This could be a long one. First off, check my Google Mod Page. the first few pics are on the air assist.
I took Russ’ Ultimate Air Assist that is sold on Cloudray, and modified if for my situation. The first little set up was using the little compressor that came with the machine to switch it on and off by layer via the WIND terminal. Crude, but effective. The second version came about when I hooked to my 120 gallon compressor in the next building, with a dash of forgetting to change the pressure when switching between acrylic and MDF.
My current configuration consists of three solenoids and an ice maker shut off valve. Because I’m hooked to the big compressor next door, I had to be able to shut off the air completely, or the compressor would cycle a couple of times a night unnecessarily. The first solenoid is hooked to the STATUS terminal and only turns air on when actual cutting operations are in progress.
The ice maker valve is in a bypass hook up and is barely cracked for engraving air flow. Just enough to make bubbles in a cup of water. The last two solenoids are selected via a switch and connected to the WIND terminal for low and high pressure for acrylic and MDF respectively. In addition I have an over ride switch to open the air flow for manual firing and testing. With a Ruida controller, you can press and hold the pulse and arrow movement and manually run a line to cut material if you want.
If you go this route, take note of the solenoid pictured. You can use others for a higher incoming pressure. I have 120 psi coming in from the shop, and have it reduced to 60 psi at a little air bubble I use as a buffer before sending it off to the laser solenoid panel. But if you have problems with your big compressor and have to switch back to your little one temporarily, the solenoid pictured is the only one I know of that will switch with 0 pressure. Most air solenoids need a minimum pressure to activate. Also note that valve is available with three different fittings for different parts of the world. Make sure you order the correct one. And don’t forget the diodes!
Engraving vs cutting set ups. Almost every sub 100W machine delivers with an engraving set up. The new ones even have a little thing that looks like a can of hair spray they call a built in compressor. The ONLY thing that machine can do properly is engrave.
On the air assist side of the equation, engraving is wimpy. The head is moving fast enough to not care about out gasses. Some decent exhaust air flow, hopefully but not necessarily in the right direction, and enough air flow through the nozzle to keep the lens clear and it’s happy as a pig in slop.
Cutting, now he’s a picky bugger. He want’s a clear path to the material to work. He want’s good air flow down into and through the cut like a torch in metal would. This is where the cutting vs engraving get separated.
In addition to saving a few dollars on a wimpy air compressor, the manufacturers save a few tenths of a cent in the head configuration. Most sub 100W machines are shipped with a head configuration that holds the lens low, and the nozzle there for must be up away from the surface of the work. Usually in the 20mm range give or take. Then they put a restricted air fitting on the nozzle to go along with the little compressor. You get air, but not a lot, down into the cut.
A cutting set up holds the lens up in the nozzle or tube so that the tip is down close to the work and is fed by a wide open air fitting. In my configuration, doesn’t matter if I have a 1.5" or a 4" lens in, my nozzle tip is down around 8mm from the work surface. Russ likes to get his down around 3mm, but he’s working mainly with acrylic. For my MDF work I keep it up a bit to greatly reduce the resin halo around the nozzle tip. If I happen to be cutting some 1x8 clear pine, I change the configuration to get it down close for maximum air penetration. With proper air, I can cut 1x8 clear pine in 4 - 6 passes with only an 80W machine. I’m hoping Russ compound cutting configuration will reduce those number of passes even more.
You can engrave with a cutting set up just fine, just reduce your air flow or use the bypass valve. For cutting with an engraving set up, you are at a rough 40% disadvantage before you even open the crate. My best analogy to date is that cutting with an engraving set up is like driving at night in heavy fog with your high beams on. Get some good air assist down close to clear the out gasses ( fog ) then everybody is happy. You and I can’t see the out gasses, but it wreaks havoc with a laser beam.
Hope that clears things up a bit.