LASER CLEANING
Laser cleaning: Fast, cost- effective, resource-efficient
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A brief introduction to laser cleaning, the technologies involved, and the advantages it offers over other cleaning methods
What are the advantages of laser cleaning? Laser cleaning is a quiet, non- contact, non-abrasive, efficient, cost-effective, repeatable, high-precision and eco-friendly process that can be used to remove unwanted materials such as dirt, rust, paint, oil, oxides and other contaminants or impurities from surfaces. The process, which can be
used for micro-scale or large- scale cleaning of a number of materials, offers an attractive alternative to traditional industrial cleaning methods. These can often be labour- intensive or require the use of consumables, such as sand (sand-blasting techniques can also damage the underlying substrate) or hazardous chemical products/solvents (which then require costly disposal) depending on the material being removed. Laser cleaning, on the other
hand, requires no consumables – only power, making it more environmentally friendly and cost-effective than such traditional methods.
How does laser cleaning work? At its core laser cleaning involves an optical scanner
being used to move a focused laser beam over a surface. Here the beam interacts with any unwanted material, which absorbs the energy and rises rapidly in temperature until its ablation threshold is reached – the point at which its molecular bonds break. This causes particulates of the material to be ejected away from the substrate, or for the material to be vapourised entirely. The parameters of the laser beam – namely its power, wavelength, repetition rate, scanning speed and beam diameter – are carefully selected so that only the ablation threshold of the unwanted material is reached, rather than that of the substrate itself. This targeting of the right ablation threshold, combined with the fact that laser cleaning can be controlled with micrometre levels of precision,
“Laser cleaning is a quiet, non- contact, non- abrasive, efficient, cost-effective, repeatable, high- precision and eco- friendly process”
ensuring that the underlying substrate is left completely free from damage. The process can be
conducted either in person, using a handheld system to move the scanning beam over the workpiece – or remotely, delivering the beam to a laser head via an optical fibre, which
60 LASER SYSTEMS EUROPE THE 2023 GUIDE TO LASER SYSTEMS
can then be moved over the workpiece automatically using robots within an enclosure. To ensure user safety during
laser cleaning, a suitable fume extraction system must be positioned next to the process to ensure levels of harmful particulates that exceed government-set limits are not released into the air. Similarly, the user must also be protected in such a way that they are not being exposed to levels of laser radiation that exceed government-set limits. The simplest, most effective way of ensuring user safety during laser cleaning is to have the application take place remotely, within a strictly controlled laser safety enclosure.
What substrates and contaminants can be cleaned using a laser?
Metals Rust removal is one of the most common uses of laser cleaning, often done to ensure a clean, uncontaminated surface prior to welding or bonding applications. Rust removal is also performed to restore metal products or structures, for example those with historic significance. The most common metals that can rust include iron, cast iron, wrought iron and steel. For metals that don’t contain
iron – and therefore do not rust – laser cleaning can be used on those that instead develop an unwanted oxide coating. Such coatings can influence the integrity of a product, and are a sign that its surface material is breaking down. However,
removing the oxidation layer could expose it to further deterioration. This is where laser cleaning proves its advantage. Not only can it be used to remove the oxidation layer, but it can also remove any remaining contaminant oxides from the product, protecting it from further damage. Metals that form oxidation layers, among others, include aluminium, bronze, brass and copper, as well as precious metals such as gold and platinum. Similar to rust and oxides, the
removal of grease, mould, dirt and paint is often done prior to metal welding or bonding to ensure a strong, contaminant- free bond. Thankfully, laser cleaning is very capable of removing even the thickest layers of such unwanted coatings. With traditional cleaning methods, removing layers of chrome- or lead- based paints was previously a long, laborious and dangerous process. Lasers, however, can be used to safely remove such hazardous paints without creating additional waste.
Non-metals
As with metal cleaning, calibrated properly, lasers can be used efficiently to ablate unwanted materials from ceramic surfaces without damaging the underlying substrate. Ceramic products frequently cleaned using lasers include print rollers, ceramic moulds, historical artefacts and baking moulds. The flexibility of laser cleaning
also makes it suited to removing grime and bacteria from natural stones such as marble, granite, limestone and concrete. In
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