Air assist for lasers: airflow, pump and how to use it
are explained briefly when you hover over or tap them.
Air assist is a jet of air that blows through a nozzle on the laser head straight onto the laser spot. It looks unremarkable, but when cutting it often decides whether the edge comes out clean or charred. Here you will find out what the air does, how much you need and when less is better.
What air assist does
Lasering vaporises and burns material. This produces smoke, sparks and sometimes small flames. The air jet helps in several ways:
- Suppressing flames: The air blows out small flames at the cutting point before they grow. It does not replace supervision or a fire extinguisher, though.
- Pushing smoke out of the cut: Smoke in the kerf absorbs laser light. If it is blown away, more energy reaches the material.
- Protecting the lens: The airflow keeps smoke and resin away from the lens. A dirty lens loses power and can be damaged by heat.
- Cleaner edges: Fewer embers in the cut means fewer dark edges. More on this under Burn marks.
- Deeper cuts: Because the kerf stays clear, you can often cut thicker material with the same settings or need fewer passes.
Without air assist, clean cuts in wood are hard to achieve with many diode lasers. If a cut does not go through, missing or weak air is one of the first causes, see Does not cut through.
How much air you need
Manufacturers usually state the airflow in litres per minute (l/min), sometimes with the pressure in kPa as well. A few examples from manufacturer information:
| Example | Specification |
|---|---|
| Pump on the Acmer P2 33W | 30 l/min according to the product page, the FAQ states 25 l/min |
| Air assist set for xTool S1 | at least 30 l/min |
| Kit for the Atomstack X70 Max | adjustable from 0 to 60 l/min |
| built-in pump on the CO₂ laser xTool P2S | two-cylinder pump with 200 kPa |
For diode lasers up to about 40 W, the supplied pumps are usually in the range of 20 to 30 l/min, and some kits go higher. That is enough for most cuts in wood and opaque acrylic. More air helps a little when cutting thicker materials, but the effect gets smaller. It is also decisive that the nozzle is narrow enough and sits close to the material. A thick hose with plenty of air that disperses widely does less than a focused jet.
Less air when engraving
When cutting, the rule is full air. Engraving is different. Too much air swirls the smoke across the surface, and resin settles as a haze around the engraving. In addition, a strong airflow cools the surface, so the engraving gets lighter and you need more power.
Machines with two air levels separate the two explicitly. Thunder Laser, for example, describes a cutting mode with a stronger airflow and an engraving mode with a weaker, even one. With simple pumps you adjust it with a dial or in the software.
A good rule of thumb to start with:
- Cutting: air assist at full
- Fill engraving on wood: little air or off, extraction on
- Fine lines and lettering: little air, so the smoke does not drift across the engraving
- Slate, stone, coated metal: usually little air, since hardly any flames occur
The best way to test this is with a material test: the same grid once with and once without air.
Control via software
In LightBurn there is an Air Assist switch for each layer. On GRBL machines you set in the device settings whether the pump is switched on with the command M7 or M8. According to the LightBurn documentation, the switch only works if the machine has controllable air assist. If the pump has to be switched on by hand, nothing happens via the software. Many manufacturer programs switch the air automatically depending on the type of job.
This way you can run the engraving layer without air and the cutting layer with air in one project.
Aquarium pump or compressor
There are three common air sources for air assist:
| Air source | Typical data | Notes |
|---|---|---|
| supplied laser pump | 20 to 60 l/min | usually fits directly, often controllable via software |
| piston or diaphragm pump from aquarium and pond supplies | e.g. approx. 35 l/min at 18 W | cheap, suitable for continuous running, check connection and pressure beforehand |
| workshop compressor with tank | high pressure, depending on model | plenty of reserve, but loud, needs a pressure regulator and water separator |
Aquarium and pond pumps are built for continuous operation. That suits long laser jobs. Their pressure is limited, though. With narrow nozzles, less air arrives than the rating plate says.
A compressor delivers more pressure but brings its own problems. It switches on cyclically, is loud, and the air can contain water and, with oiled models, oil. Oil mist on the lens is bad. If you use a compressor, a pressure regulator and a water and oil separator belong in between. Also check how much pressure the nozzle and the hoses on the laser head can take.
Noise
The pump runs during the whole job, so for long engravings it runs for hours. Noise therefore matters, especially in a flat.
- Small air assist pumps are sometimes advertised with values around 40 dB. Under load they are often louder.
- According to a comparison on heimwerker.de, normal compressors are at about 70 to 100 dB, so-called silent compressors at 30 to 65 dB depending on output.
A pump on a soft mat or in an insulated box is audibly quieter. The box needs ventilation openings, though, otherwise the pump gets too warm.
Retrofitting
If your machine has no air assist, there is often a suitable set from the manufacturer. For open diode lasers it usually consists of a nozzle that fits over the lens, a hose and a pump. Pay attention to these points:
- Suitable nozzle: It must fit the laser module and sit centrally over the beam. A crooked nozzle blows past the spot.
- Check the focus distance: A new nozzle can change the distance to the material. Then set the focus again, see Laser focus.
- Hose routing: The hose must not catch while the head moves or get into the beam.
- Control: If the mainboard has a connection for air assist, the software can switch the pump. Otherwise it runs by hand.
Not every machine can be retrofitted. On the xTool M2, for example, the pump is built in permanently and there is no connection for an external air source.
Keeping the nozzle clean
The nozzle sits directly above the smoke. Resin and soot settle inside and narrow the air channel. Then the air blows at an angle or more weakly.
- Remove the nozzle regularly and clean the inside with a cotton bud and a little isopropyl alcohol
- Check that the opening is round and clear
- Inspect the lens while you are at it
- Check the hose for kinks and cracks
Continue with: Burn marks, Material test and Laser accessories.