I’ve got a fair sized shop compressor that I’d like to use as a source for air assist on an ortur Lm3.
I’m planning to give the air assist its own dedicated feed with a pressure regulator just for the LM3 so I don’t have to keep changing the supply around.
Presuming that I’m mainly going to be making parts and scenery for models, and cutting 1-3mm ply or balsa, what would be the best “set and forget” psi to set my regulator to?
I think it depends on free air flow at the nozzle and not PSI at the regulator, and will be affected very much by the design of the air assist nozzle.
I’m using the factory default nozzle for the LM3. No modifications.
I obviously don’t want to just crank thing up to the maximum, I’ve got no way of determining the air flow, only the psi at the regulator.
It’s a large shop compressor with a large tank that was originally purchased for high pressure spraying. If I just leave it at maximum it will could possibly damage the laser engraver, or at least blow the materials that I’m trying to cut out of alignment.
The answer to your question is; “It depends”. There is no single “correct” amount of airflow for air assist.
I would set up a series of test cuts at different materials, depths, speeds etc.
Start at low pressures and work your way up.
Maybe I should just have asked “what psi does the official Ortur air assist use”? .
You could ask Orturs support that question but I think you are searching for precision where there is none.
In my experience, the amount of airflow depends on the conditions at/in the cut. Various materials, various cuts, at various speeds at various thicknesses, and at various airflows produce differing results.
The psi that is needed at your compressor for a particular cut dynamic depends on the design of your air assist head, connections, feed hose, and compressor. So it’s best to just experiment until you understand the characteristics of your air system.
How much would be too much?
I’m obviously not going to put 350 psi through it, but 10-20, or 1-2?
A common air assist pump is a Hailea pond pump or a clone. These are rated at 0.03Mpa, or 4psi. Ortur sell a pump which is apparently rated at ‘>= 0.003mpa’. The ‘m’ is probably an error and the number of zeros may be, too. And who knows what >= implies ?
I would start at 2psi and expect to increase it a little. You’re only trying to get the smoke away from the lens. If you can feel the stream of air with your finger, that’s probably sufficient.
We set ours anywhere from 12-20psi. If the parts blow around turn it down. Get a regulator with a moisture trap. Shop air can have unexpected moisture and water may damage your cuts.
It’s primarily used for paint, so it’s got all the bells and whistles.
I have a larger Chinese 50W. I have a 175lb compressor and I regulate it to 60psi when there is an active air assist on the layer, cutting most materials except acrylic. Every job, setup and machine are different. I know that’s probably an unreasonable pressure, but it works well for me… there is a wide range of acceptable values.
Generally the idea is cut with the most power and highest speed … what ever that may be for the material.
Unfortunately you will have to follow @donkjr suggestion, as I agree … just like the rest of us have done… 
Think about what is happening to the material and will higher or lower air pressure make a difference.
If you make multiple passes that would also have to be taken into consideration. How the air strikes the area also has an effect.
Good luck…
