How to choose a dust collector for laser and plasma cutting platforms
Plasma and laser cutting, produce large amounts of fumes and particles that can pose health risks to operators and damage to cutting machine tools.
Often, dust collectors are required in cutting systems to reduce worker exposure to fumes and to help protect expensive cutting machine components. When designing a dust collection system, the challenges posed to the dust collector by various factors in the thermal cutting process need to be fully considered, including: fume particle size distribution, fume concentration, system pressure loss and combustible dust risk.
Cutting equipment manufacturers typically offer either dry or wet cutting tables that support the sheet being cut. For dry cutting tables, a cartridge dust collector is typically used, with the fumes being conveyed to the dust collector through ducts in the lower suction table.
As with any other process, the customer should perform a hazard analysis before selecting a de-dusting solution. Sparks are typically present in any thermal cutting process and much of the collected dust is combustible, posing a risk of explosion and fire. An ignition source solution should be considered for any dry dust collection system. In addition, the risks associated with mixing different metals should be considered.
In recent years, the Occupational Safety and Health Administration (OSHA) has significantly lowered the permissible exposure limits (PELs) for many dusts such as hexavalent chromium. This is particularly true for applications where chromium-containing metals such as stainless steel are cut, where chromium is significantly higher than other common metals such as carbon steel or aluminum. In indoor emission conditions, this problem can be even more pronounced.
Dust collector sizing for dry cutting tables first requires a determination of the airflow required to control fume spillage. In general, the wider the cutting table, the greater the airflow required to capture the fume and therefore the larger the dust collector required. Other factors also affect the airflow, including the size of the extraction unit, the percentage of sheet coverage, and the number of extraction units open at the same time during the cutting process. Down-suction tables are often divided into multiple suction units (or zones) to reduce the total airflow required to effectively capture the fume, thereby reducing the size of the dust collector. Dust collector selection is then customized based on the number of cutting heads, cutting technology (laser, plasma, oxygen fuel, etc.), the material being cut, and factors such as cutting speed and torch time zone division. For larger workpieces, multiple cutting machines can be integrated in a single down-suction table.
The airflow through the cutting table must be sufficient to create a descending airflow over the table surface to overcome the rising velocity of the fumes. The downdraft air velocity is the minimum air velocity required to prevent fumes and particles from escaping the cutting table and is typically 150-250 ft/min for thermal cutting applications, subject to adjustment based on cutting table design and size.
