AtomStack S20 PRO distorted circles and shapes

So we got this laser almost two months ago and aren’t sure what we’ve done wrong (if we’ve done wrong)

Large plain objects mostly seem fine, but measuring them did show a slight miscalibration that I think I’ve fixed, but we still have significant distortion on circles and tight turns. The larger and smaller circles/stars are the same image just resized so you can see how distorted it gets. I’m just not sure what else I can tweak or adjust at this point. I’ve adjusted the belts, calibrated it, changed speed, power and some of it has slightly helped, but not when it gets to those really small sizes, and the person that paid for this is a miniature artist, so small details are important.

Any suggestions?

Can you upload the .lbrn file that was used to create these burns? Would help to understand where issues may be popping up.

This is the file I used. I originally found the circle and star from the Laser GRBL Accuracy Test, but I increased the size so it was more legible.

200square.lbrn2 (18.4 KB)

Took a look at the file.

Hard to say for sure but I’m almost wondering if you’re seeing binding. As in something is preventing the laser head from moving freely and smoothly.

With the machine off, if you move the laser head slowly by hand does it move freely and smoothly with very little effort to all corners of the machine? It should be very smooth, consistent, and require very little effort. Some say tilting the machine by 20 degrees should allow the laser head to move from gravity but that’s never been that consistent for me.

What you shouldn’t feel is the laser resisting movement or feeling like there’s excessive friction.

If you do find that there’s excessive binding this is generally caused by overtensioned belts or eccentric nuts that are used to adjust the distance of the wheels of the laser head assembly to the rails of the X gantry.

Do a mechanical review to identify where it might be coming from.

Outside of binding being a possibility, 6000 mm/min is quite fast for a line operation with these types of movements. Does dramatically reducing speed (like 500 mm/min) change the amount of distortion?

So the X Axis belt was preinstalled, so the instructions suggested that you aim for the Y axis to be the same tension and that’s what I’ve done. I’ve tried to pull slack from the belt (there was barely any) and tried adjusting the tension of the wheels to much looser or much tighter. It’s not exactly the same as the x axis belt, but it’s as close as I can come to it, and it’s not like they imply it’s that hard to set the belts right.

I did play around with speeds and just tried it at 500mm/m, the straights on the star is better, but it still has underlying distortion. Circles are still a hot mess.

I suppose this works if the X-axis was properly tensioned.

Belts shouldn’t be too hard to tension. They need to be taught but not stretched, with all slack removed from the line. As long as there’s no extraneous slack and the belts are taught that should be sufficient.

How does the head actually feel to move? The amount of distortion you’re getting would require fairly severe binding if that’s indeed what the problem is. It would feel more like you’re dragging the head around rather than it gliding. Are you getting any sense of that.

Can you upload an updated photo?

I’m a terrible person to ask this sort of question, I get really wishy washy. It doesn’t seem to be binding, it seems to move around with minimal pressure.

I redid it for this pic because I’m confusing all of my tests. Maybe I just need to attempt to calibrate it better? At the slower speed it looks much more like it’s just too narrow on the y-axis? The star actually looks a lot better in this one.

The slower ones look significantly better. It’s possible you have multiple things going on.

I think you’re right to check calibration. I suggest you burn a large square. The larger the square the smaller the impact of any measurement error. I suspect that will eliminate most of the skewing on the slower setting. You may still have some mechanical issues which are being exposed at higher speeds.

Cutting jobs with rapid movements in a very small size seems to be more prone to inaccuracies.

As the work size is scaled down, the limitations and inaccuracies of the motion system seem to be exponentially amplified, eg. very small and rapid movements are more prone to becoming absorbed by the motion system due to friction or backlash and so are not passed on in their fullness, or passed on with other errors or artifacts due to vibrations, or disparate axis characteristics…

Slowing the speed of the job will help, as will reducing the laser $$ parameters for Max Speed of X and Y, as the G0 travel movements if very jerky may contribute to a slight deviation at the next G1 move. However, rather than reducing G0 speeds drastically, a better approach may be to reduce the acceleration values on $210 and $210, particularly in Y - which is more likely to exhibit problems due to it’s increased inertia.

What I’m saying is - you may need to have different, more conservative settings to optimize for fine detail, then go back to regular settings for regular work.

For the detail work, try changing $121 to 800 and $122 to 200 (Y-axis acceleration), you can do this in the console area by entering:

$$ (first take note of your existing settings)

Then make the change with:


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Sorry it’s taken so long for me to get back to this. It’s become low priority since every time I mess with it we get barely any results.

Input the changes you suggested and there was zero change to the output.

I think this cutter is a lemon. Anyone ever deal with Atomstack customer suppport? (taking into account we’ve had this thing for months and only now realize it has serious issues)

@Ronath - Sorry to post to an older thread but I just bought an Atomstack A20 and am having similar issues with small circles not even close to being round. I am just starting to troubleshoot this and have not yet done all the checks and changes that you did above, but am planning to do them. I’m just curious, did you resolve the issue?

No we never did. The device is actually my roommates and I’ve gotten them to contact support because I personally thing the one we got was a lemon (like maybe a firmware issue? IDK), but right now the issue is less problems with Atomstack support and more with said roommate trying not to think about their $1500 doorstop and therefore procrastinating.

If you do have success, please pass it on. :slight_smile:

Yep, If I make any progress I will post it here. Thanks for posting all your previous troubleshooting above, this will give me a headstart…

I figured out my issue - the tension wheel on the bottom right side of my gantry was way too tight compared to the left side tension wheel. Once I loosened it up a little bit the gantry moves much, much smoother in the y direction and my circles are near perfect. Hopefully this will help somebody in the future if they are having the same problem.


I had the same problem with the circles and the solution was the same - change the eccentric and change the tightening of the lower wheels.


So I totally missed the reply back in December. The laser cutter has been in the corner gathering dust for 7 months and yes, what czech2767 said fixed it.

Apparently those wheels are supposed to be fairly loose…(instructions said "roll freely at a 45 degree angle, they roll a lot more freely than that now)