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Bill of Materials (BOMs) 101

This blog post may be a little less exciting than the last two; but it’s essential!  Today I’m going to talk about Bills of Material(s), more commonly known as BOMs.  

What is a BOM?

At its simplest, a BOM is a list of all the parts in an assembly.  It documents Important information with each part, such as: part number, description, vendor, quantity used, cost per part, etc.  There are thousands of potential attributes you could list. BOMs can be as simple or as complex as you want. They serve the essential function of letting engineers and assemblers keep track of all the parts and where to look for more information about them.  If you look at the very beginning of Ikea instructions they have a list of parts, how many are included, and a label number. They call it a parts list, but it’s really a BOM. 


Get the Dragon Standard BOM Template


When Should You Create Your BOM?

A BOM might not be that useful, when you are in the phase where you are building prototypes to test out different ideas.  In this phase assemblies are changing rapidly as different ideas are tested.  Whole parts or even sub-assemblies might be thrown out as ideas fail, and early parts may be made in-house, or by a completely different vendor than the one for a finished product.  

You need to make a BOM, once you move to the phase where you are building prototypes to refine the design.  In this phase changes are less dramatic; you likely will be adjusting part geometries, rather than creating completely new parts.  

For larger projects, either with more parts or more engineers, you may want to think about using a BOM earlier.  With more complexity, tracking everything becomes harder so writing down information is more important.

Keep all BOM information straight and you’re fine, get it wrong and you will have chaos!

BOM Tools

A typical tool for creating a BOM is a spreadsheet.  Traditionally this has meant Excel, more recently - Google sheets, Office 365, or other web based spreadsheet systems.  The advantage of real time web based systems (not files saved to a shared folder) is you can be certain everyone is looking at the same version of the document.  This becomes your one source of truth.  Sharing traditional files can result in some people having old files and wasting time working with outdated information, which has been and continues to be a challenge.

There are numerous BOM templates available online - including one from Dragon innovation - that you can easily download and customize to work for your project.  There is also purpose built BOM software. I have never been involved in a project where the features were worth the extra cost and setup, but as teams grow and assembly complexity increases, the special features of these systems become more useful and worth the cost.

A brief introduction:

I'm James Berg. I like making things, I do it professionally and I do it in my free time. Currently I work at Athos, a smart fitness garment company; previously I have worked in consumer electronics and solar power.  In my free time I make things ranging from modular shelving to displays that tell me when the next bus is stopping near my house to gingerbread carousels. You can follow me on Twitter here: 

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