View Full Version : High-pressure air-assist query

Ian Stewart-Koster
01-07-2019, 8:46 AM
I've been cutting 18-20mm MDF with our big laser. It's yucky stuff, but the customer specified it.
The little aquariam pump air-assist really only keeps smoke away from the lenses, and has no fire extinguishing capabilities.

So I rigged up a separate air compressor and line coming down from the ceiling to the laser head - and rigged copper pipe through the now-defunct pen position/autofocus holder.

It served its purpose, and I got nice straight cuts and no under-burning, but of course, despite a water trap, there's still condensation in that line blowing as close as i could point it to the beam entry spot. That job took about 23 hours of laser time - 2 MDF sheets nested up tightly cut at 3 mm/sec- the job took a little over 3 days.

Really, I think I had too much air blowing, and want to rejig it with a finer copper pipe, and reduced air volume- but maintain pressure.

My question is instead of mounting it just beside the nozzle like I did, would it be ok to plumb it through the normal air nozzle insert, and out the nozzle?
I'm thinking the hole will be too big to get a nice pressurised jet of air- or am I wrong?

Thanks for any thoughts!

Patrick Gardner
01-07-2019, 10:57 AM
My machine has the air assist coming right out of the nozzle. I cut a lot of thick plex and must have high air pressure

Kev Williams
01-07-2019, 11:49 AM
simple answer is do what you want if it works!

My Gravograph machines both use a piece of copper tubing that can swivel out of the way if needed...

If you need a high-pressure nozzle, with a little fab work, one of these should work nicely-

Ian Stewart-Koster
01-08-2019, 5:09 AM
Thanks, Patrick and Kev.
I have some 3/16" OD copper pipe but I also have a few spare 0.9 and 1.0mm mig welder tips - great idea!

I was a bit against using the air-assist nozzle itself as its hole is bigger, so the volume of air needed to maintain pressure is much greater- the 3HP compressor would kick-in more often than I'd like...

Joe Pelonio
01-09-2019, 7:24 PM
I still the tubing from the pump to the laser exposed? If so, just use a “T”. They are available even with valves for fish tanks. I used one when I had an airbrush pump limited to 25 lbs. and needed to use a real compressor for some items. I could leave both compressors attached and just turn on the one I needed. The only tricky part was adapting the 3/8” fitting on the big compressor to the 1/4” tubing.

Ian Stewart-Koster
01-10-2019, 8:35 AM
Thanks, Joe - I did that on our Goldenlaser - added two Tees, so that incoming air could be from compressor or fishank air-assist, plus have an offshoot line to an air-duster gun to help put out fires, and I had two taps, so I could govern what air went where - but I had problems with condensation inside the nozzle, if the aircompressor was being used.
That nozzle is a great long skinny one - unlike anything I've seen since.
I didn't find it hugely successful running the high-pressure air in there - it ran out quickly - but the 5 mm hole in the nozzle might have been the reason.

I'm thinking of trying some 3/16" OD copper hydraulic brake line tube.

Kev Williams
01-10-2019, 11:53 AM
This spool of hose--
--is the type of air assist line Gravograph uses on their lasers, this particular spool was made circa 2004--

These are the hose markings, which are preceded by:
"FREEL IN-WADE COILHOSE FRE-THANE 95A PUR" (which I didn't notice till after I put together this pic ;) )
As you can see, it's 2.4mm ID with a 210 PSI pressure rating...

This is how my LS900 has been 'wired up' for the past 14 years-
-it's connected to my big 80 gallon compressor with a regulated 125 psi pressure. I can attest to its durability, and quickie fittings are available that fit--

This is my LS100, uses the same type hose, although 12 years or so newer and different markings it's essentially the same-
-Because this machine uses a swiveling bar(? not sure what else to call it) to actuate a remote auto-focus limit switch, there's no wires needed to travel the X axis, so no need for a wire chain. The air hose is all that moves with the laser head.

This is the laser head at full-right, note the hose is pretty tightly bent, but this stuff is extremely flexible, and best I can tell from what's feeding to and within my LS900, and the spool I'm holding, it will stay flexible indefinitely.

The only drawback with this hose is likely the need for high PSI to push air thru it fast enough... I'm thinking a diaphragm 'fish tank' air pump might not do it...

and FWIW, I have never once ever seen any wet come out of my 900's air assist line (but to be fair, I don't use it all that much!)

Ian Stewart-Koster
01-16-2019, 6:26 AM
Thanks a lot Bill.
We have 2 air compressors - a 2hp and a 3 cylinder 3hp one, and various Tees - some go to regulators and water traps, and some at full pressure, do not.
We have airlines piped all over the workshop. The unfiltered or unregulated lines often suffer from moisture in them.
I was using one of them - yes the fishtank grade 'air assist' is negligible, in comparison.
But I can see we don't need volume, as much as pressure.
I just wasn't sure if an aimed jet from fine copperpipe, beside the nozzle was as OK as coming through the nozzle, when the nozzle hole (1/4") is larger than the tube you show.

Rich Harman
01-16-2019, 2:29 PM
I use a Gast compressor, like what is used in gas station air filling stations. No tank. The compressor line goes into a tee, one side of the tee has a valve which controls how much air gets dumped, the other side of the tee goes to the laser and has a pressure gage. The more the valve is opened, the lower the pressure that goes to the laser. Close the valve and full pressure goes to the laser. Once in a great while there will be a couple drops of moisture, but it is very rare, and only when first starting up.

On the laser head I use a small metal tube next to the nozzle to direct the air. I prefer this because I like to use 1/2" thick magnets to hold things down and this allows plenty of clearance while nicely directing the air.