materials. 

  • Production BOMs - It is a structured list of all components and subassemblies used to produce a parent item. It is the basis of the production order.  

  • Assembly BOMS - They list the parents as a sales item rather than an inventory item.

  • Software BOMS - They list the components of a piece of software which may consist of a mix of commercial and open source products. SBOMS enable developers to ensure disparate software components work together, are up to date and are protected from vulnerabilities. 


How To Ensure An Effective Bill Of Material Management? 

To ensure that the production process is as efficient as possible, a custom manufacturer must include all relevant information in the BOM. After several iterations and involving numerous teams, a final bill of material is produced. While utilising a spreadsheet to construct a BOM is one option, the optimal method for managing BOMs is to use an enterprise resource planning (ERP) system. BOM needs constant observation throughout its whole existence. As a result, many evaluations and modifications are needed to produce high-quality output.