How to Make a BOM
Contents
Simplified Protocol
Hint: A BOM is a Bill of Materials. The critical parts of a BOM are:
- Quantity of part
- Part description
- Link to part. Note that we add multiple links when sourcing is not continuous or reliable.
- Cost of parts
- Total cost
Use D3D_BOM#D3D_v18.10_Bill_of_Materials as a template. Click edit, and make a copy of this to make your own BOM. Or, create a native Wiki template for the BOM to be free of Google Spreadsheets.
Simplified Protocol for a Visual BOM
See example of a visual parts list:
- This is done with Google Slides, making a table, adding links,and adding images cut and pasted from FreeCAD or from suppliers' websites.
Full Protocol
A complete Bill of Materials (BOM) specifies parts/materials/resources needed for a build, and specifies where/how to get them. A formal BOM should include the following for each specified purchase item:
- Item Number
- Quantity
- Item description. Write down unique identifying properties.
- Link - direct link that takes one to arrive at description, source, and price (whenever available)
- AVL - Approved Vendor List - this defines what vendor the item can be purchased from. If a specific Link is provided above, the AVL must also be filled out. This specifies what may be substituted. If it doesn't matter, write Open/Any. If a specific manufacturer is required, write down that specific manufacturer or distributor. The AVL may also be specified in the negative, such as - do not buy from Manufacturer X.
- AVL PN - Approved Vendor List Part Number - specify the manufacturer's or distributor's part number whenever possible.
- MOQ - Specify the Minimum Order Quantity
- Lead Time - time to doorstep - or required from the placement or order to arrival of product at your doorstep. If shipping is not included, specify instructions for how to ship/pick up/deliver the item.
- Price. Critical element for assessing cost to performance ratios of desired products.
- Substitution Notes. A description of what other parts would work - based on general properties, characteristics, criteria, or design rationales being made explicit.
- Other Geographic Sources. Additional entries, corresponding to other geographical locations, may be added on other sheets of the spreadsheet, with the same Item Number. For example, for sources of parts in Chile, a different list of suppliers may be used.
Quality Assessment
To assess the quality of a BOM:
- A BOM is deemed proper when all parts are explicit and unambiguous, where a link is provided to a purchase source. In absence of a link, a supplier phone number or contact information is sufficient.
- Given that a stable supply chain is a common risk in manufacturing, Substitution Notes are a useful feature that would allow a builder to reason what is acceptable as a substitute, and what isn't.
How To
- Create a Google Doc spreadsheet for your BOM - use this BOM Template. Make sure you have included as many of the BOM items in the Introduction above as possible.
- To create a Google Doc from the BOM Template, click the Edit link below the spreadsheet. You will be taken to the actual template.
- Go to File->Make a copy... and make a copy of the template.
- To embed the Google Doc in a wiki page, see Embedding Google Docs in the Wiki.
- If you do not use Google Docs, just use the wiki and create a page with the BOM that includes the spreadsheet by using wiki markup.
- Embed your google doc in a wiki page of your choice. Name the wiki page _______(module) BOM.
- Embed an Editing Link to your Google Doc below the Google Doc on that wiki page.
- Copy the link to your BOM wiki page into the Development Template for your module.
Example
Seminal Reading
Bunnie Huang on a 'proper Bill of Materials' - http://www.bunniestudios.com/blog/?p=2776
- Concepts covered: approved vendor list (AVL), Minimum Order Quantity (MOQ), Lead Time, Cost, Description, Vendor Part Number, etc.
Links
- FreeCAD discussion about BOM - https://forum.freecadweb.org/viewtopic.php?f=8&t=23592
OSE Links
- How to do a Proper BOM
- Product Structure Modeling
