An engineering BoM, also called an engineering bill of materials, specifies how a finished electronics project is designed. It is a standardized and centralized source of information that guides electronics manufacture. In its simplest form, it can be a single table of materials with their associated costs and other relevant data.
Its construction is often aided by CAD design and may include suggestions for substitute parts if desired parts are not available. A finished electronics project may include more than one engineering BoM. Well-constructed engineering BoMs streamline many business processes, including cost monitoring, requirements planning, inventory management, and record-keeping.
How is an Engineering BoM Structured?
An engineering BoM is a hierarchical document that starts with the finished project, then continues into more specific parts and descriptions. These documents come in two types: single-level and multi-level. A single-level BoM is usually a list of components where repetitive elements like assemblies and subassemblies only appear once. A multi-level BoM is suitable for more complex projects because it describes specific relationships between different parts and assemblies within a project. There may be some repetition within a multi-level BoM for the sake of clarity. Multi-level BoMs may also be depicted as hierarchical charts to show relationships at a glance. These hierarchical charts do not contain all the necessary information for a complete BoM, however, and are instead used as helpful additional references.
Since there may be multiple engineering BoMs related to the same project, and the complexity of project parts may vary, a single project may contain both single-level and multi-level BoMs. A large BoM may encapsulate multiple smaller BoMs, depending on organization preferences. BoMs can also change dramatically between revisions, and it is common to keep previous BoM versions on file for reference.
Although an engineering BoM describes the relationships between components and assemblies, it does not specify which parts are needed at various stages of production, or which packing or shipping materials are needed. These requirements are placed in a manufacturing BoM. A manufacturing BoM may be linked to an engineering BoM in some way within an organization, but they are different documents with distinct purposes. Combining these documents, without careful organization, could result in production delays or shipping errors.
A clearly structured engineering BoM streamlines many essential processes in the life cycle of an electronics project. After an electronics project is manufactured and shipped, the engineering BoM helps designers and engineers to address any issues that may arise. The clear structure, alternative parts, and previous revisions contained in an engineering BoM eliminate the need for a lot of costly testing and diagnostics work, allowing manufacturers to create an improved product much more quickly.
A Simple Multi-Level BoM Hierarchical Chart for a Bicycle.
How is an Engineering BoM Maintained?
Successful and efficient maintenance of an engineering BoM requires the proper software and internal processes within an electronics organization. While the software used to organize and update a BoM may vary, similar BoM maintenance processes are useful in almost every electronics manufacturing context.
It may be possible to maintain a single-level BoM with a simple spreadsheet or word processing document. While it may be tempting to use complex software for even the simplest BoMs, it’s important not to overcomplicate the process by which a BoM is created. Overcomplicating a BoM process can lead to errors in finished BoMs that are difficult to find or correct. Designers should always remember that the goal of an engineering BoM is to create a clear structure with easily accessible data, not to be dependent on a specific piece of software in all contexts, regardless of its utility.
The key to BoM processes is communication. Within a BoM team, everyone must clearly understand their role and be able to quickly collaborate on any new information. It’s a BoM team’s job to communicate requirements in a clear way, so a breakdown in communication can lead to flaws in a finished BoM. BoM processes should include frequent information integrity checks, rounds of revision, and collaborations with test readers, where possible. An engineering BoM is a technical document that must be understandable by people with many specialties, so ensuring readability and precision is essential. BoM maintenance processes should prioritize the correct and efficient transfer of information at all times.
Where Can Designers Learn More?
Ultra Librarian provides quality CAD software to help designers make reliable engineering BoMs. We also have partnerships with many reputable electronics vendors, including Texas Instruments, Maxim, Toshiba, and TE Connectivity. Ultra Librarian strives to take the busy work out of creating complex BoMs so manufacturers can quickly create quality electronics. Working with Ultra Librarian allows you to receive all the benefits of reliable CAD software that makes it easy to create complex designs. Register today for free!