Strange results with GRBL

Hello, I recently reformed a cow 40w laser to work with grbl, I have the same problem, I do different powers and the laser does not activate at the right time, it has a lack that with the board it had it did not have. How can i fix this? Thank you.

Can you show a picture of what the design is, so we can see what it’s supposed to look like?

Are the numbers speeds, power values, or something else?

I send you the photo. It would have to be a 10x10mm square. But it is as if the laser takes a long time to activate and the movement has already been initiated. I use translations to be able to write English, I’m sorry if you don’t understand clearly.


In the case of the word hello in Spanish “Hola” and the rectangle looks like it does not make a print run, making stops and leaving blank parts. Thank you.

Was that done using “line” mode? If so, it looks like it’s just very out of focus.

I had a lot of power on, really in line mode I had to make a stroke and I don’t know why it doesn’t. In preview play it does it without stopping.
Another problem in the filling, does not complete the entire area, that is, the laser takes a long time to turn on, however if I run another program it makes me a fast and precise filling.

My guess is that the other program is using M3 mode, not M4, and your acceleration is really low, so it takes a while before the burn starts.

Try changing to using GRBL-M3 in LightBurn instead of GRBL, and see if the result is closer to the other program. You could post your settings here as well, which would help. Type $$ in the console and press enter, and copy the resulting text here so I can see.

I leave my grbl configuration. it is possible that there are changes in it of a standard machine, since my machine has a not very light Chinese mechanics. the endstop are optical and that is why they are with inverted logic, in that I have no problem. I have a few hours of travel and I will arrive at the machine to check the GRBL-M3, I am using a PWM configuration, using the maximum limit of $ 30 = 420 to not exceed 15mA and not damage the CO2 tube. But being the default values ​​also made me the same problem. Thank you very much and hopefully we all solve it and help more people.

Sorry, but I am not understanding what “problem” you are identifying. If you would, please explain using different words.

Sorry, I use the translator and spelling mistakes get complicated in translation.
The configuration I have of GRBL, in laserGRBL for example makes a quick fill using a gcode saved from LB and without overexploration, however with LB I can do the same filling but it needs overexploration to do the same. Later I take some photos or videos if they can be uploaded. I think it will be better understood.

Thank you, that will be helpful. You can also just use your native language to express what the issue is and we can do the translation here.

Hi. It seems that making some changes in the programming of GRBL, especially changing accelerations. And by setting the GRBL-M3 mode the laser behaves properly. I still need to set the minimum de potencia, ya que al 10% no llega a grabar, pero eso ya es poca cosaof power, since 10% do not get to record, but that is already a small thing. I thank you very much for your help. I leave a picture of a scale made again.


En los bordes me quema mucho y creo que haOn the edges it burns me a lot and I think there is an adjustment to evOn the edges it burns me a lot and I think there is an adjustment to avoid this, does it have to be mandatory to use overexploration? Really, thank you very much for your help.

GRBL-M3 mode leaves the power on at a fixed (constant) value. GRBL (M4 mode) uses variable power as the speed of the laser head changes, but laser power isn’t linear, so this is better, but not perfect.

Overscan is necessary to avoid the dark burn at the sides, even when using the variable power mode, and much more necessary when using constant power mode (M3).

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