I did some real 3D routing today!
First up, I did the backlash tests correctly (using just a single movement) and discovered 2thou of backlash on the X-axis only. The other axes didn't have any measurable backlash so I left them as is.
Rhino has been purchased but for some strange reason they don't let you download. So I had to pay 15 bucks to get it posted and now have to wait...
And now for the good stuff. Here's the 3D model drawn in Rhino (with identifying marks censored):
And here's the result cut in high density insulation foam (left over from making terrain). The part is 100x120mm:
Obviously the finish is pretty ordinary, but I didn't want to have it take three days to machine! Initial roughing was done with a big 5mm endmill, with detailing done with a 2mm ball ended cutter. It took about 1.5 hours to machine. Considering the relatively coarse final pass, the result is quite acceptable for the purposes of demonstrating to the client what I want them to spend a lot of money on tooling for! Obviously running with a much smaller cutter and closer passes could give a very nice result, at the cost of much longer machining time.
For the record too, USB CNC hasn't missed a beat thus far!
Oh and I found a new program for toolpath creation: . It's WAY faster than PyCAM (it took about 5 minutes to do what took PyCAM 1 hour!) and have given much more consistent, correct results. And it's still free!