Z cut tolerance expectations

CNC Machines Shapeoko
1

I have been struggling with z axis tolerances and depths.
I have trammed, belts are correct, Belt stretch calibration with calipers. A 25 mm move registers 24.97 to 25.03

Cuts however that should be .06" deep are paper thin in some cases.
I am zeroing off the top of the waste board. part should be .50 inch think measures .47"
Material is cherry
?

2

Have you calibrated your Z-axis for belt stretch?

3

Change your file and try zeroing off the top of the piece you want to cut. Zeroing off the wasteboard can cause issues as you state your file has the material at .5 thick when it actually measures .47. So that will already create a shallower cut by .03. This will leave you with a .03 depth of cut based upon your .06 DOC

The rest can also be based up material hold down as if it is not clamped tight the board might have twist or cup that can also cause parts to be deeper or shallower in parts.

2 Likes
4

yes i have calculated z

5

the final thickness is .5 measured from the bottom. if the stock is a little smaller or bigger than specified in the program it should still get me to a .5 thickness

6

I’m sure you know what you’re doing and have already cleared the obvious - but for thoroughness:

  • You’ve surfaced your wasteboard recently (AFTER tramming)?
  • You’re using equal hold down pressure on all four sides of the piece?
  • You’ve reproduced the problem with a different board?
7

I’m sorry I thought you said your material measured .47 in thickness and your file was setup at .5 thickness. If its .5 like the file then yes there is another issue somewhere.

I would still try and zero off the top of your material, not wasteboard. If you run this test and it’s the same results then you can narrow down your problem further.

8

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