Setting only Z via BitZero gives incorrect height

[Etoimos (Keith)]

I recently made and L fence for my table and ran into an issue where every time I tried cutting something, the first pass was always 2-3mm too deep and it would cash the machine. After extensive troubleshooting, I was able to determine that if I put the BitZero on my stock and simply use the built in Z only Probe function, the CNC would always think my Z was several mm lower than it just probed to. If I use the XYZ probe function with the BitZero, it gets the height correct every time. I can reproduce the issue at will.

Is there a special way to use the BitZero when only setting the Z? Right now I am moving the bit a couple of mm above the BitZero and running the Z only Probe function. It completes the probe process with no errors and looks just like the Z portion of the XYZ Probe function.

Any thoughts on this?

[WillAdams (William Adams (Carbide 3D))]

When probing for Z, the BitZero should be fully on the surface, see:

Using/verifying the BitZero

Here is how I check out the functionality of the machine/BitZero: first check that you have sent the correct Z-axis configuration This can be easily done by jogging down to the wasteboard surface, setting zero, then using the Rapid Position command to lift 6mm above the current zero — measure how much the machine moved — if it’s wrong: open the Log Window go to the MDI (EDIT: Note that it will need to be enabled in options in current versions) and send $$ and check that the Z-axis steps/mm …

[Etoimos (Keith)]

Thanks for the link Will. I was totally using the BitZero incorrectly for setting only the Z. I was still hooking it onto the corner of the stock. This of course through off the reading.