Page 32 - MetalForming Magazine May 2023

Special Section: FABRICATION
LASER CUTTING DUST COLLECTION
30 MetalForming/May 2023 www.metalformingmagazine.com
Fabricators upgrading from older CO2 machines to high-speed fiber laser cutters, which produce dust at a higher rate due to higher cutting speeds, also may need to upgrade their dust-collection systems to handle the increased dust volume and dust-production rate.
suitable for collection of different dust types, ranging from submi- cron particulate to coarse, abrasive dust encountered in grinding and finishing processes.
The dust collector must be sized properly for the volume of dust produced and the amount of airflow required for collection. Two main factors affect sizing:
1. Airflow. The collec- tor must have enough airflow, measured as ft.3/min (CFM), to main- tain the required cap- ture velocities for the vol- ume of air that must be moved. Efficient hood design will minimize CFM requirements.
2. Air-to-cloth ratio. The collector must have sufficient filter media for the volume of air being moved and the amount of particulate generated. The heavier the particulate load, the more filter media needed per CFM—a lower air-to-cloth ratio. In general, laser cut- ting applications will require a lower air-to-cloth ratio than laser welding, with ratios typically between 1:1 and 0.5: 1, or 1 to 2 ft. of filter media for each CFM of air. An excessive air-to- cloth ratio will cause filters to load too quickly, requiring more-frequent replacement.
Filter Selection
Working with submicron particles created by thermal processes makes choosing the right filtration strategy very important. Such scenarios typi- cally call for a dry filter with a rating of MERV 15 or above. A MERV (mini- mum efficiency reporting value) rating identifies the overall effectiveness of dust-collector filters on a scale of 1 to 16 as to how well they trap small cir- culating particles. MERV 16 or HEPA filtration may be required to meet strict PELs for highly hazardous substances
capture the fume? In general, the closer to the source that fume can be cap- tured, the more efficient the system will be. Keeping robotic processes enclosed eases the ability to capture emissions and prevent fugitive fume from prop- agating throughout the facility.
Enclosure or Hood Design
The first step to designing an effi- cient fume-capture system for laser processes: Consider the hood or enclo- sure. We recommend source-capture systems, which collect fumes close to the source as they are emitted, for high- production laser processes. Many com- mercial laser cutting machines already are enclosed; these machines may or may not include their own integrated fume-collection system.
Robotic laser welders may contain fumes under a hood. Alternatively, a fume arm or intake plenum may be positioned to pull fume away from the weld seam. For manual laser welding, a fume arm or backdraft table should
be used to pull fumes away from the welder. The right solution depends on the size of the assembly being welded and the mobility of the welding arm, among other factors. Minimizing the amount of air that must be moved for efficient capture of fumes will reduce system energy consumption and oper- ating costs.
Dust-Collector Type and Sizing
Cartridge-style dust collectors prove ideal for collection of fumes from laser cutting or welding. Cartridge collectors come in many sizes, from small portable units that can support a single cutting machine or welding cell to large units ducted to multiple machines or cells throughout a facility. These col- lectors, highly versatile for machining and metalworking applications, offer higher energy efficiency and lower physical footprints than baghouse-style collectors of similar airflow. Cartridges are available in a range of media types and efficiency ratings, making them