Z Probe after tool change


Just curious how I would go about probing zero after I run a 3d roughing pass, before the finish pass?

The material left on my project is no longer the same thickness (3/4") as it was originally and many changes in thickness in the bottom corner where I would be placing the touch plate.

Should I just flip the plate so the flat side is up and put it on another piece of material 3/4" thick and probe Z on top of that? Or place the plate on the corner of new material 3/4" and probe the circle?


Lots of answers depending on what you’re trying to do.

For a 3d cut, I most likely care about registering off the top. There are a couple of ways to do that. The easiest is to leave room on the original board that doesn’t get cut but does get flattened. Next easiest is to flatten to a desired thickness. Zero the bit off the waste board and manually move up the thickness and zero at that position. Easiest to perform but harder to design depending on CAM software is register off a reference that is not your board. For instance, I’ll register off a 123 block that sits diagonal lower left of work piece. Since I mostly work in fusion360, it’s easy to specify this fixture as zero. now it doesn’t matter what happens to my stock since the relation of the top-lower-left corner of the 123 block will alway be the same. I can recover my zero after an estop or taking off and replacing the stock.

For thru cuts and most design not needing to work to a specific depth from the surface, I zero off the washboard so what and where I’ve cut won’t effect my future ability to zero Z.

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Does your 3D roughing pass leave any of the original thickness behind? Mine always does, but I’m roughing with a 1/4" spiral end mill. I’ve (so far) been able to align my finishing bit directly over the uncut tiny peak, then balance the touch probe on that peak, then probe.

If you know the material is a certain thickness, you might find it easier to probe off the wasteboard for all of your passes.

The last method you mentioned would probably work fine too.

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Thanks guys. I’ll probably grab another board thats 3/4" thick and probe the plate off of it. In the future i’ll try and leave some room - But currently theres no original height left.

It’s worth noting when you probe a separate piece of material, if you’re workholding with tape & glue, you may want to do the same with your scrap piece that you’re probing off of. Not a huge difference, but you’ll be removing more material than you may otherwise have wanted to if it’s not secured the same way. And use it for ALL of your probes for that project, not just the detail pass.

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