Grbl-lcp and raster photo settings problem with laserweb

Hello everyone! I am not an expert and I am now starting to engrave with the laser. I have been following you for a while and thanks to you, I updated the k40 control board with an mks sbase 1.3. I connected pin 2.5 (-) to L and use an additional power supply to power the board and motors. I kept the pot and the fire test button, installed the firmware and left the default grbl-lpc settings. I am starting to use Laserweb but I have noticed that I cannot exceed a speed of 12000/14000 axis maximum rate because my axes freeze. With other programs I don’t even get to 10000. but that’s not really a problem, 12000 is okay too. My problem is being able to take a grayscale photo on a piece of wood. I made several attempts and failed to obtain the result. I use a laserweb setting of 5% power and 12000 on 3mm mdf and every test I do I don’t get a decent result. I repeat I am really a beginner but as I understand it, I believe that the pwm cannot regulate with such a low power. I also tried to change the brightness through the raster laser but the result is worse. Can anyone help me or pass me a tutorial to be able to take a grayscale photo? The photo is 10x15cm I tried both with resolution at 96dpi and 300dpi both with color and in b / w through photoshop. Now I also have the doubt that I also have to connect the laser power supply pwm where the potentiometer is now?

Can you post a picture of what you get when engraving?

Theoretically the energy that gets on the object is a function of power and speed. But wood needs some time to get brown, which limits the maximum speed. If you drive faster and compensate with more power, you just get deeper grooves but less brown surface.

The PWM frequency has an equal effect. A lower frequency can make darker engraving and a higher frequency is better for cutting. I made a big test series and found a good middle value of 5000 Hz (at the L pin). Below was better for grayscale engraving and higher was better for cutting.

To get the correct dpi you can measure the size of the smalles dot you can produce with a specific power. Usualy this is around 0.1-0.2mm. A dot (pixel) size of 0.1mm would mean 254dpi. So scale your JPG to 254dpi and set the “tool size” in LW to 0.1mm.

You don’t need to change the connections to the LPS. It’s absolutely fine to have the pot at the IN pin and PWM on the L pin.

thanks for the answer this is the last attempt I made. 12000 mm / s
5% jpg 300dpi grayscale laser power via photoshop. So I try to change the dpi and change the tool size to 0.1mm? what speed and power?

the original photo is this.

as for the maximum speed is it normal that I cannot exceed 14000mm / s?

Are you sure you are talking about mm/s? 14000mm/s is 14 meter per second!!
I don’t belief that your machine can go so fast and as I explained, the wood needs some time to get dark.

I suggest to to try it with only 100-200mm/s with low power and see what you get.

sorry I meant mm / m. In the configuration of grbl-lpc the maximum speed of the axis 24000 is not in mm / m? on the LW (cutting speed) it is in mm / m so 200 mm / s is equal to 12000 mm / m is like the test I did. now I will try to lower the speed. Thank you

What is the power set to on the laser (not the software)?

on the laser with the potentiometer I set it to 18mA which should be 100% so as not to damage the laser tube.

You are trying to do raster pictures way too fast and hot. You need to slow down and lower your power. It is all about the quality. A good raster picture will take time to do. It is not like etching. I would suggest searching for some tips on how to get quality raster pictures on wood. There are a lot of opinions and tutorials. The way you process your picture will also have an effect on the outcome. Be patient and play. It is the best way to learn and get to know your hardware.

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the problem now is not so much the quality and that I can not make a grayscale … I tried to do as written on the LW documentation. I downloaded the calibration image which is this.
and I also did various focus tests. but I get horrible results.

I tried again to take a piece of photo with these settings.
Looking at the analog ammeter setting also high power it seems that the pwm does not work.
I also use a 7w diode laser with another program and can take raster photos. with the other program, however, using grbl-lpc with k40 mi the axes are blocked.

From your pictures I would say that your laser is not focussed correctly (washed contours). Try to adjust the focus. This can have a big influence to the raster quality.

Also, lower the potentiometer, not the software power! If you lower the maximum power in LaserWeb, you reduce grayscale resolution (count of steps), if you do it with the pot, all the steps from 0 to 100% can be used.


Thank you very much! the situation has improved but I still have problems with the intensity keep trying. Another question but if I wanted to have a potentiometer where I adjust the power and manage the pwm from the mks base how could I do? I have a 15w (7 real) diode laser controlled by the pwm.

In grbl-LPC you can only change the PWM frequency with a $ setting, not with a pot.