Week Twelve: Machine Design

This week, we were supposed to build the MTM Snap Machine and work on our final projects. I was out of town Wednesday through Sunday for interviews in California, so the only MTM session I was able to make was on Tuesday night where we talked about how to cut out the dxf files on the Shopbot. Pretty unexciting, so in spirit of machine design week I did a rough pass at the design of my final project (CNC hot wire cutter).

I plan on having 2 stepper motors drive the 4 stages via timing belts. The drive mechanism is mostly based off of Ilan Moyer's Fab-in-a-box machine, and I plan on talking with him about some questions I had about it. I also plan on lasercutting most of these pieces so I can make them fairly quickly.

I also did some work on the electronics side of my final project. I ended up switching to using high-side drivers after my other board decided to switch at 7 Hz, which I had trouble debugging. New board's buck works, with one caveat -- it seems unstable when given a large load, but if I start it up with a small load and then plug the large load in, it works beautifully. Not sure why it's unstable at startup, given that I'm switching at 200kHz and my LC resonant frequency is 16 kHz, and Matlab told me when I was doing initial calculations that I was far away enough from resonance...