@Randy Hey, I don’t believe it’s a machine bug (stepper board thing).
The shapes I’m cutting vary, but they are all basically rectangular blocks. For example, I’ve made a few soft jaws for the vise that sit in the channel, so they’ll be 28.65mm wide (to fit the channel) and then anywhere from 10mm to 50mm long, by 6-12mm tall. When I cut them out of the raw plastic sheets, the base of the cut out rectangle (the part that was stickytaped to the MDF wasteboard) will be basically cut to perfect size but the top part will be slightly smaller along both axes: so if I want to cut out a 15mm x 28.65mm x 12mm rectangular block, the bottom will measure basically perfectly 15mm x 28.65mm, but the top will measure significantly smaller (14.85mm x 28.50mm), for example. The taper is noticeable by naked eye, and definitely noticeable by fit - it will be quite tight to fit in the vise channel but once slotted in will end up loose. There is no melting at all with this stuff - this plastic is super, super easy to machine I think and I end up with perfect little white plastic comma shapes everywhere.
I also milled a small circular peg out of walnut (which was held quite securely by softjaws in the vise) which was supposed to be .125" diameter and only .2" long. I was milling it so that the axis of the peg went along the grain, and when I was done, the diameter of the base of the circular peg was pretty close to .125" but the diameter of the tip of the peg just .2" above that was as small as .119".
@mbellon: It’s a flat carbide .125" 2 flute endmill from Carbide3D. Actually still the one that shipped with the machine. But I haven’t actually used it that much, and only on plastic mostly and a little bit on renshape and wood. A far amount of plywood as well.
A) Stock is Walnut. Or plastic. Feeds and speeds right now are ~.004 IPT, 7500 spindle speed, ~60 IPM, and I’m being quite conservative in stepdown (.01", sometimes I bump up to .04", but doesn’t seem to matter).
B) Yeah, pretty sure collet is all fine. It kind of doesn’t make any sense anyway - collet or endmill placement mistake, or spindle runout - both of those wouldn’t result in a taper with a thin top, right?
C) I’ll see if I can check the endmill - I don’t have a good way to really inspect them, but they haven’t had that much use- some wood and plastic only, and honestly not that much (too busy with my full time work to play with the Nomad too much).
E) If I had bad squaring I’d assume taper only on one side and not the other, right? Like I’d have taper on just the -X wall but not the +X wall, or vice versa?
Anyway, it’s all very confusing to me. Maybe I should slow down my feed/speed and see if that helps…