I know this isn’t an exact science…
Jack, you said something about your distance from nozzle with a 2.5" lens on the Omtech. What did you finally set yours. I have my new lens and lens tube installed. I set it at 10.5mm, speed 25mm/sec, 35Max and 35Min. Still burning the edges more than I want.Ideas?
As much as I try to get a better focus, I can’t do any better than this chart… Not sure what lens combo you are using. I do ramp tests on all of them to ensure they are the best I can do. I leave them tube/nozzle so I can just put them in. I find little variance, usually from a ‘knot head installation’ somewhere with the lens…
I haven’t run the 4" lens kerf test, configured for cutting, but I can see it’s relatively large.
I guess it’s pick your poison… 
The 10.5mm was what I got with the ramp test. Your chart shows 5.6mm. That would cut with one pass. Do you do more than one pass?
I pretty much don’t do material that I have to make multiple passes. Always seem to be a very rough edge or at least burn like…
I’ve been meaning to use the 4" on my kerf testing template to see how close it is to what’s in the diagram.
Take a good look and make sure the diagram has the lens mounted in the correct position and you have the right nozzle.
Can’t tell you how many times I’ve confused this… That’s why they stay ‘pre configured’ to just put in and attach the air…
My new nozzle has the lens glued in???
Bummer… Never seen that ‘tact’ before…
I guess you’re going to have to go with whatever the ramp test gives you.
How do you run a kerf test?
kerf-master-00.lbrn2 (71.4 KB)
Yeah, many of the manufacturers want you married to their lens tubes so they glue them in. Measure the OD of your lower tube, there’s a good chance there is a generic replacement that will let you swap / move lens’ easily. I use the Cloudray C series ( the E series is the same but a different OD ) that lets me put anything from a 1.5" to a 4" in the same tube just by changing the mounting positions.
As to focal lengths. I discovered with my PVD lens’ that a low power line was a bit off from my full power cutting focus. I have Russ’ focus test ramp, and just made some 3mm MDF versions that hang over the side letting me test cut full power.
American Photonics is adamant that ZnSe optics should be glued in place, rather than using mechanical compression. They show what happens if you tighten the nylon screws on a beam combiner:
But I don’t think there’s a lot to putting in a lens with a soft silicone O-ring. They do glue lenses in the tube.
It’s not a big deal to replace a glued lens. I get a PET (polyethylene terephthalate) cup or wide-mount container, spray in a little carb cleaner, let it soak for awhile, and the epoxy will dissolve. Then just get little tubes of 5 min epoxy, mix it correctly, dab and spread a small amount with a fine tool like a toothpick or plastic spudger, and drop the lens in.
I prefer to put down a sheet of paper and burn a series of parallel lines like 0.5mm down to 0.2mm apart, at low power.
When it’s out of focus, the kerf widens and the lines merge. Pretty clear to read. With a series of lines of different spacing, you can see just how out of focus it is.
However, if you have the beam speed/power down to the bare minimum to burn paper, then when it goes out of focus rather than widening the burn it may just not burn at all, which may be confusing at first
This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.