Machining Fluid Filtration and Particle Count Measurement

Machining fluid recovery from a chip wringer – fluid being pumped from chip wringer sump through a “screen” to a fluid recovery tote

Metalworking cutting fluids used to cut metal in large industrial machine shops such as automotive engine and transmission plants, are often used in closed systems where the fluid is filtered and returned to the machine tool.  Large systems may pump slurries of machining chips and cutting fluid to large central filters.  Additional filtration is performed within the machining fluid system and varies in style, but self-cleaning candle filters are common.  Bag type filters are also used.  Systems machining magnetic materials can utilize magnets to attract particulate, but systems machining non-ferrous materials have to rely on filters to remove particulate.  Chip wringers (centrifuges) are used to remove machining fluids from the metal chips produced during machining operations.

Some machine shops send the fluid removed from metal chips in chip wringers to process waste and some recover the fluid so that it can be reintroduced to large machining fluid systems at the location of a large central vacuum or other filtration system.  Recovered fluid is either minimally filtered or not filtered at all prior to reintroduction to active machining fluid systems.  Machine shops that believe this fluid is detrimental to their active machining systems let it go to process waste. Buildup of particulate smaller than 5 microns (micron = 10-6 meter) in cutting fluid is viewed as problematic for filter systems and machine tools.  Modern machining equipment and practices tend to produce finer metal particles than historical practices.  This particulate can cause problems with fluid flow rates through filters requiring downtime for manual cleaning or changing of filter elements, blind filters and strip out desirable fluid components such as anti-foaming agents, decrease pump life, clog fluid flow paths in tools, etc.

Machining fluid is very expensive and needs to be maintained so it performs as intended for a long period of time without disrupting manufacturing throughput.  The cost to dump, clean, and recharge a system with new machining fluid is very high.