Mist Collection for Air Quality

The appearance of a CNC machine shop today is vastly different from the noisy, dirty manual shops of just a few decades ago. Advances in technology have produced CNC machines that can look like small buildings organized along the shop floor. No matter what advances in cutting is made, however, the cutting of metal produces waste that can be damaging to machines, tools, and people. One of these sources of waste was introduced with coolant used for high-speed machining. The coolant, though effective in capturing chaff and reducing friction releases contaminants into the air with the mist it expels. The basics of physics tell us that exposing a liquid to heat will produce vapour. When that vapour also grabs tiny pieces of oil and metal, mist collection for air quality is necessary.

What Is Mist?

The introduction of coolant systems introduces water or oil, and chaff together as a by-product of cooling the cutting tools during high-speed CNC machining. This extends tool life through reduced friction that presents warp and wears on the tool. Compressed air may also be used to aid in precision production and produces its own mist through humidity present in the shop. Mist, itself, doesn’t seem dangerous but the blend of tiny particles of metal, chemicals, and oil produces several safety considerations.

Safety

Several factors present themselves for employee safety. Exposure to these fine particulates can cause skin and eye irritation. Respiratory complications can arise as particulates accumulate in the airways also. Oil smoke may also be produced when the mist is exposed to high temperatures during processing which further exacerbates breathing problems. National safety boards limit the exposure to inhalation of oil mist making the collection a legal requirement. The shop floor, tools, and equipment can also become slick with oil mist as it settles creating further safety hazards.

Safety also extends to equipment as both oil mist and oil smoke will compromise CNC machine parts. Debris settling on the cutting tools can affect friction and heat buildup affecting accuracy and reducing tool life as well. General humidity and, more so with oil mist, can also cause arcing and shorts in electronic components. The balance of airflow and humidity in the air must fall in a safe range to avoid static electricity on the opposite end of the moisture scale which also adversely affects electronic performance.

Maintenance

Systematic maintenance is a vital part of CNC machining operations to extend tool life, create precision parts, and prevent costly breakdowns. Mist collection for air quality assists in keeping all equipment free from oily debris collection. The obvious tools and machines are easy to identify for maintenance. They are cleaned between jobs in any quality machine shop. Longer production runs will build up a considerable amount of chaff and oil mist that need attention during production. Consider, also, the auxiliary equipment that collects this oily sludge, such as overhead fans, circuit boards and monitors, raw material stock, filters, and even walls and doors. Electronic equipment in particular will overheat if the mist builds up to block airflow resulting in costly repair or replacement. More and more electronics are seen in a CNC machine shop as sensors and other AI solutions are added to production.

Mist can also find its way back into coolant systems adding bacteria that will corrode metal and compromise seals on coolant pumps. Larger filtration systems, like HVAC equipment, will overheat and run less efficiently, eventually needing repair and replacement also with oil mist buildup. Regular shutdown for larger maintenance projects can be reduced by simply capturing mist at its source.

Approaches

In most manufacturing facilities you will find large fans and air filtration systems to meet Occupational Health and Safety guidelines. Capturing oil mist through standard filtration requires a high level of maintenance to replace filters on a strict schedule to prevent loss of airflow. De-humidifiers can also help keep air dry, especially used in conjunction with compressed air systems.

Some CNC machining facilities may need to meet even higher air purity standards, similar to food production or medical environments, if they are producing sensitive equipment. Working with HVAC, air purification filters, and mist collection can provide a hygienic environment.

The best place to collect mist is at the source. Mist collection equipment is much more effective at the machine tool than allowing it to collect inside a CNC machine enclosure, although this also helps prevent release into the surrounding work area. Source collection eliminates all the extraneous air and surface contamination reducing safety risk and maintenance.

Further Benefits

One of the most effective methods for mist collection is with equipment connected to the CNC machine that collects mist before it is released into the air. By use of centrifugal force, the mist is collected into larger droplets which can be gathered and recycled similar to coolants for re-use. This further protects the environment from the disposal of dirty coolant and saves the machine shop money by re-using coolant several times.

Additional operations in a CNC machining facility may include laser engraving, welding, and 3D printing. Installation of mist collection equipment works just as effectively for the mist, smoke, aerosols, fumes, odours, and exhaust produced from these operations as well. As machine shops continue to grow through added manufacturing services and the addition of more high-speed processes, mist collection for air quality will continue to evolve to serve maintenance and safety needs.