A Bill Of Materials (BOM), which serves as the foundation for building the product. It’s a fundamental set of data, used throughout the process. A well constructed BOM clearly communicates all of the technical ingredients required to build the product.
Because the bill of materials pulls together all sorts of product information, it is common that several disciplines (design and engineering, document control, operations, manufacturing, purchasing, contract manufacturers and more) will consume data contained within the BOM record to get the job done right. In fact, engineers and manufactures rely so heavily on BOMs they their own special subsets called the engineering bill or materials (EBOM) and the manufacturing bill of materials (MBOM). The BOM guides positive results from business activities like parts sourcing, outsourcing and manufacturing, so it is important to create a BOM that is well organized, correct and up-to-date.
What to include in an effective bill of materials?
An effective BOM doesn’t have to be generated by sophisticated software — it can be as simple as an Excel spreadsheet.
BOMs are usually broken up into several categories.
Categorization makes it easy for you, your colleagues, and vendors to find what they need in your BOM. For example, the PCBA (printed circuit board assembly) manufacturer only cares about the PCBs and the components that need to be surface mounted onto the boards — the packaging components usually don’t need to be procured for the early proto-builds.
Because one of the main functions of the BOM is to ensure that the product is built right, it is best to include specific pieces of product data in the BOM record. Whether you are creating your first bill of materials or are looking for ways to improve how you create a bill of materials, here is a high level list of information to include in your BOM record:
BOM Level—Assign each part or assembly a number to detail where it fits in the hierarchy of the BOM. This allows anyone with an understanding of the BOM structure to quickly decipher the BOM.
Part Number—Assign a part number to each part or assembly in order to reference and identify parts quickly. It is common for manufacturers to choose either an intelligent or non-intelligent part numbering scheme. Whichever scheme you use, make sure you avoid creating multiple part numbers for the same part.
Part Name—Record the unique name of each part or assembly. This will help you identify parts more easily.
Phase—Record what stage each part is at in its lifecycle. For parts in production, it is common to use a term like ‘In Production’ to indicate the stage of the part. New parts that have not yet been approved can be classified as ‘Unreleased’ or ‘In Design’. This is helpful during new product introduction (NPI) because it allows you to easily track progress and create realistic project timelines.
Description—Provide a detailed description of each part that will help you and others distinguish between similar parts and identify specific parts more easily.
Quantity—Record the number of parts to be used in each assembly or subassembly to help guide purchasing and manufacturing decisions and activities.
Unit of Measure—Classify the measurement in which a part will be used or purchased. It is common to use ‘each’, but standard measures like inches, feet, ounces and drops are also suitable classifications. Be consistent across all similar part types because the information will help make sure the right quantities are procured and delivered to the production line.
Procurement Type—Document how each part is purchased or made (i.e. off-the-shelf or made-to-specification) to create efficiencies in manufacturing, planning and procurement activities.
Reference Designators—If your product contains printed circuit board assemblies (PCBAs), you should include reference designators that detail where the part fits on the board in your BOM. Capturing this information in the BOM can save time and help you avoid confusion down the road.
BOM Notes—Capture other relevant notes to keep everyone who interacts with your BOM on the same page.
Documenting all this information in your BOM will keep business activities and manufacturing tasks on target.