Monday, August 15, 2016

When in Doubt, Build a Jig

When trying to machine or manufacture something, building a jig to hold something in position is almost always a good idea. I have been struggling with how to improve the accuracy of position of a piece of acetal inside a piece of square aluminum tube. The problem is that the acetal sometimes ends up a fraction of an inch too far out or too far in. So I took a piece of acetal already at the right depth and angle in an aluminum tube and put that against the workpiece in a vise.  Then I use a smaller piece of aluminum tube behind the acetal to tap it against the opposing jig.  It is then exactly in position.  Because the aluminum tube into which the acetal goes has a 1/4"-20 hole in it, a thumbscrew locks the smaller aluminium tube in position against the rear of the acetal piece. Now I can drill through the square aluminum tube into the acetal and be sure that it is exactly matched up with the end of the aluminum tube where it meets the jig.

1 comment:

Will said...

When I first started working in high tech/Silicon Valley, I was surprised at how often I discovered that there were no real jigs or other types of special tooling for the low volume manufacturing areas. If you want consistency, and want to lessen the requirement of depending on the variable talent found on the production floor, you have to put some effort into tooling that will enhance the ability to make a predictable assembly.

I ended up specializing in that sort of thing, to some extent. Tooling and fixtures, and re-designing parts and assemblies to be easier to build, and work better. The R&D engineering groups usually ended up hating me, because I made them look bad. Partly that was due to them not being willing to work with me on my ideas, so they had no ownership when it got to higher levels. Really stupid lack of thinking on their part. All ego, no logic. Idiots. I would have been happy to collaborate with them, but since I didn't have the sheepskin, and rarely the appropriate title, they felt that it was ok to defend their "turf". The fact that it was costing the company lots of money never seemed to bother them.
The fact that I was a better mechanical designer than any of them was evident, so they retreated to the Not Invented Here position. Ran into that in nearly all the companies.