I’ve been trying to increase the repeatability of the machine by doing away with the paper/calibration card method. I bought a cheap Z-probe off Amazon that was designed for the chinese 3018 machines for a few bucks and crimped some alligator clips to the ends instead of the standard dupont connectors. My probe measures at exactly 19.3mm with calipers consistently around with several measurements.
Sadly since there’s no auto-probe routine, this is the method I use;
1: Get a cheap multimeter and set it in continuity mode.
2: Clip the wires to the probes of the multimeter, ensuring they do not touch.
3: Place the Z-probe base on the material (or spoilboard using my method above when changing bits)
4: Clip the shielded alligator clip to the bit.
5: Follow the ‘calibration card method’ by jogging down until using 0.1mm increments.
6: The multimeter beeps, signaling continuity, and thus the bit touching the probe.
7: Jog up 1mm, remove the probe/clip, jog back down the 1mm, then jog down what the probe measures (i.e. 19.3mm that my base measures)
8: Set Z origin.
This is a bit more fiddly than it being automated on say a 3018 machine, but it’s a lot more accurate than moving the card back and forth (plus you’re not off by the thickness of the card). This was the results of my first test using this method. Roughing was done with a 3.175 flat end mill, finishing was done with a 0.25 radius tapered ball, in 6x6x0.75" solid maple.
