So not having a very successful time on Nathan's X-Carve.
Auto-Level works excellently. I added an inline 2pin connector to the Dewalt 660, so I can unplug it at the spindle whenever I need to (currently it runs to an E-Stop, but the E-Stop also turns the supply for the grbl off too). Cleary makes a difference vs. before.
Auto-Leveled code seems to be too accurate? As it cuts, it seems to get lower and lower. I tested one at a cut depth of 0, and halfway through, it was easily cutting through the copper. Not sure if it could possibly be a round error build up on the machine from the auto-level code. Could possibly be heat build-up on the bit* . Tried removing the jumper on the grbl, re-programmed it for a higher step count (and hopefully reduce rounding errors) but it didnt seem to have too big of an effect.
Dewalt 660 Spindle seems to have a pretty large runout. Tried using 0.3 tool diameter, still obliterated traces.
Going to remove the quiet cut spindle from my router and temp. install it on Nathans X-Carve, since it seems to have less runout. It also doesn't get anywhere near as hot as the Dewalt does (which has to cool down before touching the bit due to how hot the motor itself runs, even mentions that in manual).
Bottom Right is with a cut depth of 0 . Partway through it suddenly starts cutting through, vs. before where it wasn't hardly touching.
Views of progressively larger bit diameters. Started at .15mm, .2mm, .3mm , bottom up.
*The bit should be Tungsten Carbide, which has a thermal expansion coefficient of 5.5um/mC.
If the bit is 1.5" long, or ~40mm, at room temperature (25C), then the bit on the dewalt, which was hot enough to jerk my hand away, was say 100C, then:
dl= 0.04 + 0.04*0.0000055*(100-25) = .0400165m = 40.0165mm
This means the bit has increased in length by .0165mm. Considering the thickness of the 1oz copper is only .035mm, if your cut depth was originally .04, then with the thermal expansion you are now cutting .0565, significantly more then before the bit heated up.
This shows that keeping your bit cool is extremely important, and not just for overall bit life. It may be necessary to use the quiet cut spindle, which with all metal case and lower power keep it cooler, and properly lubricate the board.
Is the math right or did I mess up a decimal?