The combination of particulate and fumes can be harmful to operators, violate local safety codes, lead to combustion hazards, and jeopardise your considerable investment in equipment - things the laser sales people and the operating manuals usually don't mention. Laser cutting operations generate extremely fine particulate and dusts that can accumulate quickly and cause extensive damage-even optical distortion that misaligns the laser's focus.
Fumes from Metal Applications
Most metal operations using lasers generate primarily fume particles, and if oil is present, a secondary contaminant of smoke. Molten metals combine with oxygen and condense into a small, dry particulate typically 0.5 microns or smaller in size. For example, cutting or welding common steel produces iron oxide, a particulate similar to baby powder.
Plastics and Composites Applications
When cut with a laser, plastics and composites give off oily fumes and smoke from the plasticizers used in manufacturing the materials. While these fumes are relatively easy to collect, the accompanying gases and vapors are much more difficult to collect because of their small size. With the enormous number of different plastic compounds available in industry, it is impossible to select a gas/vapor media that is applicable to all plastics and composites used in manufacturing today.
Filter Requirements and Options
No single air extraction system or filter medium will collect all gases, vapors, smoke, dust, fumes, and particulate from all laser operations. Here is an overview of the main types of systems available:
Electrostatic precipitators are highly efficient for collecting the small submicron fume and smoke particles from many laser operations. Particles are first charged and then collected on oppositely charged collection plates. Filters are cleanable, eliminating repetitive replacement costs of disposable filters. If contaminants are oily or sticky-such as from certain composites and plastics or oil-coated metals-collection components can be washed. The main disadvantage to EPs is that they require routine service to maintain high collection efficiencies.
Cleanable Mechanical Filter Systems.
In both the two main types-fabric systems and rigid cartridge filters-air is drawn through mechanical filters, where suspended particles are removed from the airstream. Fabric filters are cleaned by shakers, vibrators or reverse air pulse, while cartridge filters are typically cleaned by a reverse pulse of compressed air. The main advantage of these systems is their ability to handle heavy concentrations of contaminants; the principle disadvantage is the high horsepower motors required to pull air through the filters.
Disposable Mechanical Filter Systems.
Generally these systems consist of one or more modular housings containing a variety of progressively higher efficiency disposable filters. In laser applications, a HEPA final filter stage is usually needed to capture the submicron particulates. These extremely flexible systems can collect both large and small contaminants efficiently, and are suitable for combustible contaminant applications. They're even adaptable to process changes by using alternate replacement filter media. The main disadvantage is higher costs for filter replacement in heavy or severe applications.
Because of the immense variety of contaminants generated by laser operations, specialized hybrid systems may be required. For example, a cartridge filter may be used for collecting particulates and a carbon module added for gas/vapor control. Or a fabric filter may be used for dry dusts and fumes, along with an electrostatic precipitator for oily contaminants.
If you have a laser system installed or are contemplating purchasing one, make sure the filtration system can handle all the various contaminants generated by your operations. A good filtration system will protect your investment in the equipment and safeguard the operators from the harmful contaminants.