Issue with running a deeper profile toolpath

Hi Guys,

I was cutting 1/2" plywood earlier this evening. I set my profile toolpath to cut at 0.505" deep. It didn’t quite cut through the plywood, so I went back to V-Carve, set the cut depth to 0.510", saved it, loaded it and re-ran it. It still came up short. I did the same thing 3 more times, each time setting the DOC a little deeper, but the end result seems to be the same. I finally got frustrated and shut it down for the night until I could hear back from one of you guys.

What am I doing wrong? Is it because I didn’t re-zero my Z axis? I didn’t think I had to since it was already set from the top of the material. I figured the new toolpaths with a deeper DOC would do the trick.

Please help so that I can sleep tonight. Thanks in advance guys!

Did you measure the actual thickness of the plywood to know what cut depth would be sufficient? My first thought would be the wasteboard isn’t flat and coplanar to the machine which might leave low spots in the wasteboard where the bit doesn’t cut all the way through. You could try changing your setup to use the wasteboard as zero so the thickness of the stock becomes less relevant.

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Thanks for the suggestions. I did measure the thickness of the wood before starting the project. I also have made sure that my spoil board is flattened and the set up has been trammed. I’ll try zeroing off the spoilboard surface tomorrow and see if this helps. Cheers!

Don’t forget to regenerate the toolpath in V-Carve using the bottom of the stock as your zero point otherwise you’ll cut into the waste board.

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Consider setting you cut from the bottom of material (surface of spoilboard) in your design and then probe from the spoilboard. This should eliminate the problem if in fact you spoilboard is coplanar to the router

Are you sure the bit isn’t moving slightly? If I’m zeroing off of the spoilboard I like to take the joypad and touch it to the surface of what I’m planning on cutting. If it’s 3/4" wood I expect the Z axis on the screen to read .75. If it’s not then I try to figure out why. If it’s the wood I make an adjustment in the code.

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I’ll def check that out and let you know. I always zero off the surface of the material, so this will be a new experience going off of the spoilboard.

Choosing where to zero can help with achieving a range of manufacturing output you want in going from design thru material variation to final product. By manufacturing here, I mean the M in CAD/CAM.

For instance, when I need to be a certain depth from the top, I zero off the top of my stock in the setup. Flatten (as a CAM operation) from stock top to model top. Then whatever operations to carve the model from the stock. In this case variations in my stock thickness (as long as it is thicker than the deepest cuts!) are mitigated and I “start” with a flat surface parallel to the x-y plane at z flattening height.

When I want to cut all the way thru the stock and/or need stock to be a specific final thickness, I setup CAM z-zero on the surface of my waste board. Flatten to whatever thickness I need from the part so I know I have a specific depth even if my stock has some variations…with cnc work I use the bandsaw much more and rarely thickness plane any more. It’s longer to flatten on the cnc BUT the overall time is shorter since I entirely avoid planer setup time as well as the lengthy tetris game I need to move all my tools around a small shop. Additionally, I can have my final cutout/contour operation leave a few thou for the blue tape-super glue holding the piece and not gum up my bit or cut the waste board unnecessarily.

For tricky multi side cuts, I’ll model a fixture in CAD that assures repeatable alignment and re alignment of the stock. I’ll zero off a fixed xyz corner of the fixture. Before cutting the piece, I mount the fixture and cut it in place so it is exactly as modeled.

Other times, I’ll pick a specific model corner that I use for all six sides and reset xyz to that corner every time I change stock orientation. This usually involves thinking thru both CAD and CAM to ensure I have enough 90° edges that I can lay flat on the waste board and square to and x and/or y fixture. This is the most error prone for me since there is a new chance to screw up with every orientation change. However, it is the best (for me) in ensuring all cuts are precisely relative to a fixed point so the geometry on the different sides line up and there are no seams.

To;dr Consider using different zero locations to achieve specific results in your manufacturing steps.

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