BitZero V2 Z-Only Probe is 2mm off (?)

I am using BitZero V2 with Carbide Motion build 566 on a Shapeoko HDM. If I do a Z-only probe it sets the Z-0 point 2mm too deep. The interesting thing is that if I do a corner probe, it sets the Z-Zero correctly.

I have played with this quite a bit and the Z-Only probe is consistently 2.0 mm too deep. The Corner probe consistently sets Z-0 correctly.

The BitZero V2 is 13mm thick: 11mm for the aluminum block and 2 mm for the new insulating plastic alignment plate on the bottom. I am willing to bet that BitZero V1 was only the 11mm aluminum block and the Z-Only function was never adjusted for the extra 2mm plastic alignment plate for V2.

If anyone else wants to check this it is easy to do. (And I would appreciate the validation)

  1. Set up some stock.
  2. Put the BitZero V2 on the corner of the stock
  3. Position the probe directly over the aluminum. (Not in the hole like a corner probe)
  4. Do a Z-only probe.
  5. Remove the BitZero.
  6. Do rapid position jog to Z+6mm
  7. Set the Jog rate to 1mm and start doing Z- jogs. You will find the pin hits the stock after 4 jogs.

I found another thread from @jwr that sounded like it might be the same problem but there was no resolution and the thread is now closed.

I have contacted C3D support about this and they keep asking questions about how I am doing it…the implication being that I am not doing it correctly. I am answering their questions but, I am becoming increasingly convinced it is not a user error. I hope they contact the engineers and have them take a look.

I think when doing the z only probe the lip needs to be on top of the surface.
When doing the corner probe the lip is off the surface to reference the edge
The lip thickness is a little over 2 mm (2.2-2.3ish. It’s late and I did a real quick check)

This might be your difference

John

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I have a v1 BitZero and the lip on mine is 3MM. I think the v2 has a thinner rail than the v1. So as John said for a Z only you set the BitZero on top of the work surface and not over the edge. You only put the BitZero over the edge for an X Y and Z probe.

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So I looked at machine coordinates after different probing scenarios. The Machine Z is after hitting the 6 mm above current Z after probing.

Corner Probe
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Z probe but with Bitzero in corner probing position
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Sorry for the upside down
But you can see that the Zero point is 0.090 inches lower (I have Carbide Motion set up in Imperial) That works to be 2.29 mm lower

Z probe on top of stock

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This agrees pretty well with the corner probe (the 0.004 inch difference probably could be a stock issue or an operator issue :roll_eyes:)

John

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Just to clarify, since you mentioned my post about BitZero precision, my errors were on the order of 0.1mm or less, so a completely different issue.

I still do not trust the BitZero fully and whenever I need precision better than 0.1mm (say, for two-sided machining), I do not use it.

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