Help! CNC Coordinates and actual measurements do not match

[usaf0083]

Thank you for reading. I have a problem and I have no idea how to fix it.

I noticed that my CNC projects were smaller than what I had thought they would be. So, I decided to test it. I used the lower left corner as zero and then made the spindle drop at 10.25 inches (260.350mm). When the machine ran the G-Code, the machine dropped the spindle at an actual 8.25 inches.

I measured the board I was carving (it's 10.25 inches) and put the spindle back at zero. I jogged the spindle to the opposite corner and read the coordinates in CNC USB Controller. It said it was at 327.0563 when it should be at 260.3500. 327.0563 is over 12 inches. I'm at a loss. Any advice would be appreciated.

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[routalot]

I Know nothing about Planet CNC ,so treat these comments accordingly.I would suspect either calibration error (i.e. number of motor steps per mm) is incorrect or there is some mechanical slippage.Could be both.The discrepancy is close to 1.25 in both cases and I would be very curious about the other axes if they have identical steppers.

[RCaffin]

What Routalot said.

Cheers
Roger

[SkiPatrol]

This link might help ...

https://planet-cnc.com/how-to-setup-cnc/