Laser Extraction

What is a Laser and how does it work?

The word laser is an acronym that stands for “Light Amplification by the Stimulated Emission of Radiation”. In this sense “light” does not only mean visible light but also includes electromagnetic radiation of any frequency – hence why you hear lasers referred to as an X-Ray laser, infra-red laser etc.

The process in which a laser is generated is fairly complex but in simple terms a laser is generated when the electrons in atoms in special glasses, crystals or gases adsorb energy. Usually an electrical current or another laser is used to make this energy. When the electrons adsorb this energy, they become “excited”. These “excited” electrons move from a lower-energy orbit around the atom’s nucleus to a higher-energy orbit. When they return to their normal state (often referred to as the Ground State) the electrons give off photons – more commonly known as light.

Ordinary visible light is made up of multiple wave lengths and is said to be “not coherent”. The peaks and troughs in the light’s waves are all out of alignment with each other which gives us the different colours – blue light, red light etc that combine to make normal light.

Light emitted by a laser has wavelengths that are all exactly the same wave length and are “coherent” – hence why the laser is one colour (usually Red). Unlike normally light from something like a torch (which is diffused light), lasers are a focused band of directional light.

Components of a Laser

How does a laser cut?

Laser beams in cutters/ engravers etc. are focused to a very narrow beam by a focusing lens in the laser focusing head. The focusing lens is made in such a way that the laser beam is perfectly round and the energy density is consistent. By focusing the beam on a single point, the heat at the point is extreme. This very high level of heat results in the rapid heating, melting and either complete or partial vaporizing of the material.

Using a laser hot enough and stable enough is vital in ensuring a clean cut and reducing the amount of LGAC’s produced.

Why do you need extraction of LGAC?

LGAC’s are also often referred to simply as a laser fume. When ever something is burned it gives of a fume. A great example of this is smoke. These fumes are fully of tiny vaporised solid particulates of the material you are cutting that has condensed into a visible fume. This fume will also include gases and vapours from the control gases in the laser cutting head, the oxygen burned around the laser and contact point and other gases that are released from the material when it is vaporized (wood gives of carbon dioxide when it is burned).

As we noted earlier a lot of dangerous chemicals have been found in laser cutter fumes. Breathing in toluene for example can cause irritation to the eyes and nose, dizziness, headaches, muscle fatigue, dermatitis, breathing difficulties and more. Toluene has also been linked to long term damage to the respiratory system, liver, kidneys, kidneys, eyes, skin and most horribly long-term exposure can cause difficulties in pregnancy and harm unborn children.

Ammonia, Carbon Monoxide, Styrene and many more have all been well documented to cause damage to your health – from small levels of exposure to long term exposure.

Then there are also the solid particulates to also consider. Breathing in some metal fumes can cause permanent lung damage, eye, throat and nose irritation or damage, pneumonia, metal fume fever and has even been linked to some forms of lung cancer (nickel).

Burning PVC gives of chlorine gas and has been linked to an increase in lung cancer with people exposed to PVC fumes. There is also debate about PVC being found to give off a measurable amount of dioxins – which are highly toxic – when burned ineffectively.

How do I extract LGAC’s?

Extracting laser fumes is very easy. Many laser cutters and engravers are either supplied with a dedicated extraction system with it or built into it. If the laser unit doesn’t then there usually always an extraction port to add your own.

A proper, dedicated laser fume extractor such as the BOFA AD350 or the BOFA AD Oracle iQ works by removing the fume contaminated air from the lasers enclosed chamber via the laser unit’s inbuilt extraction port with out disrupting the lasers stability or cooling the cutting point.

The inbuilt carbon filters on the extraction unit adsorb and filter the harmful gases and vapours in the fume and the HEPA particulate filter captures and filters the vaporized solid particulates (dust) in the fumes. The combined filter stages give a filter efficiency of 99.997% down to 0.3 microns (you can’t see below 30 microns and a human hair is around 100 microns). Many extraction units have options that allow them to connect to your laser extractor to turn on and off when you activate/ deactivate the laser cutter.

When extracting laser fumes, we also have to consider that laser do what they do by burning the materials at very high temperatures. This means we have to be aware when extracting laser fumes, we will also be drawing in larger particles of hot materials such as swarf or debris, especially when working with metals and wood.

If a smouldering ember is drawn in into the extraction there is a risk the air flow could fan the embers and either keeping them smouldering or ignite them fully. The smouldering or ignited embers could then end up sitting in the dry, combustible filter surrounded by air and more fuel. This could then ignite into a full-blown fire in the extraction unit.

Whilst the chances of this may be small if a fire does occur in an extractor it could be catastrophic and pose a significant risk to property, equipment and life.

It is always worth considering additional measures such as in-line filters like a spark trap filter (a box with metal mesh filters in that won’t burn and can deflect larger particles out of the air stream) or in-line pre-separator cyclones that also cause large particles to drop out of the air stream before they can reach the extractor. There are also in-line fire boxes that have pre-filters in an inbuilt fire suppression system.

Summary

LGAC’s can pose a significant risk to your health if not properly managed and controlled. Luckily it is very easy to remove this danger using proper dedicated laser fume extractors such as the BOFA AD range.

Make sure you are aware of the specific risks the materials you are working with pose. Check the MSDS sheets, be aware of what the airborne contaminates that are produced and the risks they pose as this can change the type of extraction system used. You should also consider the risk of ignition from hot embers and swarf which could get drawn into to the extraction unit.