Laser won't burn on painted MDF

Laser not burning on my project. I’m trying to burn lines on my crib board. I have pre-painted the board via a spray bomb to the color white. I’m using a 3018 pro. I used Cut2d to design the project and Lightburn to burn the project. The laser works. I used it to burn lines on my template (cardboard) and I have used it to burn lines on MDF. I have set Grbl to $30=0 and $32=1. I have tried different settings in 112. $112=255 and $112=1000. No difference using either one. I have set Lightburn: speed 100; Max power 100. no difference. In device settings, I have set Lightburn at S-value max 255; and tried 1000. No difference. Is it the paint I’m using? The color I’m trying? Or is it the laser? The laser is a Sain Smart 5500mw, Wavelength 445. Thanks in advance.

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100 mm/minute, mm/sec, inches/min, inches/sec … ?

White paint can be extremely difficult to mark because it reflects most of the light from the diode, so it’s possible that’s the issue, but worth checking that you are using the correct speed units (mm/minute) and not something else.

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I started out at 300 mm/min, worked my way down to 100mm/se. Nothing. I was suspecting the paint. I’m not committed to white. I can always change to a grey that used before. I’ll see if anyone else chimes in with a solution. Thanks for your prompt reply.

you mean $30=1000, not 0 or your laser will never work

It has been working at that setting. I thought that setting was the min. That’s why I put it to zero. I’ll try 1000.

Just changed $30 to 1000. No difference!

no $30 is the max spindle speed and $31 is the min,
but when you try the cut, the laser ligths up? you see the beam?

Now you guys got me confused. I had $30 set at 1000 and $31 at 0. Beam is there. If I put a piece of cardboard on my work piece, it burns real nice.

I set $30=1000 and $31=1000. We have ignition. It is burning as it should! All is good so far.

You probably want to set $31=0 or else you’re going to have a bad time. This will probably force laser on during traversal moves and give you no ability to modulate power.

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I would be seriously looking at the paint rather than the laser not doing its job its a diode and diode lasers are not great at marking anything white as the wavelength is too easy reflected.

Go with grey if you can

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I just tried it at $31=1. It didn’t burn at all. Moved it back to 1000, and all is good. And your right, at 1000 the laser stays on while moving, but it does not cut!

Any reason you did $31=1? This really should be $31=0.

I suspect something else is at play.

Can you check the value of S Value Max in Device Settings? That should be set to 1000. If it’s not, set it to 1000.

Then $30=1000 and $31=0.

Please also confirm that $32=1.

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Yes, $32=1

I think I see why the laser is responding to the $31 number.

300 mm per minute (times) one minute per 60 seconds = 5 mm per second

If you moved to 100mm per second then you’re going way too fast.

100mm per second (times) 60 seconds per minute = 6000 mm per minute

My 3018 definitely requires a slower speed.

Open the Console window and type the following:
then press enter.

Copy and paste the whole report into a response here. I’m quite interested in the maximum speeds allowed and what speed you’re running your 3018 at.

Sorry. That was an error. It should read 100 mm/min!

I used much slower speeds than 100mm/min to engrave slate. There’s no harm in setting it slower until you get the results you want.

I’m not certain that we confirmed that the “S-value max” setting and the $30 setting were the same value from previous troubleshooting steps.

Lets have a look at all the settings:
In the Console window in LightBurn type the following:
then press enter.
Copy and paste that entire report in a reply here.

Then in the top row of LightBurn, click Edit, then way down the list to click Device Settings and capture that window with a screen capture tool so we can see that too.

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Ii don’t know much about settings but my experience has been color of the material makes a huge difference in the cut or fill. Try cutting/marking a local spot of black marker overtop the white paint and I am guessing you will see a huge difference.

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I agree with you. I will change colors. I did a previous board in grey and had no problems!

You could try putting blue painters tape over the area you want to burn and have the laser burn two layers at once. Or put blue painters tape on it and burn the tape away and paint a different color in that area for the design.

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