Omtech not cutting perfect circles, hardware or software issue?

I don’t know if this is a hardware or software issue. I did a cut test file and a lot of my circles came out with little notches in them. I have cut other shapes that turn out great but not circles even on different files. I’m wondering if it has something to do with acceleration because I know that was an issue with certain things on my old diode. I don’t know if it’s acceleration issues or maybe it’s not going far enough after the circle is cut and when it moves to the next it caused that notch Or scan offset? Attached are some pictures if anyone could assist.

I’ve also double checked my axis which a 2 inch by 2 inch box comes out perfect with my tape measure. I could use my caliper to get a more exact if you think that’s a potential issue. Also my belts are as tight as they can be. I don’t think it’s a mirror issue because I’ve cut and engraved in random spots on the honey comb and everything that’s not a circle cuts out great.

Your results are symptomatic of a backlash problem, a common hardware issue. In LightBurn, Optimization Settings, you can enable ‘Hide Backlash’, if the problem with the circles improves significantly then you definitely have a backlash issue.

I have attached a small program called backlash test I have just made, which should provide an easy method to help you identify and measure backlash.BacklashTest.lbrn2 (166.1 KB)

Turn off Optimize cut path and run the program, it should start where it says start, if you measure with calipers the gaps a,b,c,d they should all be the same. X backlash will result in slightly greater b gap, and Y backlash greater d gap. With the top section I made the gaps small so it might be easier to visibly see a difference.

It is always better to identify the source of backlash and to eliminate it so that the “Hide Backlash” setting is not required. As well as checking your belt tension you should check your entire drive-train to make sure there are no places where there is “play”, check the grub screws, shaft couplings, drive pulleys etc.

It’s hard to describe but while the motors are powered on and holding position it is possible to push and pull on various parts of the drive train to look for any looseness/sloppiness or (click for example)movement where there shouldn’t be.

After you have done all you can to mechanically eliminate backlash, it may also be possible with some motion controllers to enter a backlash amount for each axis and the controller will attempt to automatically compensate.


You’re awesome, huge difference. I will play around with this but I did see Oz said it’d be ok to leave on for future reference and I don’t see any issues time wise with cuts. Any idea what it will affect outside of start positions/optimizations?

Well it’s called “Hide Backlash” and not “Fix Backlash” for a reason, which is that you will still have the exact same amount of backlash present which will continue to affect your work - it just wont be as obvious since “Hide Backlash” puts effort into making sure the start and end points match up.

This will likely not pose any problem for most of your work, but could be an issue for precise tolerance cut parts that fit alongside, within, or interlock with other parts - inlays, jigsaws puzzles, gears, die/jig making, or if you want circles without any flats.

And, as you will have already noticed, the cost of using it - is that you will lose access to half of the other optimization settings including the ability to set your own starting point, or to start at corners.

You could try using the backlash compensation at the Ruida Controller…

Did the BacklashTest program help you to measure your backlash?

From LightBurn, go into your Machine Settings,
Y Axis Backlash set that to about 0.24mm
X Axis Backlash maybe 0.08

“Write” the change, and run the circles again without Hide Backlash and see if it makes a difference.

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I didn’t get a chance to last night but I will try that. Thank you so much for the detailed help, you’re awesome! I will try this out tonight if I get a chance.

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