Recurring "Wiggles" Problem

When smooth curve cuts have “wiggles” or “vibrations” I think of mechanical problems. In the past, these problems can be solved by changing configurations (speeds, accelerations, etc.) or making mechanical adjustments (upgrade steppers, oil bearings, etc.) However, this “wiggles” problem has us stumped.

Compare the design below to the cut below.
Note the wiggly lines that occur periodically in the cut.
Those cut lines are not a single pass but two identically flawed passes.

(If the problem was mechanical then it wouldn’t present exactly the same way twice.)

Does anybody have any idea what the problem could be?
For background, this is just an image that was traced using LB.
Also, we’ve lowered both speeds and accelerations but to no affect.

For the record, we run RuiDa controllers (6442G) and currently LightBurn 0.9.21.

You seem to have checked a lot of things, how about a loose lens?

Good option but a loose lens would “rattle” randomly.
The problem we see is repeated exactly each pass.
Every pass the “wiggles” are in the same places.

If you run the same job with half (or twice) the speed, do the wiggles change?

When I zoom into the original design image the lines are very wiggly and pixelated. Maybe doing some smoothing on those lines so the vectors are much more smooth and uniform?

Also, a loose belt will get you repeatable results as long as you are consistent with the operation. ie if you repeat the same approach to cutting, ie cutting out a square going clockwise start at upper left then repeat that. Vs doing the first pass clockwise and second pass counter clockwise.

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A lot of start/stop (accel/decel) in a certain area could set up resonances that could amplify the movements. @DougL 's suggestion of smoothing is a good one.

I would LOVE to believe that our machines were of such consistent quality that a resonance could repeat mechanical vibration errors consistently. :slight_smile: Knowing the machines as I do, I have my doubts but I can add it to the list of things to test.

Doug, what I also should have said is this file has cut perfectly for years.
It’s used as a first exercise in our Laser Cutting Introduction class.
Still, someone could have messed with it so I’ll revisit.

I looked at that image again and on 2nd look it appears to be a camera image of the work area in LightBurn and not a screen capture. Can you post the file so we can take a look at it?

I would also try changing the direction of the cutting operation and verify it’s different in the Preview and see if the wiggles change. If they do then it’s surely mechanical, if not and nothing else being cut has these wiggles, then it’s something in the file.

If used on a public computer it might be helpful to change the attribute of the file to read-only and have users open it and then use save-as if they want change it. New users might want to try changing settings in LightBurn and watch how things change in the Preview and then when exiting, by habit, save it when prompted.

Have you looked at the configuration of the stepper motor drivers for your X andY axis? You could have a frequency mismatch or the frequency configuration may be completely wrong for your particular stepper motor. Another thing to consider is the Ruida controller configuration for your laser which could cause issues if you have some bad configuration parameters in there.

As a test, cut a few regular circle at various speeds and see if you get the same kind of wiggles.

Other things to look for are lose belts, over tight belts, and lose stepper motor gear, but the fact that the wiggles are consistent suggest a stepper motor signaling issues which goes back to the drivers and the Ruida controller configuration for your laser.

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