I had a project where I mixed 1.6W laser, 10W laser and 40W laser, and I had a lot of setbacks and frustrations, which I decided to investigate a bit further. Here the results - spoiler: Inline power implementation for the 10 W is buggy, and trapezoid power implementation is not working or buggy.
Lightburn, 10% oversan, bi-direcional line fill, constant power
Lightburn, 10% overscan, uni-directional line fill, constant power
Lightburn, 10% oversan, bi-direcional line fill, inline power
Lightburn, 10% overscan, uni-directional line fill, inline power
Luban, 10% overscan, constant power (bi directional, cannot be changed)
Luban, 10% overscan, inline power (bi directional, cannot be changed)
Luban, 100% overscan, constant power (bi directional, cannot be changed)
Luban, 100% overscan, inline power (bi directional, cannot be changed)
Trapezoid problem is the same, but in addition, the edges, when using inline power, are not straight any more. The laser turns on and off at the wrong positions. I assume they botched the inline + trapezoid implementationā¦
Good: With more offset you can compensate for the burnt edges in constant power modeā¦
Lightburn, 10% oversan, bi-direcional line fill, constant power
Lightburn, 10% overscan, uni-directional line fill, constant power
Lightburn, 10% oversan, bi-direcional line fill, inline power
Lightburn, 10% overscan, uni-directional line fill, inline power
Luban, 100% overscan, constant power (bi directional, cannot be changed)
Luban, 100% overscan, inline power (bi directional, cannot be changed)
You canāt see it well, but with 10% overscan again burnt edges, so trapezoid still broken.
Conclusions:
10W Laser with inline power will spoil your results
When using scanning techniques (line fill, photosā¦) make sure to have enough overscan activated if you use constant power mode
When you use anything like āon the pathā or Lightburnās offset fill, youāre screwed: With trapezoid power not working properly, the speed changes of the laser with complicated shapes will cause inconsistent engraving depths. This is painful, as it takes away a lot of use cases!
I guess Iāll bother support with that - they need to fix these bugs.
And hereās an update: Turns out Iām wrong after all regarding Trapezoid power!
I asked in the Lightburn forum if the offset fill job setup could be modified so that at sharp corners I get overscan. This led to a bit discussion, which finally let me understand how things work - I seem to have been exeptionally obtuse here not understanding this earlier:
Constant Power Mode means laser is started with M03 - and this actively switches OFF trapezoid/s-curve power
Non-Constant power mode starts the laser with M04 - and this activates the power compensation
Inline power is just independent from that. ā It is a beast of its own, and I need to test this separately. It is neither M03 nor M04, but the G1 command include Sxxx - and if this properly uses trapezoid power I need to test - laterā¦ EDIT: See below - no trapezoid power with inline power
Now comes the mean part which made me despair: Lightburn Snapmaker profile has a bug - regardless if I select constant power mode on or off in Lightburn job setup, it always issues M03, i.e. constant power in the GCode! And that lead me to believe trapezoid power is faulty in the Snapmaker implementation. I apologize for my wrong accusation!
Some people say (incl. Lightburn support): If you have issues with the Snapmaker profile, use GRBL profile, works just fine (it, e.g., addresses the problem with Air assist). So I tried GRBL - but this then has a problem with my much loved offset fill job setup - the laser turns off after the first move.
Long story short: I will do three things:
Try to convince Lightburn to correct the Snapmaker profile for this plus air assist
As long as the bug is there run a searchānāreplace over Lightburn GCode to replace M03 with M04
Reveisit this test here, as my interpretation of the results may suffer from the Lightburn bug: Laser Inline Power processing slow?
EDIT: I guess I should also revisit PCB etching with the 2Wā¦ would suffer from the same bugā¦ Huh, lots to do the next weeksā¦
What remains is the problem with the 10W. This also is visible with Luban generated GCode.
Finally, hereās a picture of my tests:
Top row - unmodified Snapmaker profile output: First: Square, offset fill, constant power OFF, next: Square, offset fill, constant power ON, next: Square line fill, constant power OFF, 5mm overscan
Middle row: Same setup, but GRBL processor
Bottom row: Same setup, Snapmaker processor, for second and third square manually replaced M03 with M04 ā Success!
I got some interesting results for you. I was going to do a test of using G0 for overscan, and decided to rerun the test with M4 as well just to see what the hell. For reference; Iām using GRBL-M3 in Lightburn for this test. It seems doing a find/replace of M3 to M4 using this profile actually works fine. However, the regular GRBL (no M3) with variable M4 mode does not.
Anyway the results! I purposefully ran the power a little light so variations in power would show up better. 0.5 fill to identify each line, along with a line mode for an outside trace. This is with a 10W.
Bottom left; Regular M3, no G0 for overscan.
Bottom Right; Regular M3, G0 for overscan.
Top Left; M4 swap, no G0 overscan.
Top Right; M4 swap, G0 for overscan.
That top left with M4 looks pretty clean and even. Bottom left was pretty much as expected for M3, corners a bit darker, but otherwise good. The G0 for overscan in the bottom right was a bit of a shockā¦ why are the edges darker. However, both M4 results look decent, and the very tips of the corners seem to fade slightly, so the power is pulling down a smidge as it should.
Iām surprised that the M3 squares look differently. I would have expected the left bottom to look the same like the bottom right, as the laser should accelerate and deccelerate at the edges in both cases.
Would you mind to share the GCode? Would love to understand thisā¦
Thanks again Aaron for pointing me to Snapmakerās profiles.
If you do not want to connect via Serial but just export GCode and transfer it, and if you use absolute coords, you may even use the 40W profile, switch off the laser offset, you can use one profile for all lasers. The GCode is basically interchangeable between all Snapmaker laser modules.
In addition to the āEmit S valueā¦ā change, the Snapmaker 2.0 profiles state a work size of 400x400 mm - thatās the Artisan size. But this is easily mended via Edit Device.
Hereās the GRBL test (same job setup as in my second post) with 1.6W, 10W (bug still there - Snapmaker ticket open), and 40W (Air Assist working):
Not perfect - but this is to be expected: the power compensation algorithm not necessarily matches the material reaction to the laser, which most likely will be something very non-linear. Thus with wood you get the white cross with offset fill. With other materials it might be better.
Oh, and last remark: The 2W IR laser profile from Snapmaker now adds Air assist (which does not make sense, as the 2W does not have Air Assist), but uses the Marlin base and has the M03 bug - M04 is not used - I discourage the use of that oneā¦
Ah, I get the difference. In the āNo G0ā variant, overscan is done by G1 commands with S0 - laser power 0 - i.e. inline power. In the G0 variant you switch laser on/off via M3/M4 - M5 and then do the G0. And thatās basically the āoldā behaviour: With constant power and G1/G0 moves interchanging, the laser always stops on movement change.
Still, it inspires me to test if M4 + inline power would mean inline power with trapezoid if I only use G1 movesā¦ Huh, will test later.
I was going to do a test of using 
