Back in December, Chumby creator Bunnie Huang wrote an in-depth description of an open source laptop he's been designing. After designing the motherboard and validating all of the other boards and laptop components, Huang would move on to fabrication--getting the circuitry manufactured--and using CNC to cut a plastic and aluminum shell. On Saturday Huang posted a blog titled "The Factory Floor, Part 1 of 4: The Quotation (or, How to Make a BOM)" that delves into the process of getting hardware produced in China. While large-scale manufacturing isn't exactly the same subject, it works as a follow-up to his detailed look at hardware design.
Huang is taking a group of MIT grad students to the factories of Shenzhen to research the manufacturing ecosystem, but the lessons learned there could just as easily apply to Makers looking to produce (relatively) small runs of hardware. "Most Makers trying to scale up quickly realize the only practical path forward is to outsource production," writes Huang. "If only outsourcing were as easy as schematic + cash = product!"
Huang's first lesson for outsourcing: Creating a detailed bill of materials.
"Every single assumption, down to the color of the soldermask, has to be spelled out unambiguously for a third party to faithfully reproduce a design. Missing or incomplete documentation is the lead cause of production delays, defects, and cost overruns."
A bill of materials should include the following:
- Approved manufacturer for each component
- Tolerance, material composition, and voltage spec for passive components
- Package type information for all parts
- Extended part numbers specific to each manufacturer
Huang goes into a ton of detail about all of the requirements, which distinguish a manufacturer-appropriate BOM from one that an engineer could use to build a prototype. It's valuable advice for makers and should be required reading for anyone launching a tech Kickstarter--successful Kickstarter creators often run into trouble coping with the scope of producing thousands and thousands of units.
The Factory Floor will be a four-part weekly series; next week's covers design for manufacturing and test jigs.
(h/t boingboing, photo via ifixit)