OIL MIST FILTRATION IN CNC MACHINING CENTERS

CNC machining centers, which are used in almost all sectors today, especially in the automotive, medical, defense and aviation industries, use coolant and lubricating fluids while processing metal.

CNC oil mist filtration

The high temperatures generated during processing cause these liquids to evaporate rapidly. Inhaling these vapors poses a health risk, and their release into the atmosphere is prohibited. These oil droplets remain suspended in the air and can range in size from 1 to 10 microns, while oil mists can range from 0.1 to 1 micron. The current OSHA standard for mineral oil vapor is 5 mg of mineral oil vapor per cubic meter of air averaged over an 8-hour work shift and 15 mg/m3 of TWA (total particulates).

These vapors can also cause significant damage to sensitive mechanical and electronic systems in machinery. When their concentration increases and they reach the lower explosion limit, they pose a risk of explosion due to contact with surfaces heated above 200 degrees Celsius and a spark.

The formation of oil mist and oil fumes isn't limited to CNC machining centers. They also occur in oil grinding, forging, some plastics processing, heat treatment, casting, and other machining processes. See our case study on the cold forming process.

For all these and similar reasons, oil vapor absorption and filtration systems must be used to filter these vapors as quickly as possible and to recover and reuse these condensed liquids.

These systems can be specific to each machining center, or they can be designed centrally and absorb and filter oil vapors generated in multiple CNC machining centers simultaneously.

Esta Oilmac oil mist extractor

These filtration devices can utilize centrifugal, electrostatic, or mechanical filtration. Each manufacturer utilizes a different technology to separate oil vapors.

How can we calculate which flow rate oil mist filter to use in a machining center?

The volume of the enclosed area of the machining center is calculated in m³ by measuring the width x length x height. The equipment inside the cabinet is then subtracted from this volume (usually 20% of the volume). While this calculated net volume can vary depending on the steam density, the required flow rate can generally be easily calculated by multiplying it by 360 ACH.

CNC machine dimensions

For example, if the enclosed volume of a machining center is 2 m³, subtract 20% of the equipment volume to obtain a net volume of 1.6 m³. Multiplying this volume by 360 gives an oil mist filter with a flow rate of approximately 576 m³/h.

Many CNC machining center manufacturers drill at least one suction hole in this enclosed volume for the pipe/hose connection. This hole allows for connection to the filter system. Additionally, many manufacturers specify the required air flow rate in their user manuals.