After a lot of preperation the mini-mill is cutting foam again! Pic shows a little test cut from semi hand-rolled G-code. It was done with a 3.2mm ball-nose endmill, using a 2mm stepover and running at ~ 400mm/minute feed rate.
Frankly, the biggest thing it showed was that I feel the need for speed! It could easily have cut at > 1000mm/minute given the fairly shallow cuts being taken. My steppers are pretty tiny, and the threaded rod I'm using is only a 1.25mm pitch so it's spinning pretty fast to reach the 600mm/min rapids it's currently doing. I think I see a purchase of some ACME threaded rod in my future... Which will mean re-doing all the delrin nuts again, dammit.
Currently debating if I should buy 1/2inch or 5/8th inch rod (~12mm and ~16mm respectively). The 12mm is 2.54mm pitch, and the 16mm is 4.3mm pitch, so the 5/8th is capable of much higher speeds, at the cost of some accuracy and backlash. Still very undecided on this.
I say 'semi hand-rolled' G-code as it involved initially a significant chunk of perl, and eventually a chunk of C code that properly compensated for the cutter size. At the moment, it will take a PGM image and convert it into G-code, treating the grey levels as a high map. It's did a semi-reasonable job of carving a picture of K into foam; albeit with some oddities given the simple lightlevel->height conversion. Took nearly an hour to carve a 120mm x 80mm image tho. I am seriously feeling the need for speed!
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