Plasma table

On my small CNC plasma table… if I go to make a small square, say 6x6in. The X is always 6 in. But the Y is always short 1/8 of an inch. I have checked for loose Motor Parts loose connections and made sure everything is tight it’s continuously off 1/8. I use inkscape so I’m not sure if it’s going from inkscape to sheetcam or sheetcam to mach3. Also when I calibrate everything is exact… Y moves exactly what I tell it… X moves exactly what I tell it …so I’m not sure where the problem is.

The 2 things I can think of: (assuming you have stepper motors)

  1. When you turn on your controller, the motors should lock up. You can then go to each axis and try to move it by hand. You should not be able to move the axis except with a great amount of force. This should reveal any mechanical problems.
  2. The acceleration on your Y axis may be too great when running a program and may be loosing steps. You might try setting the acceleration on your Y axis a little lower (it generally has to move more weight than the X axis) and see if it makes a difference.


Look at the gcode and see if it contains the correct dimensions. If it does, then it has to be a Mach or mechanical problem. If the calibrations match in Mach, then most likely losing steps as WyoGreen stated.

That’s just it the dimensions are incorrect In sheetcam

I checked all all the mechanical stuff… When you go to calibrate you tell it to move 1.001 it moves 1.001… You tell it to move 2.156 it moves 2.156 the table is cutting exactly what it’s being told… the g code is incorrect In sheetcam it’s either coming from inkscape or somewhere else I’ve even tried AI. And it’s even worse I’m at a loss…

In SheetCam use the measure tool (right-click->measure) to check the dimensions of your drawing.
Have you tested for lost steps? Move the machine to 0,0 (or any convenient place). Make a mark on the gantry that lines up with a point on the Y axis carriage. Now run your cut then move the machine back to 0,0. Does your mark line up? If not you are probably losing steps.

I’ve done that I’m not losing any steps… the dimensions are wrong in sheetcam. If I tell it to make a 6 inch square it’s making a 4.8 inch square in sheetcam that’s what the dimensions measure in sheetcam. The table is making exactly what sheetcam is telling it to make.

If your drawing is for a 6" square, SheetCam shows a 6"x4.8" rectangle and that is what is being cut? I’d say it has to be in your drawing. Just for kicks. Rotate your drawing in inkscape 90 degrees and see if it still shows up in SheetCam as a rectangle. If it does then inkscape must be exporting it scaled by 80% in one direction. I’m not very familiar with inkscape, but there must be a scale setting somewhere that is set wrong.

Could you send me a copy of your 6" drawing. By the way, are you using svg or dxf? Inkscape generally works better with svg.

yes I will. I sent it… not sure if I did it right… And yes SVG’s

Thanks for the replies I was able to get it figured out. I had to take sheetcam off the computer completely. Put it back on machine everything works great.