I've been trying to get my 3d printed circular knitting machine going for almost 6 months now and I think I'm almost there. I finally realized that it's impossible to crank the heel/toe on this machine - but only because the extra drag of decreases causes it to bind up. It'd totally be possible if the gaps on the spindle were larger so it was less difficult to pull slips/decreases down into it.
Anywho, I gave up on doing everything on the CKM and just cranked a tube (worsted weight - 36 needles) with the intention to do an afterthought everything. I did the heel today. Not great, not terrible, it'll work. I'll try to throw on the toe tomorrow. I definitely should've made it wider so I had a more gradual decrease and a larger heel. But hey - try, fail, learn, do better : )
I did. This was the source model I used : https://www.thingiverse.com/thing:6160954