[Oakfield]

I have a 1300x1300 CNC Router, which looks identical to the Spartan in the attached image.

The problem i am having is that if i cut 2 identical size panels about 600mm wide side by side, the one on the left is about 1mm smaller than the one on the right.
The one on the right is the correct size, the one on the left is undersized.

The X axis runs on 2 linear rails and a rack and pinion.
My instinct was something wrong with the rack - it is in 2 lengths.
I have ruled this out by swapping the 2 lengths with each other, and also swapping with the y axis - no change!
I have swapped the stepper motor, pulley, belt, and pinion - no change!
I have tried running the same toolpath file from the zero point and again by zeroing at x600 - still 1mm different!
I have tried cutting the shape by manually jogging the machine to the correct coordinates - Still cuts under sized!
The machine is flat, square and level.
It is running on a UCCNC eth400 controller and Vectric software.

I have run out of ideas and patience - Does anyone have any ideas what could be causing this impossible problem??

Thanks!

[awerby]

What happens if you cut one panel 1200mm wide? Is it over, under, or skewed?

[Oakfield]

What happens if you cut one panel 1200mm wide? Is it over, under, or skewed?

It is also 1 mm under if I cut a 1200mm panel.
What is really confusing, is that i have manually jogged it 100mm whilst measuring the movement with a digital vernier and it seems to be within 0.05mm all the way along the x axis.


It just isn't making sense in my mind and i have run out of ideas to try!

[awerby]

Is your X axis driven by one motor or two? In a two-motor system, they are supposed to be slaved together, but sometimes they lose synch. In a one-motor system, it's easy for the gantry that spans the table to get out of square. If the rack and pinion is driving one side, the other side can lag a bit. Have you checked your cut panels for squareness? Try measuring diagonally, left top corner to bottom right corner, then vice-versa, and compare the two measurements.

[Oakfield]

Is your X axis driven by one motor or two? In a two-motor system, they are supposed to be slaved together, but sometimes they lose synch. In a one-motor system, it's easy for the gantry that spans the table to get out of square. If the rack and pinion is driving one side, the other side can lag a bit. Have you checked your cut panels for squareness? Try measuring diagonally, left top corner to bottom right corner, then vice-versa, and compare the two measurements.

The Gantry is driven in the Y direction by 2 motors, one either side with linear rails and rack and pinions - This has no issues and works perfectly.

The X axis is driven along the gantry by a single motor with a rack and pinion, with 2 linear rails.
There doesn't appear to be any backlash or play, and the rack is parallel to the linear rails.

Thanks for any suggestions so far.