Magnetic filters keep coolant clean

Manufacturing Engineering, Apr 2000 by Mackowski, John

Coolant cleaners are commonly used with surface grinders, gear grinders, honing and lapping machines, broaches, milling and drilling machines, face grinders, and oil-reclaiming machines.

Rare-earth coolant cleaners. They work the same way as the ceramic coolant cleaner, but use a rare-earth magnet, which maximizes magnetic field strength. The resulting high field provides effective separation response in any drum-type magnetic separator removing particles down to 3pin. (0.08 (mu)m).

Coolant cleaners are currently available that have a power source consisting of high-quality rare earth permanent magnetic material that develops magnetic fields many times stronger than conventional ceramic or Alnico magnets. With these systems, there is no increase in size, and the additional strength improves removal of very fine iron particles from a wide range of coolants and other liquids.

In operation, liquid contaminated with fine ferrous particles enters the sump area and flows past a counter-rotating magnetic drum. Particles attracted to the drum are held tight and lifted to the top, where a discharge device moves them to a chute. Clean liquid leaves the bottom of the separator.

Fine magnetic particles suspended in the dirty liquid tend to flocculate when introduced to the strong magnetic field. Because the floc also filters particles from the liquid, this further increases separation efficiency. Accordingly, this coolant cleaner is effective even on moderately magnetic particles.

Magnetic-cyclone filtration. When machining both ferrous and nonferrous materials on the same grinding machine, an additional level of filtration is necessary to capture the nonmagnetic particles. Especially effective at handling the high stock removal rates of throughfeed, centerless, surface, and small double-disc type grinders, magnetic-cyclone filters also remove steel wool from the coolant used by ID, abrasive belt, and free-abrasive grinders. As an example of this type of filtration, with water-based coolant, the Eriez unit removes particles down to Spin. (0.13(mu)m).

When dirty coolant from the machine tool enters a reservoir and flows through a magnetic coolant cleaner, ferrous particles, which are the bulk of the contaminants, collect on the magnetic roll and are discharged into a swarf bucket. The coolant and nonferrous contaminants fall into a tank below. Then, the filter pumps the almost-clean coolant to a manifold, which evenly distributes it to a second-stage filter, the hydrocyclone. A nozzle discharges the filtered particles, along with a small amount of coolant, into a portable swarf tank. Clean coolant leaves the hydrocyclone, is sprayed into the clean coolant tank, and finally returns to the machine tool.