A few ideas:
- Mill in 75mm spaced holes for those with stock Inventables wasteboard. This could allow for the device to be in the correct orientation and, theoretically, straight with the axis. It would also prevent the piece from moving from the touching.
2a) Using G38.2, you could set your zero point on one side, issue a different G38.2 command to probe the opposite direction. Since you can set the feed rate in the G38.2 command, you can have it go relatively quick and it’ll stop when it senses the touch. Then you can do a short relative move away from the edge and then a slower “double tap” G38.2 for accuracy.
2b) Use a relative move by a safe distance and then issue the G38.2 command. Again, double tap if needed.
Once stopped, you read back the reported position and it gives you the distance traveled. Using the known measured distance with a caliper, you enter in the values in a formula and get your new steps/mm command.
You could also incorporate the Z axis into this. If you make one of your edges you have a little bit thicker, you can probe to the edge in X/Y, back off like 1mm, then probe down to the bottom of the tool. Move back 1mm in X/Y to re-establish contact Then you issue a G38.4 command which moves the Z axis upwards and stops when you lose contact, which again lets you get an accurate idea of distance traveled given a calipered surface.