Types of Air Assist for a Laser Cutter

Most laser cutting machines will incorporate some form of air or gas assist the function of which is three-fold:

• To improve the efficiency of the laser cutting process. Generally, this works by the positive air keeping vaporised debris away from the path of the beam in order that all of the laser energy is applied to the material.
• To improve the quality of output. This works by the positive air helping to keep vaporised debris away from the surface or the edge of the material being laser cut so that contamination of the material is minimal.
• To reduce the requirement for maintenance (cleaning) and prolongue the life of optical elements. This works by positively pressurising air at the focus carriage (the laser head) so that contaminants are kept off of the sensitive surfaces of the optical elements.

Well designed laser cutting machines will provide for all three of the above functions.

Some machines do not incorporate a nosecone. These are not good for laser cutting but are sometimes better for laser engraving because without the nosecone the laser head is lighter in weight, so it can move faster with lower vibration. If these machines have air assist then it’s usually delivered via a small bent metal tube delivered at an angle to the work surface at the focal point. The angled air assist helps to dislodge debris, pushing it into the flow of the extraction across the material surface.

It’s important to note that unless the laser fume extraction is very well specified then this type of directional air assist can cause premature contamination of the lens. At Lotus we do not favour this design of air assist.

For best results when laser cutting the laser head will incorporate a nosecone, which will sit a few millimetres away from the surface of the material. At the end of the nosecone will be a small hole through which both the beam and air assist are delivered. If the bore of the hole is too big and/or the distance of the nosecone from the material is too great then the whole process of air assist becomes very inefficient.

Nosecones with smaller holes work better as they direct the air more locally through the cut instead of around the cut. The smaller hole also helps to increase air pressure and allows for a smaller air pump to be used. In case where a gas is used instead of air, such as nitrogen for example, a small nosecone is essential to minimise the waste of a potentially expensive gas.

An often overlooked aspect to the design of air assist is the hose bore (diameter) through which the air flows from the pump to the nosecone. Many machines use a tube with a bore that is too small. This greatly reduces the volume of air that can flow through it.

Using a larger bore air assist delivery tube reduces the speed at which the motion system can run but greatly increases the efficiency of the air assist process. With some models of Lotus Laser Systems it’s common for customers that process high debris materials like laser cutting wood or laser cutting card for many hundreds of hours without the need to clean the optics. Conversely, many machines on the market with poor air assist designs will require almost daily cleaning of optical elements.

One important point to note is that when a nosecone is fitted air assist MUST always be used otherwise the process can work in reverse and the lens can quickly suffer contamination and even catastrophic failure.

Lastly, it is very important for the laser cutting machine to be able to activate the air assist through its control software.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions with a variety of air assist options. Our experts would be happy to advise you which configuration would suit your application best.