Poor Quality Etching with M4

i have a noname 5.5mw laser engraver it is running GRBL 1.1f and when i got it i was testing power and speed setting and was getting beautiful results with painted tile im not etching the tile i am removing a top layer of paint to reveal the under color. originally i was using the default firmware setting and what ever the default lightburn settings were and results were great but a tile would take 3 hours the top layer of paint on a 4in x 4in tile so i started looking to how to speed up my laser as no matter how high i set the speed it was always slow i followed some tips on these forums and was able to get great speed by setting $32=1 but now i either get overburn where it burns all the paint off the tile on the edges or after about 1/2 way threw the burn the power goes way down i have used other software with the updated FW settings and dont have the overburn issue or the power fade issue but the end quality has a bunch of lines in the image.

i am not burning with the fill or line settings i am using an image.

befor i started messing with the firmware the $32 was set to 0 but now the laser dont act right with that setting.

what i am trying to have is the laser to run at the exact power i set no fade out if i do a bunch of test squares i found that since i did all the suggestions on these forums my laser power is weaker with the new setting but faster what i want is M3 laser power but with the M4 speed how can i achieve this.

sorry for the ramble but i have spent almost 2 weeks now trying to get this figured out and have seen alot of posts about the same issue but no real answer.

You can change the device profile to “GRBL-M3” instead of “GRBL” which will use the M3 (constant power) mode. That has its own issues, in that vector engraving will now have very burnt corners.

The better option is just to turn on “overscanning” in the image settings, so the laser has a bit of overshoot on either end of the engraving to speed up and slow down when it’s not firing.

If your laser is weaker with the M4 setting, it most likely means that you are asking it to travel faster than the firmware is set to allow. Read the 2nd half of this post, that starts with “with GRBL, in variable power mode…”: Configuring a 3018 CNC for use with LightBurn

thanks for the reply.

what i have read is using the GRBL-M3 option impacts speed as no matter what i adjust the speed settings too in the layer it does not change at all and makes all burns take 2-3 hours whitch is the original problem i had with the default settings when i installed LB and first turned on my laser.

is there a way to set up the laser an software to keep the speed i am getting when i set $32=1 an keep the laser power constant as what is happening now is the lasers power is fluctuating when $32=1 and the M4 is being used. basically i want M4 speed but M3 laser power control and consistency.

The M3 driver does not affect the speed, the $32 setting does.

Leaving it set to zero puts you in “spindle mode”, which means the controller is waiting for the rotary tool to speed up & slow down every time the power output level is changed. In laser mode ($32=1) the controller does not wait, because it knows the laser responds instantly to these changes.

Using the M3 command instead of M4 when in laser mode just means constant power output instead of variable. Otherwise the performance of the machine should be identical.

ok so i will give the GRBL-M3 device setting and see how it does.thanks for the reply i really want to get some consistent results before the trial runs out as i have bought tuns of programs for other this i wasn’t able to work to the bug out or see their limitations until after i spent the $$ and i really like how lightburn’s interface and ease of use is.

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