[ludac]

I'm running a Suba CNC using Cam-Bam and Nc-Studio.

the machine is somewhat cheaply constructed but it's free for me use so I'd like to get it working to make things.

I've got a lot of experience in operating machines but less in the initial setup. So far I've gotten the machine cutting the right size, but not the right shape.

One issue I'm having is that the machine is failing to cut smooth curves, primarily on the y axis.

I've attached an example of what I'm working through. The blue lines are open, but only just. and very different from what gets cut.

any feed back on why the dxf cuts this way/what needs tweaking would be very helpful

I've tried feed-rates from 20mm/min to 400mm/min with no discernible difference.

I've had this happen on very simple arcs, circles cut with flat spots.

[ger21]

It's backlash in your Y axis.

[ludac]

Of course, that makes sense for the wonky curves, would it also explain how far off the line is on the X axis?
In the section on the lower left side of the P where the line nearly intersects. There is a jog of 1.4 mm off the x axis in the cut but only .001 in the dxf.

The motors are stepper motors as far as I can tell.

What do you recommend for eliminating the backlash? tightening the pinion on the racks? (the y axis is the long axis on this machine so there are two racks to adjust)
Could it be a problem in the relative motion of the two motors causing or worsening the back lash?

[ger21]

Youdidn't mention the X axis? Is the "S" too high? That's probably cause d by lost steps.
Are your pinions spring loaded into the rack? THat's the typical method used to reduce backlash in a rack and pinion.

[ludac]

Loosing steps is one problem that I think is happening to this machine, in the z axis possibly also other axes.

Looking at the cut again it seems like the backlash might be on the x axis, because the arcs at the top and bottom are curved (where the y axis is changing). but in places where the x axis is changing direction its got flat spots.

I've not been able to get into the machine to see how the pinion gear is mounted but I'd expect it to be spring loaded like previous machines I've worked with have been. I'll look into the drive systems on both the x and y axes see if there is an adjustment of spring tension or something similar.