Top of focus lens always dirty

It seems that the top of my focus lens is always getting dirty, fast. Has anyone set up a 2nd air line to give some positive pressure above the lens? Or is this due to insufficient airflow/exhaust inside the laser? I can clearly see the smoke getting taken out the back (after I moved the exhaust), but it does linger a little bit on larger engravings.

My exhaust line is long, maybe 35’ of 6" duct with a 6" inline fan. Anyone think that a fume coffin would help/boost the exhaust?

Sorry if I posted this in the wrong place!

Thanks in advance!

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I also have a standard 60 Watt OMT machine with 2 small air compressors connected to the nozzle. I have never experienced the problem you describe, it almost sounds like you have “false air” in the nozzle, a kind of injection.

How does the debris get into the tube to be on top of the lens? Must not have good ventilation…


That’s what I was assuming was the issue; just too much ducting. I don’t really have another option, short of renting a lift to install a 2nd inline fan. I might have to add a 2nd air line just to help keep it clean until I can figure out another solution. Ugh.


I have an upgraded head where everything is pretty much ‘open’ and I don’t have this problem…

I do leave the ‘lid’ open about an inch when I need ventilation…


I can’t really open the lid when engraving, I lose too much airflow and the smoke hangs out in the laser. Leaving it open about 1/4" seems to give me the best airflow.

I think the only option I have is to get a lift and install a 2nd inline fan. Until then, I guess I’ll just really keep on top of cleaning the lens.

Thanks for the input, as always!

I’m personally a much bigger fan pun intended of blower-style fans as opposed to in-line ones. I have a similar run, but with a big blower instead, and have no issues. With that said, my focal tube mount block provides more enclosure from the ambient air than the example photos in this thread.

Didn’t even think about a blower… Do you have specs on the one you use? (size, power, cfm, etc). I’d much rather get one of those than deal with trying to get another inline fan up there! :slight_smile:

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Im fairly certain this is the exact model I have:

A word of warning: You absolutely MUST clean the mesh on the intake side every 6-12 months. It packs up with vaporized material and you will lose suction progressively. Depends on how much and what you’re cutting, obviously.

Awesome. Thanks!

I hope you get a quiet one. The ones I’ve heard are so noisy you can’t think…

It is still an inline fan…

Good luck


Yep. Noisy-as, but I put mine on the other side of a wall and the performance is well worth it. I have a pair of Sony WH-1000XM4’s that completely eliminate the drone, good for those 10 hour workdays.

The fix is stick something louder in your ear? :crazy_face:


They use ANC - Active Noise Cancelling. It works by playing the opposite sine wave to the sound that’s noisy in the environment, effectively cancelling it out (destructive interference) Noise-cancelling headphones - Wikipedia

So, they’re not louder, just the opposite wave.

I ended up using a Wen dust collection blower we had laying around, similar to this one:


Works very well, has no problem pushing air through all 25+’ feet of duct, and isn’t too loud! (Kinda like a leaf blower that’s next door.)

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