Questions about air assist

I am about to hook up an air compressor to my 60W CO2 laser (manual connection, bypassing connection to the controller).

  1. The micro air pump that came with the machine puts out approximately 5psi? I have found no formula to convert CFPM to PSI.

  2. It is better to have the air blowing from outside of the cone as opposed to thru the cone. That does not make sense to me, maybe if the laser always traveled in one direction that could be true.

The reason for an external air supply is that (according to my readings) different materials cut/engrave better at different air pressures. I can only find general information about this. Plexi cuts well at 5psi but engraves well at 35psi. Wood, which is a broad generality, cuts better at 10psi. Nothing about engraving wood at any psi. I have yet to play with any high grade stone, ceramic tile or coated metal.

So my question is: Has anyone produced a chart on the general characteristics of air pressure on various materials, cut and engraved?

I’m 7 months into my laser and still learning/observing. Any advise would be welcomed.

Thank you,


Engraving doesn’t care about air assist in my experience. I have the air assist off and only the minimal bypass during engraving to keep the lens clear.

Cutting practically demands unrestricted air assist, and it should be down through the nozzle, which is in turn down close to the work surface. Less than 10mm, preferably down around 5 - 8mm. I use 5 psi flow pressure through a Cloudray No3 nozzle for acrylic, and bump it to 15 psi flow pressure for Premium MDF and clear pine.

The air assist is to clear the out gasses from the cut as the laser works, hence the straight down in need. From the side only works properly in one or two directions.

Question, do you know the difference between an engraving set up and a cutting set up?

Let me restate that.
I initially played with engraving at first, using the various settings: dither, grayscale, newsprint, etc.
I have ben more centered on cutting and using LINE for scroll work.
I have a couple of ideas that require engravings.
I have the feeling that you mean something else by SET UP.

I have to admit that I do not.

Correct. There is a physical difference between an engraving set up and a cutting set up. It’s all below the #3 mirror and your air compressor.

An engraving set up has a restricted air fitting to a nozzle with a relatively large opening that the focal point is around 20mm below the tip. For engraving, the exhaust is doing most of the work, the air assist keeps the lens clean and gives a few puffs to the work.

A cutting set up has a wide open air fitting to a nozzle withe a smaller opening. The lens is held further up in the lens tube putting the high air flow through a small opening down close tot he work and into the cut keeping the out gasses clear. High air flow is not something the little air compressor that came with your machine can do. We’re talking somewhere in the neighborhood of a 5 or 6 gallon tank and compressor. I have a feed from my big shop compressor in the next building, It’s 120 psi so I have a regulator and buffer tank in the laser shed to knock it down to 60m psi before it goes to the regulators at the laser.\

And it doesn’t matter the focal length lens I have in. 1.5" all the way up to 4", the tip to work distance only varies by less than 2mm.

If I need to engrave, raster ( fill ), or vector ( line ), I simply turn the air assist off so only the minimal bypass is on keeping the lens clear. That is also assuming you have good laminar air flow across your work. I had to move my exhaust to get that part right as well. Mine shipped with in the front and out the side. That does NOT work. It now exhausts out the back.

You can see the physical difference in the nozzles on my Google Mod page at the top, and Air Assist 04 shows the stark difference switching from an engraving set up with bad air assist to a cutting set up with good air assist can make. There are also some sample pics at the bottom.