Back to regular broadcast: that last test card: Moire looks pretty identical for any frequency. But worth to note that it is not the fact that 10K and 20K are valid values and controller actually producing it. Have you checked with the scope? I know 1,2, 4 and 8K are valid frequencies. It is possible that last test card is not valid because controller not necessary able to produce these frequencies. I would suggest to repeat at binary frequency sequence above. I also refer to previous test at 8k that has noticeable difference. Need good explanation for that.
Otherwise I would agree with OZ (who wouldn’t !?!?) that is it a wobble. Get new rollers and tighten everything. And run slower, less acceleration. (GRBL still don’t have jerk control, I think, though available computation probably allows it now. Maybe next version?)
I have another observation. In previous test low power lead in-lead out was cropped. Now it is smooth. No longer choppy fill. What is the difference? Something else has changed.
Maybe are not valid but there’s a result difference so I think the controller is using the new values.
Sorry no I don’t have a scope to check the frequency.
In this test I used cardboard instead of painted glass. Paint on glass is thin and react at minimal variations of power.
I have some more tests that can prove that is not just a speed problem:
In this is quite clear that the Laser is pulsating, near the border is traveling slower so the pulsations are closer and when it speeds up they become more distant. This explains why at lower speed the pattern is gone because the pulses are so close together that are overlapping.
Ettore,
I’m agreed with your conclusion. That pattern over apple looks like laser power is unstable and in sync with burning.
Can you tell more details?
It this brand new setup?
Was it ever working right?
Did this Moire onset instantly or gradually?
So what can make it unstable?
Laser head itself. Caps may go bad, making it unstable. The very next thing I would try is to swap that laser head.
Cable. If gauge is too thin and signal is low - ground lift at laser end can do this trick. (if brand new build.)
Try render it with M3 vs M4. this may give some hints.
I hardly can believe that firmware can do that. But who knows! If you go that way: FluidNC is specifically made for ESP32 and installation is super easy. GRBLHAL is another alternative but very involved in compiling and configuring.
The Laser is an Atomstack P9 M50, I made no modifications so it should be supposed to work out of the box.
I’m in contact with Atomstack to diagnose the problem, I will post more if I find a solution.
I’ve been using my boxford 80w co2 laser since Nov 2021 and found that i too get this issue. I have used my machiine at every speed it is capable of (up to 1000mm/s but i mostly engrave at 500mm/s) and this same strange ‘pattern’ appears on every engraving job i do, but only using lightburn.
When i use the latest version of rdworksv8 with the same files at the same speed/power settings, it disappears completely. I have been mitigating this problem either using crosshatch feature which is far too slow, or vector line edging engravings, but any large engraved area and it will immediately show up. At that point, i have been exporting to rdworksv8 to then complete the job perfectly.
I will get some pics to demonstrate when im at work tomorrow.
This is using LaserGRBLwith 3000 speed and 20% power M4
I should say that in picture is not so evident the pattern, but it’s possible to see that Lightburn creates lines that follow like an offset border, while LaserGRBL doesn’t create such lines.
Here is a pic of this problem happening when i use lightburn. I completed this job succesfully by using the same file in rdworksv8. No strange banding or lines.
But it is burnt as a raster, it does not look like vector with fill. None of images posted has perimeter as a vector.
Maybe it is converted to raster? Vector fill will be flat line. Raster will be collection of short lines for each scan line.
Can you post your source and also save .NC with that bad moire and post it here as well?
Have you found “Dot width correction” settings? Tried to turn with it OFF?
Just to be clear, it’s not an image but a fill.
Anyway today I received a new laser module, the cheapest one I found on Amazon and the problem is gone totally.
So as I supposed is not a problem of speed or wobbling, is just the laser is not able to keep constant the power output.
Cheap Chinese 20W laser module
Atomstack have a nice fine dot that works really well in cutting but looks like not much suitable for engraving.
It will be interesting to understand why with LaserGRBL there’s much less noise.
Can be as simple as bad cap in the laser driver board.
Different results between LightBurn and LaserGRBL are indeed intriguing. If you post NCs from both - maybe we can find something.
If that laser otherwise so good- you maybe able to purchase matching driver board for small fraction of the cost of new module and swap that it. Should be relatively straight forward. Or if it is so new - swap under warranty.
Just to update you, I bought another Atomstack M50 module and it behaves the same, so the issue it’s not a faulty module. I’m not totally sure if I can find different settings to resolve this. Slowing down the speed makes the pulsations closer together and it masks the problem. It’s also strange that there is a smaller line, looks like that the compressed spot is not resulting in a uniform laser beam. The issue is also changing day by day, it’s not replicable so can be that when using LaserGRBL it was less visible just for luck. I think Lightburn is not an issue here, so this issue can be closed.
Ettore,
Thanks for the update, very interesting.
There are very few things that can make such pattern. The fact it changes by day is a hint. PWM from the machine is crystal clocked. It is software processed and modulated, running the exact same job should produce very similar results.
There are non-crystal locked frequencies in the system that can change as environmental conditions are. Most power supplies, including laser current source inside of the head, are free running and will be modulated mostly by temperature, but possibly by other factors as well.
It is possible that problematic head has electrical design defect, like unstable current control for the laser.
Stretching possible causes - thin wires or bad.high resistance contact can disturb current control and cause it to ring on transient load, that is switching from off to on.
If you care to experiment further:
I would try to play with PWM frequency, but not the round numbers but I would try to tweak some odd numbers. Not sure if your controller would take it, I would definitely check with scope if controller actually changes the frequency and what actual value is.
Then I would consider to scope the power feed into the laser head, at the laser head. Some heads can be more immune to power instability than others. Can be something specific to the way your machine is wired. I would expect 12V to have no more than 0.2V p-p noise+ripple. If more - I would consider trying different supply and wires. Supply not necessarily with bigger amperage, but with cleaner and more stable output. Just for the test, maybe a good quality lab supply.
If you will - keep us posted. This appeared to be pretty popular machine. I’m sure more folks are interested to know.
That looks like that patter could be wobbly lines. Inertia, when the Y axis moves for a line shift, stops suddenly and wobbles while the engraving is running on the X axis.
Do an engraving/fill/raster at 0.5mm line interval and you might actually see it then. If it is that.
Uni-directional fill will probably resolve this issue for you (Turn Bi-directional fill off). But the run time will double.
