Contaminated Optics within a Laser Cutter

Some of the most important components of a laser cutter are the optical elements. These are components that either deflect the beam (mirror) or allow the beam to pass through (lens).

Even when completely new, all optical components will cause some degree of attenuation: in other words, remove a small amount of laser power. Therefore, especially when the design of a laser cutter incorporates a large number of optical elements the laser power that arrives at the lens is less than the power that emits from the laser source.

Contamination of the optical elements of a laser cutting machine causes further attenuation and if left unchecked can have a massive detrimental effect on cutting speeds and in turn production efficiency.

Attenuation is more of an issue where the laser cutting machine incorporates a laser source of a lower power.

For example, if a laser cutter outputting 30w incorporates four mirrors, a combining optic for a positional diode and finally the lens, then if each element draws 2 watts of power the net attenuation is a 27% (almost 1/3rd) power loss.

Contaminated optics can often draw much more than 2w of laser power so it’s quite possible that a laser cutting machine <50w can be losing more than half its potential power simply through optical attenuation and/or contamination.

Laser optics will suffer accelerated contamination if the main application creates a high amount of debris; for example, laser cutting wood or laser cutting card. An ineffective or incorrectly specified exhaust system will further compound this problem

Low levels of contamination of laser optical elements can be easily cleaned, however, if the contamination is allowed to build-up too much it is often impossible to remove. At some point an over-contaminated optic will draw so much power that the heat generated will cause it to fail catastrophically.

For these reasons optical elements within a laser cutting machine are deemed consumable items so for users where the laser cutter is of strategic importance it’s a wise precaution for the user to hold stock of replacement optics.

Over-cleaning of optical elements can cause undesirable removal of the coatings, which is almost as bad as not cleaning them enough. As a general rule of thumb it is the frequency of checking for contamination that is more important and optics should only be cleaned if they show obvious signs of contamination.

With most system designs, optics that are closer to the focal point will contaminate faster than those that are closer to the laser source so, for example, inspection of the lens should be performed far more frequently than the first mirror.

We cover the cleaning of laser optics in another article.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions and we pride ourselves on the quality and depth of knowledge of our support staff. Our experts would be happy to advise you on this or any other aspect of your laser system maintenance.