Z Axis plunging to deep

I’m lost on this one, I am using carbide create, Ugs G-code, I have my depth of cut at .05",
I use the paper method to set my Z axis never had an issue. Today the depth of cut is .10" deeper then set point, Ugs state at 0 for all axis, I have reset, reloaded program with no change, linear rails cleaned, backlash are good,
what am I missing, any help is appreciated,

I think we need more information to help. Are you running the same G-code or did the G-code change between .05" and .01"?

Hi Paul, I’m running the same G-code, cutting pockets,
it changed between .05’’ to .15" with a difference of .10" I have a jig set up cut three identical pieces until the last one, hope that make sense,

Did you set Z zero on the first piece that then cut the three pieces and the depth changed on the last or are you saying that you can set Z zero on a piece, cut it and your .10" too deep?

The first piece zero was set, the next pieces zero was in the same start position, what I usually do, after cutting the pieces is the following;
1.return to zero
2. raise the Z axis
3. change my material
4. return to zero, check start point and start next piece,
for some reason the last piece it decided to go .10" deeper then set point, when I returned to zero it was spot on from where it started,
I have since noticed if I cut a piece to be 4.5" wide, outside cut using 1/4"end mill my piece ends up being 4.75" wide, something strange is happen, I have checked my tool path and bit selection several times all is correct,

Very odd. If the last piece was thicker, it would appear to cut deeper, but you would notice this when you did your return to zero check. Also, it’s possible for the Z axis zero position to get screwed up if you run the Z axis into something and the belt slips a cog (if its loose) or the stepper motor can’t step as told to. Again, I would think this would have been caught by your return to zero check. Also, it is possible for the bit to slip in the chuck if not properly inserted and tightened or if there is too much sawdust in the chuck. Again, I think that you would have noticed this with your return to zero check.

On the last comment, it makes a difference if you do an “inside,” “outside” or “on” cut. Your cut seems to be off by a bit width which would be the difference between an inside and outside cut. If you tried to cut a different width is is always off by 0.25"?

On the second piece, you clicked return to zero and the bit was just touching the material, correct?

Did the DRO in UGS say that Z was equal to 0?

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Thanks Guys, checked every thing mentioned no bit slipping as it returned back to start position every time, checked tightness of bit, Im also cleaning cleaning and more cleaning, rails, wheels, checking backlash etc. Just to mention that outside cut being off by 1/4" was on that last piece as well,
Thanks for all the helpful advise, will play around tomorrow night make the same cuts and see what it does,

Returned to zero every time, no issues with that, DRO was 0, it was weird, will try tomorrow, Thanks

@jaybird Damn! This is getting difficult. :upside_down_face:

We are into WAG territory now, Jay. Is this problem present in only the one file, or with others, too? Can you post your gcode file? I don’t use Carbide Create so I can’t help at all in that regard, but the gcode file may show something weird.