For those with 50 watt chinese lasers

You don’t say what you speed was but the ruida control drops down to the min setting if the speed drops below 10mm / sec. So you might have been always cutting at what ever you min pwr was.

I tried it out on the 3mm and it worked perfectly for me. Thanks!

Well I think I finally got the thing running correctly. Besides the lens being in backwards, the airline was pinched off inside the machine. After I fixed that it made a big difference. Started cutting through roughly along the parameters that were stated here. I want to thank everyone for their responses. I’m sure I’ll have many more questions in the days to come.


1 Like


Interesting about the lens. I was curious about “which way is up” and have tried a 2" plano convex lens both ways. It seems to change the focal distance slightly, but I really can’t tell a tremendous difference between curved side up and curved side down. The experts mostly seem to say convex side up / flat side down, so that’s what I do.

But that leads to another question… What is the focal length of your lens?
I almost always cut wood or acrylic 3mm or greater with a 2-1/2" or 3" lens. I get better results than with a short focal length lens like 1-1/2"

And, oh hell yeah on the air assist. Lots of air makes a BIG difference. I usually run 20-30 PSI when cutting wood. The more the merrier…

Mine is standard 50mm lens, which in my setup puts the nozzle tip about 4.5mm above the work piece.
Lens is flat side down towards the tip.



@DavidF what kind of nozzle do you have?

I cut 3mm @ 11mm/s 35 % power 1 pass. But with air compressor @ 25-30 psi.

First of all, the Chinese laser cutters all need a $5 milliAmp meter installed if it doesn’t have one. In general, you can’t trust the display to set the power level safely. Too many have said they set their machines to 50% and it used to cut but only a year later and it no longer cuts. And then we tell them that lots of times, anything over 40% is over 25mA power and it’s too much for the tubes they ship with the machines. Over driving them kills them fast.

With a cheap $5 mlliAmp meter you can be sure what your power level really is.

As for the mirrors, look through the FAQ at the K40 Laser site. Gobbs of excellent information and it even talks about the milli Amp meters.


1 Like

Hi Enno, who was this question aimed at?



You must have a very good tube. My original tube is down to about 95%power and 5mm/s to cut 1/8’ baltic birch and won’t cut anything thicker. I need to get a new tube soon.

I cut 3/16 with 3 speed and 39% power I am cutting with a true 60 watt tube. 1 pass

@ Enno I have this one: