Help! The X-Axis on my new machine goes out of alignment when creating curves/circles

Hi all,

Hopefully a simple answer to this one. My new X-Carve (bought assembled but never used) will engrave fine when working on only one axis at a time and even when carving a diagonal. But as soon as a curve or circle is attempted, the X axis only will lose millimeters on each pass. I have re-built the X axis carriage and re-tensioned the belts and thus don’t believe the issue lies there. The thing that intrigues me is that the diagonals have no problem (obviously running on bath axes simultaneously), but once curve variables are introduced the problem shows up immediately.

Any advice much appreciated!

Do you have the Arduino + gshield or X-Controller?
Are the steppers on your machine 1,7" or 2,3" wide across their back plate?

Hi, I’m using 2.3" motors with a Gecko G540 controller.

Isn’t that a wheel issue? If they’re not tightened properly?

Hi Adam, Yes - I thought that too, but it seems to happen no matter how tight (or loose) the wheels are. I was wondering if it had anything to do with electrical interference across the cables as both motors are receiving current at the same time (and the cables are housed together in the drag chain) but I’d assume this would affect diagonal (straight line) cuts as well. And the cables are all shielded.

Doesn’t make sense that it would be a belt or motor issue if the rectangles are carving just fine. Those angles would also be carved incorrectly since those are multi-pass carves too. The circles are also not out-of-round, it’s just that the X-axis is shifted to the right as the carve progresses. Interesting problem…

It appears to me that you have a motor losing steps on the right hand side at the same point every time. I would think that would be related to a mechanical issue, such as a loose set screw on a motor pulley, or perhaps a loose motor mount.
At the point of the flat in the circle, the torque from the bit would be directly applying force against one side of the axis. If that right side motor is losing steps or simply loose, it would allow the bit to move to the left, which is what I see happening.
I’m unfamiliar with the Gecko drivers you have, but do they have a Torque reduction setting at idle? If so, make sure it’s turned off, as well as checking all the stepper pulleys for tightness and applying locktite.

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Thanks for the suggestions @AlAmantea. The pulley set screws do appear to be quite tight but maybe a re-check is required. I’m not sure about the torque reduction settings either, but will do some research. Will keep you updated.

Re-seat them using Loctite.

As both axis (X&Y) are running while carving the circle they are neither idle and no current reduction function should kick in.

What are your acceleration rates for X&Y?

They’re both set to the same value = 100mm/s. Should i increase these?

Not yet.
This still appears to be a mechanical issue to me.

Have you checked the Z axis mounting to make sure there is no side to side play and that the Z axis is fully trammed (vertical at 90 degrees)?
I looked at the photo again closer, and also see some minor step issues in the diamond shape on the upper right and lower left diagonals, which relates to tension created from bit rotation.

I wonder if the Z axis is loose on the delrin nut allowing the axis to twist during a diagonal move. In addition, I would double check the V wheels on the Z axis, and make sure there is no movement from side to side.
An easy way to check this is to install a short, small diameter bit in the router, lower the Z axis to the wasteboard placing a ruler under the bit. by physically grabbing and flexing the Z axis from left to right, the bit will indicate how much side to play you have on the ruler.
It is possible to do this, and maybe trace your issue by a visual inspection to locate what is loose.

I would also double check the X axis pulleys for slippage, as well as checking the V wheels and their mating runners for debris, reset the tension on the X axis belt,and giving everything a complete cleaning with a stiff bristle brush and a bit of alcohol.

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You haven’t said what software you’re using to send gcode.

Hi, I’m using CamBam to create the GCode and Mach3 for the machining.

Hi @AlAmantea. I’ve run through the mechanical checks as suggested and cleaned the runners/v wheels. The interesting thing is that I can do a trial run and it works perfectly but then a short time later things go awry again. Wondering if it has anything to do with the steppers heating up? Watching the cut it’s quite clear when the X-axis just “takes a break” at the start of the curves then kicks back in. That’s why I’m musing whether it has anything to do with the torque/acceleration/velocity settings.

The steppers dont mind the heat (unless pushed past 175degF) but the stepper driver may reach temperature that trips the temp. protection of the driver. I dont know the G540 so can not comment on its capacity.

The settings you mention can all affect the “load” of the driver and playing with these can mask you symptoms - but the core of your issues IMO seem to be within the driver current limit/over.temp protection.

Measure your resistors governing the current limit for your X-axis.

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Use an ohm meter to check continuity for all 4 wires of the x axis (machine turned off and unplugged) while sliding the x axis slowly left to right.

Post a copy of your machine settings, please.

Also, have you set the torque limit switch (dip switch 4) off?

He uses a Gecko540 controller board with integrated drivers :slight_smile:
(3.5A/50V capable)

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Thanks. I missed that!