How NOT to Design for Manufacture
There are many articles, and blogs, out there telling you everything you need to do to be a great designer. I have come to the conclusion that these are either incomplete, inadequate to solve the problems of design, or they are not reaching the legion of designers and draftspersons who cannot read. Therefore I have put together this blog series to explain how NOT to design. Hopefully, through its subtle humor, it will be able to reach the hopelessly backwards. Don’t be offended by the label, if you are hopelessly backward in all likelihood you don’t know that you are. If you at any point find yourself getting huffy puffy about a particular portion of this series don’t worry, there’s hope for you yet and you are merely backwards.
- Do not learn anything about how mills, lathes, presses, or any of that other stuff works. You’ll never be running one so it doesn’t affect how you do your job.
- Similarly don’t bother learning about those coatings you’ve been applying by rote, I mean how thick could they be anyway.
- Never worry about inspection when dimensioning. Inspection isn’t very hard now that we have CMMs, they’ll figure out how to measure it.
- GD&T is for designers who wish they were engineers. Even so, it can also be used in an obscure fashion to conceal your lack of GD&T knowledge and make you seem superior to your peers.
- When it comes to tolerancing, tighter is always better. If they can’t make it we need a new machine shop.
- Nonconformance in production means the machinist is dim, or lazy, or both. It couldn't possibly have anything to do with you or your design.
- Always deny manufacturing changes, after all what do they know about making this stuff.
- If they are very persistent, immediately give them what they want so they will shut up.
- Supply chain is the technical expert to handle all aspects of the manufacturing of your part. They attend omnipotence classes and should be worshipped.
- Consulting manufacturing in the early phases of a job is just a waste of time.
- Switching vendors constantly on the basis of price is the key to reliability and repeatability.
- If you can model it they can build it.
- The shop doesn’t need to make money on this part; they’re getting you everywhere else anyway. This also goes for everywhere else.
- Assembly is not an option.
- Disassembly is unnecessary. You designed it perfectly, remember?
- If you can reach the groove, the O-ring will fit easily.
- What’s a little interference between friends?
- Contrary to popular belief gun drilled holes can be held to tolerances of up to six decimal places over a twenty foot length. It's cheap too!
- The best way to apply manufacturing datums is at random. It keeps those guys on their toes.
- It is best to create 20 page manufacturing drawings for the simpletons in manufacturing. It isn’t confusing at all.
- Never go out into the shop and assemble your tools, you might get dirty. Besides what could you learn from grease anyway?
- If it doesn’t fit, you need a bigger hammer. (Author’s Note: Before the nasty-grams come rolling in I will admit sometimes you do need a bigger hammer. More often than not, however, you are just a dummy.)
Now you know how NOT to apply DFM to your tools. I know we already had a ton of knowledge in how not to do this, but I hope this encourages us to stay away from some of the more egregious of these failures. Please post your own how NOT to DFM suggestions here as well.