Bill of Materials

(BOMs... fun with documentation...)

Let's talk about documentation - every engineer's favorite topic, right…? (probably not…)

As a mechanical design engineer, my primary focus is to provide a complete mechanical design package for every project. This generally consists of the following:

- Bill of Materials (also known as, the "BOM")

- 3D CAD Assembly Design Package (Solidworks)

- Component Fabrication Drawings (Solidworks and PDFs)

- Assembly Drawings (Solidworks and PDFs)

It might seem odd that I listed the Bill of Materials first. I really need to come up with a better phrase, but for years I've said, "the project will live and die by the Bill of Materials". The BOM is *extremely important* for the success of a project. Without it, you're largely hoping for the best, wandering lost in the desert of cool ideas that may or may not come to fruition.

The BOM becomes the basic definition of an assembly. Without the BOM, you may forget about that one component that's critical for an assembly or product that has a 6 month lead time. (6 months was considered quick during covid!).

I always start a BOM in Excel. Sometimes the Excel BOM becomes the actual "permanent" BOM for a project. For larger companies, the Excel BOM is fed into more comprehensive / complex software that purchasing departments use for procurement / forecasting, etc. (Things can get complex quickly, but that is necessary for larger companies).

For smaller projects, I may very well actually be the "purchasing department". I'll use the BOM to list the vendor each item was ordered from, maybe expected delivery dates, pricing, etc.

BOMs are great for placeholders during the design phase. I am "that guy" who will occasionally bring up a BOM in a design review. I place items in the BOM that I know are needed, even if they haven't been designed yet. It is often useful to "name names" and place responsible party's names (or group names) in the BOM, etc. When someone says, "Well, I know we'll need a wiring harness for this assembly - we'll get to it when we get to it…" - bam, it goes into the BOM: Wiring Harness, TBD.

I'm not one to get excited about documentation. But I am a *firm* believer in documenting things to a basic level for every project (the list shown above). Anything beyond that helps satisfy regulatory needs, business needs, etc. But I absolutely must have a Bill of Materials to go along with every project.

(My first boss in my engineering life while I was a student intern, Tracy Sherwood, taught me "everything I know" about documentation. We worked at a medical robotics company, where documentation was paramount. I use the fundamentals of what she taught me to this day with great success. Thank you, Tracy!!!)

-James Cuevas, Precision Mechanical Design