Hi, trying to find the beam width of this lens" Cloudray Compound Engraving Nozzle Set Focus Lens Diameter 18mm with Compound Lens for Laser Engraving Machine" It’s a 1.5 inch used on my 70watt c02. any help would be appreciated. relative newbee with c02.----Mike
That could be tough. It depends on what it’s cutting and the optics. I think what you are looking for is kerf? The cut diameter of the beam… But the compound lens is usually for engraving.
You can use a bitmap of known size and lase them such as dotSize.lbrn2.
Use the ‘zoom to frame’ as it’s pretty small. See if you can reproduce these dot they are 0.1mm.
If it is kerf, this is how I measure kerf.
Ten cuts then measure the gap and divide by 10.
Measures 1.64 so the kerf is 0.164 when you use it, it’ll usually be divided by 2 as you are cutting both sides.
Thanks I’ll give it a try. I’ve been using lightburn to make 3 parallel lines starting at .3 mm apart and reducing the distance by .01mm per run until space between disappears. Ended up with .2mm beam width. Thought with compound lens 1.5" it would be less.
What, may I ask are you trying to do? Just curious.
I rarely cut with my compound lens. I use it entirely for engraving.
Hey Jack,read an article on spot size or beam width then computing maximum dpi. I thought with a compound lens the 1.5 would be smaller than .2mm but nope.
Too bad… Mine usually turns in 0.1mm dots pretty well but it takes good procedures to make it happen.
What kind of material are you using?
Did you run the ‘dot size’?
Can you post any kind of results?
Are you sure your compound lens is focused?
Stock lens in my machine was 1.5".
Here’s Russ’ video RDWorks Learning Lab 137 Compound lens Facts and Fiction, might help… I think this is the right one, but didn’t have to re watch it… He appears to agree with you… 
He also has one call the ‘holy grail of dots’ that’s also pretty well done. Well, actually, he has about 200+ videos on happy (or unhappy) lasing.
thanks I’ll check Russ out I’ve seen some but need to re-watch