Odd step skipping only on low z axis cuts

Shapeoko XL. I’ve been trying to figure out a problem. Had done a few projects no problem, then I tried making some ornaments from 1/4" cedar planks. The file cut out 2 ornaments, 1st a pocket operation on each, then the outline.

It started making stair steps in the +Y direction as it cut down. 1st odd thing was that after each of the 4 operations, it came back and started at the right place. I would have expected the drift to accumulate, drifting farther up the Y axis but it reset after each cut.

So I’ve spent a bunch of time tightening belts, adjusting eccentrics, and checking the set screws. Nothing changed it.

Then I changed the wood I was using to test, this time a 3/4" thick piece only cutting in 1/4" down. It then it didn’t step that time. Thinking I fixed it. I tried the thin wood again and it drifted again. So I mounted the thin board on the top of the 3/4" board and it cut correctly.

It seems that the drift only happens in the 1/4"-1/8" closest the waste-board. Although I have a way of getting around it, I worry that the problem will show up in other ways.

Any ideas?

What Z axis do you have and what is your setup like (do you have a supplementary wasteboard on top of the baseboard ? you should). It sounds like you might be very near a mechanical limit at the lowest Z values, maybe try zeroing on the baseboard surface and observe how the Z axis behaves while doing it ?

1 Like

No, I don’t have a wasteboard yet ( I will be making one next). Was on my list but sidetracked when this error came up.

I have been zeroing to the baseboard. I haven’t noticed any wobble or Y movement, not to say that means it isn’t there. I’ll play.

so do you have the stock Z, or Z-plus, or HDZ ?
Just asking because there have been multiple threads recently from Z-plus owners coming to realize that they don’t have enough reach (or barely enough) to touch the baseboard, and who added a wasteboard to fix that problem.

1 Like

The stock Z is what I beleive I have. Uses a belt and spring vs a screw

1 Like

Ok, thanks for confirming. For the sake of testing, you might want to remove one of the two springs, and see if it fixes the issue (see this old thread for example…it happened in the past for some people)

But really, you’ll be better off with a wasteboard anyway, so that problem is a good incentive to install one :slight_smile:

1 Like

Do you have a dust shoe (in particular the ‘Sweepy’. I have seen a problem with the stock z axis as it tries to fight the force from a dust shoe as it starts to get really compressed between the z axis and the part being milled.

No, no dust shoe. Good to know as I was thinking about getting one.

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.