A bill of materials, or BOM, is an essential blueprint for taking a product from design to manufacturing. As it happens, design and manufacturing are controlled by two different, but related, business functions and as a result, two major types of BOMs are used: The Engineering BOM (EBOM) and the Manufacturing BOM (MBOM).
The appropriately named EBOM and MBOM both seek to provide a recipe that a business can follow to make a product a reality for its customer. Purchasing and operations managers rely on the MBOM to make key decisions associated with the manufacture of a product or part and it’s based on the contents of the EBOM, which outlines the product as designed by engineering. Each BOM serves a specific and distinct purpose, yet both are crucial to the management of a product throughout its life cycle.
Bill of Materials: How Different BOMs Impact the Product Life Cycle
EBOMs describe a product based on computer-aided design (CAD) developed by the engineering department. While CAD has a great deal of information and is a great tool, it shouldn’t stand alone as a program’s only BOM. EBOM’s allow each discipline to repackage information from CAD as a comprehensive parts list for its construction. A single component could even have multiple EBOM’s, depending on which department is involved; electrical engineers will usually build different BOMs than mechanical engineers, for example.
How does an EBOM differ from an MBOM? In keeping with the recipe analogy, the EBOM will tell you what you need to bake the cake, but the MBOM tells you how to bake it. If a recipe for cake calls for a single egg at two different steps, the EBOM for that cake likely lists two eggs as a requirement. The same goes for off-the-shelf or modified components contained within multiple sub-assemblies on a manufactured product; the EBOM should indicate how many of each part is needed in total.
Complete and accurate EBOMs are critical for a product’s initial blueprint. The EBOM is handed off directly to manufacturing and the information in it – components, sub-assemblies, materials and tolerances – are used to develop the MBOM and make important decisions on how to source, ship, assemble or modify the listed components into a finished, saleable product.
Any shortcomings of the EBOM can lead to incorrect or incomplete information being used to make important decisions regarding the product. This proves incredibly costly for businesses and renders vital engineering hours wasted. It’s important to remember that without an effective EBOM, there’s no chance for an effective MBOM.
The MBOM is the final blueprint for how a product transforms from its design into a tangible product. While the EBOM focuses on components and materials contained within a design, the MBOM takes that information and repackages it further with more granular detail about components and how they’re related to each other.
No level of detail is too deep for an effective MBOM. The MBOM includes everything that goes into the final product, right down to the marketing material, labels, and instructions that need to ship with the final product. The same goes for consumables such as lubricants used in the process of manufacturing a product. The MBOM also lists the transformational stages of a product, such as an aluminum component requiring a powder coat finish before being bolted onto a final assembly. The component must be listed on the BOM in both its pre- and post-coated form.
The MBOM facilitates the final transformation of a product from a collection of components – both off-the-shelf and custom or manufactured – into a saleable good. This is what makes the MBOM so important to an organization. It’s also used to make most decisions in a manufacturing environment, from operations to purchasing. How a product gets manufactured, where it gets manufactured, and which parts of it are made, bought, or modified are all decided based on the efforts of MBOM development, making this type of BOM critical to success in the new product development cycle.
Understanding the functions of each of these BOM variants and how they relate to each other is key for an organization looking to better manage the life cycle of a product throughout the new product development process.