Extract to Atmosphere for a Laser Cutter

In an earlier article we discussed two main types of laser fume extraction for a laser cutting machine one of which was laser fume filtration and the other Extract to Atmosphere (ETA). Here in this article we take a more detailed look at the correct design of an extract to atmosphere system.

This is a highly specialised subject. Most laser cutting machine and laser engraving machine suppliers as well as many fume extraction suppliers do not truly understand what is required to provide for an efficient, well performing extract to atmosphere set-up for a laser cutting machine.

By some standards ETA is merely a small turbine with enough flexi-hose to hang out of the nearest window. Nothing could be further from the truth or in fact nothing could be more inadequate and potentially dangerous than this type of set-up.

For an ETA system to perform well and most importantly for it to be safe, the contaminated air within the laser cutting machine must be quickly removed and expelled well beyond roof height where it will quickly dissipate into the atmosphere safely.

This requires moving very large volumes of air, a by-product of which is the generation of high levels of noise. This is the main reason why some sites, such as those in inner cities, simply are not suitable for ETA.

Start at the laser machine by connecting a 1m flexible hose from the extraction port to some kind of gate. The gate will be used to control flow as well as shut-off the machine from cold/damp air that may enter from outside when the system is not in use.

The type of flexible hose is critical; under no circumstances use cloth or foil types of flexi hose as these are designed for very low pressure extraction, such as tumble-dryers, and they will collapse and perforate.

The only type of flexi hose to use is made from PU, sometimes treated to be ant-static and with very strong reinforcing wires. Use a transparent version as you can then monitor the level of contamination and change it when necessary

After the gate the duct must be made from galvanised steel with at least 150mm diameter. At each join it must be riveted and sealed using a suitable mastic. This duct will widen to match the diameter of the fan inlet. From the fan it will be a constant diameter to match the fan outlet.

The fan MUST be positioned OUTSIDE of the building so that the duct from the laser cutter is under vacuum. This is safer because if the duct is compromised fumes will not escape from it into the work environment. If circumstances allow, site the fan on the floor as it will be easier to service.

The performance of the fan is critical to the efficiency of the machine and should be specified by a professional making careful calculations for the size of the laser machine and the length/design/resistance of the duct.

To reduce noise, just before and just after the fan fit a pair of attenuators. These act similar to the baffle box on a car exhaust.

Beyond the fan outlet attenuator the duct should run in a straight line upwards to a point 1m beyond the roof line or apex of the building. The duct should terminate with a jet cowl and NOT any other type of duct cap.

Careful consideration should be given to the discharge point to allow for maximum dissipation of the expelled air and minimal nuisance to neighbours.

This type of set-up will provide for many, many years of use with next to no deterioration in performance and little to no required maintenance.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions and can supply custom designed ETA solutions. Our experts would be happy to advise you which configuration would suit your application best.