5.5W diode laser not cutting through 3mm mdf

I have a 5.5w diode blue laser but having difficulty cutting through 3mm mdf. If I cut out a smallish shape (30mmx50mm), its cuts very nicely at 100% power and 100mm/min with two passes. As soon as I have bigger jobs to cut, it doesn’t cut through most sections. As if it gets tired or something knowing its going to cut a big job. I have tested various speeds, power, heights (laser to material with all in focus), air assistance and not, and nothing is working. I have also noted that my horizontal lines cut better than my vertical lines.


You said you have tried with and without air assist - what do you have for air assist on the machine? You would need to be injecting a good amount of air directly into the cut for it to make much difference. Higher wattage diode lasers use multiple emitters in a linear array, so the beam is a rectangle, not a dot, which would explain why it cuts better in one direction.

If your machine has a working Z axis, you can try stepping the Z down a bit with each pass to set the focus deeper, and that can help too.

Could this be the diode overheating and losing power?

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I bought a Hailea 55L/min air pump with home made pipe and nozzle. The smaller pipe restricted the flow too much, so used a much thicker hose with plenty air coming through the nozzle. I tested the air assist with a small shape and thought this is making an amazing difference. I immediately tried the peacock and it didn’t make any difference in the end. I can try to inject the air flow into the cut a bit more to blow out more debris. Yes it does have Z travel and not making much of difference with regards to my problem. I have tried with and without z travel per pass. I wonder if I could have a power supply problem? Does the GRBL settings look in order? I have done a lot of testing and adjusting and this seems to work the best. The guy who built the machine, CNC router with the laser attachment, says I must look at the x and y acceleration ($120 &121) but this is cutting so slow I don’t think that’s the problem. I tried to adjust it up and down but wasn’t helping at all.

Check the S-Value Max setting in the Device Settings in LightBurn and make sure that matches the 255 you have set in the $30 parameter. Other than that, nothing jumps out as a possible issue.

Easel once adjusted the $30 paramater to 12 000 for the rpm on the router so I have encountered that problem before. Both are set to 255

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