Printing Jigs
While I was waiting for drill bits, I decided to solve a problem that’s been bothering me for a while. The frame (made of 2020 aluminum extrusions) is slightly out of square. It wobbles when I place it on a flat surface, such as a granite countertop. This has been nagging at me because, in my experience, the extrusions are cut very precisely. Mechanical precision is important when you’re trying to get a robot not just to balance, but to balance well.
After a lot of thinking and tweaking, I came to the conclusion that I am the problem. To hold the extrusions together, I tapped the end holes with an M5 tap. That’s a good idea, except I did it too hastily—the threads were not quite straight. When you add up all the minor misalignments, you end up with a wobbly frame.
To fix this, I started over using some cast corner brackets I found on Amazon. I also decided to tap some holes in new extrusions for non-structural parts to be added later. This time, I printed jigs to keep the threads straight. I also printed another jig to drill access holes in the corner brackets.
