Bill of Materials (BOM): What is it and How to Create one

The manufacturing industry is behind many product development projects, which play a crucial role in the economy. If you oversee such processes, your attention to detail and ability to efficiently document your practices will determine the success of your project. You will need to capture all the critical information involved in production to make your product design a reality. You can do this through a detailed and accurate bill of materials.

A bill of materials is one of the key elements of a successful product development process. If you are embarking on a project, read on to find out what it is and how to create it.

What Is a Bill of Materials (BOM)?

A bill of materials (BOM) is a detailed record of the components, raw materials, and processes involved in manufacturing, constructing, or repairing a product or service. It is usually formatted in a hierarchy-style draft where the highest level represents the finished product or service, and the lowest level describes the raw materials and components.

If the product or service being produced is an engineering component, the bill of materials will differ from that used in an assembly process.

How Bill of Materials (BOM) Works?

A bill of materials (BOM) is a report that outlines all the information involved in manufacturing a product. It lists all the raw materials required for the process and explains the instructions for assembly. Generally, this document marks the beginning of the assembly process in manufacturing in fields such as design, engineering, manufacturing, and operations.

Because a BOM captures all the materials needed for the assembly process, including their dimensions and quantities, it ensures that these parts are ready and available during the appropriate stages. This allows for a streamlined process. Generally, the BOM will list these items by:

  • Part name
  • Part number
  • Quantities
  • Unit of measurement

If the person preparing the BOM makes a mistake, it could delay the entire production process as the team involved works to find the raw materials and re-define the assembly process. This can mean hefty operating losses for the company.

Before Creating a Bill of Materials

  • Record the Consumables. Consumables are items you use during production that are not part of the final design, such as wires, glue, and fasteners. You must keep track of these items and include them in the acquisition part of your BOM; else, you won’t have them when assembly begins.
  • Prepare Supporting Documents. You will use documentation that is part of the assembly process but cannot be recorded in the BOM in its entirety. This includes documents like datasheets and CAD drawings. During production, you should maintain these documents and record them in the BOM.
  • Record all the Relevant Data. Your BOM should include all the information related to the assembly process, no matter how minute. It should be detailed enough that anyone who was not a part of the production can understand the data process without consulting you.
  • Keep Track of all Changes. Before the final stage of production, you will likely change your BOM several times, creating multiple versions. Therefore, it is vital that you keep track of and distinguish all the versions, so anyone who interacts with the BOM acquires the correct document.

Essential Elements of an Effective Bill of Materials

When prepared correctly, a Bill of Materials (BOM) should help your build, produce, or manufacture a product or service correctly. It must contain the following key details to help you achieve this:

  • Part Name — Indicate the name of each part so you can easily identify them.
  • Part Number — Give every part a unique identifying number that you can use to reference them in the rest of the BOM. Your numbering scheme can be intelligent or non-intelligent.
  • BOM Level — As mentioned, the BOM is structured as a hierarchy. This number indicates the level at which the part falls on the hierarchy so readers can understand the structure.
  • Part Description — Describe each part in detail so you and other readers can identify them easily and differentiate them from similar components.
  • Quantity — For each assembly, indicate the number of parts required. This record will help you make acquisitions and purchases.
  • Procurement Type — Explain how each part in the process is to be made or purchased. Should it be customized or bought off the shelf?
  • Unit of Measurement — State the measurement classifications for each of the parts to be made, purchased, or used during assembly. Examples of measures you might use include feet, inches, and ounces.
  • Reference Designators — For products that contain a printed circuit board assembly (PCBA), indicate the reference designators for where each part goes on the board.
  • Stage/Phase — Indicate the phase at which a part is in its lifecycle. For example, if the part has not been approved, you can tag it as ‘in design’ or ‘unreleased.’
  • BOM Notes — This section allows you to note down any relevant information you think BOM readers should know to understand a part, stage, or process.

Types of BOM

  • BOM List. The BOM list is often used during the initial stages of the production process to order replacement parts in preparation for possible errors. It allows the person in charge to make acquisition orders for the necessary parts. Generally, a BOM list can be a manufacturing BOM or an engineering BOM.
  • Manufacturing BOM. A manufacturing BOM highlights all the parts and processes necessary to assemble the product. It also facilitates the shipping of the product to the consumer by outlining the packaging details (materials and logistics). Overall, it is where you can find information about the manufacturing process and product execution plan.
  • Engineering BOM. An engineering BOM highlights the final design of the finished product and any alternative parts described in the notes. As a summary of the completed process, it highlights the product name, product code, part name, part number, descriptions, quantity, and dimensions, among other primary details.

Key Points

A Bill of Materials (BOM) is a detailed source of all the information involved in manufacturing a product or service. It highlights all the raw materials required and explains the manufacturing process that must be followed to produce the final design. When creating a BOM, you will use a hierarchical format where the top lists the finished design and the bottom contains the individual raw materials and components. This document is crucial to production in several fields, and any mistakes in it can lead to hefty losses.

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