Problem with Lightburn or my understanding

Using a chart from Hurricane Lasers, I was trying to burn a 1" square through 1/2" Oak. I have a 100 watt laser, Chinese, with a Ruida 6442G controller.

I used 98 watts at 5 mm/sec per the chart. Barely etched a line in the Oak.

I then set the Ruida controller to 98% Power, 5 mm/s speed, Hit the pulse button at the same time I moved the laser with the arrow keys. A VERY satisfactory cut was done. So now I am puzzled. I know the laser should be able to cut 1/2" at one whack… why the discrepancy between what LightBurn does vs my hand moves. Shouldn’t they be the same??? I don’t have dot mode, dash mode or override PWM mode set… Can someone guide me on this one?

What did you do to set the Watts of this cut? Maybe I am not reading this correctly.

98 watts. 98% x 100 watts == 98 watts cut. Speed 5 mm/s

I think I have a REAL REAL misunderstanding of what the Min and Max power do. On this cut, I had the Max power to 98% and the Min power to 10% ( Why??? ) Barely scratched the surface.

When I set the Max and Min power the same… to 95% … the cut proceeded to do it’s thing correctly. Now, I have been using LightBurn for over a year ( I think… ) Made many, many wood boxes and other things… how could I have “Lucked out” this long?? Very confused…

On a ruida controller, the controller defaults to the min power setting when going at or less than 10mm/s This is built in to the ruida firmware. My guess is that you have never run that slow before, so that would be why you are just noticing it now. :slight_smile:


There are a few things happening here. Grumpy is spot on. Ruida defaults to the value set in the Min Power for any cut set to a speed of 10mm/s or slower. So there is that, but there is also the understanding of min/max power usage.

For the vector cuts, Min and Max are used to ramp the power (up and down) based on acceleration/deceleration of the head. This allows greater control of the power deposited as your head slows for a direction change. Using a wide min/max “range” on this small size of cut does not allow time for the system to ramp and reach the max power value for long prior to starting the reverse ramp of power. If you set this range closer you can avoid over burning in the corners while still having enough power deposited to pierce the material.

Russ has 4 short videos that cover this in detail starting with this (#55 1-4 in the series):

And BTW, I really like the boxes. Very nice execution of inlay work. :slight_smile:


Yes, I watched his vid’s. And even he was 8 month’s into his before he realized what was going on. :slight_smile: I don’t feel too bad now… I was worried more that I had an issue with the machine… so thanks to all who answered. And thanks for the comment on my boxes… I do enjoy the collaboration between LightBurn, My Machine, and My ideas!

It shows. Please keep sharing. They are very much enjoyed!

Oddly enough, it was an email exchange between Russ and I that set him straight. :slight_smile: He went off and ran his laser through a digital oscilloscope to verify it. He’s not always right, but he’s very thorough, and a wonderful man. I have enjoyed watching his videos and usually learn from them.


On a similar subject, is the min power $31, used with a GRBL controller? I read that it is used for grey scale, but how about when dynamic laser control is used? will this always go down to 0 if required or only to the value of $31? I ask because of having problems at the end of higher speed vector engraves 10,000 mm/min where the line disappears 2mm from the end unless the power is above about 35%.

Sorry to hijack this thread!



In GRBL that’s not Min Power, if I understand correctly - it’s the lowest RPM your spindle will turn at when power is applied. So if you have a spindle that goes 5000 to 15000 RPM, those would be your $31 and $30 settings. They aren’t nearly as useful for a laser. I believe there’s a “min PWM value” setting that’s available, but only at compile time. I’ve been meaning to verify this.

Thanks Oz interesting to see what you find.



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