Z axis not lowing enough to hit work piece

I am having a hard time figuring out what I’m doing wrong. I have programmed my tool paths in fusion 360 (which look correct in the simulator) and then posted to GRBL and uploaded with UGS. First off I tried to run the program by skipping the homing cycle. Just set up work piece zero to the top of my work piece and lower left corner as most CNCer’s seem to do. It will send the spindle through the proper z and x coordinates but right from the beginning, it will raise the spindle almost to the max then lower to within 3/4" of the top of my work piece. My work piece is 3/4" thick so i though I’d try changing my CAM setup origin to the bottom of the work piece…didn’t change anything. Bought limit switches and ran the homing cycle and tried running the G code again, but exact same thing every time. X and Y coordinates look correct but Z coordinates are always cutting the same height above the work piece. Tried a couple of attempts using G28 as well but same thing. Seems like the Z axis is cutting the same distance off the work piece as what the thickness of the model I am trying to cut out. IE i am trying to cut out of 3/4" MDF…runs 3/4" too high. Tried cutting a part from 1 1/2" MDF…runs 1 1/2" too high off the material.

Can you post a screen shot of your Setup/Stock pane (F360)?

Sounds like something is declared incorrectly.

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Make sure your post processor is adding a G90. Or you can enter G90 then run the code and see if it works.

Ive just posted a screen shot of my F360 Set up. Is this what you wanted to see? Let me know If there is anything else I can show you that could help :slight_smile: Many thanks

Thank you. I will Try the G90 command tonight and see what happens :slight_smile:

Your stock point is set at the bottom of your piece. You need to click “Box point” once and select the high corner “ball”.
You can see your three axis arrows connect to waste board level, you need to reselect and choose the top point.

Zeroing your bit on the top side of your material will make it carve too high as-is.

That’s it!! That was the solution. I guess after doing the homing cycle and having that set up properly, (maybe that along with the G28 command set up) I never went back and changed the point of origin back to the top corner of my work piece.

Thanks so much :slight_smile: