subject: Permanent Magnetic Chucks: No Power Required [print this page] Permanent Magnetic Chucks: No Power Required
Permanent magnetic chucks offer all the time-saving advantages of any magnetic workholder with one additional benefit: they do not require electrical power to maintain a magnetic holding force.
A magnetic chuck is a specialized clamp used to hold work pieces. It is typically used in place of mechanical clamps and vises because it saves set up time and provides the strong and uniform holding force required for grinding, turning or other machining operations.
Permanent Magnetic Chuck Construction
A permanent magnetic chuck uses high-powered ceramic magnets to generate a magnetic holding force. They consist of two matching packs of magnetic materials. The magnetic force is actuated with a mechanical lever. The lever aligns the packs to direct the magnetic force from the top plate through the work-piece and finally to the bottom plate, completing the magnetic circuit. When the lever is reversed, the magnetic forces are contained within the chuck's plates and away from the work piece, which allows the piece to be released.
Magnetic Circuit Designs
Magnetic chucks develop their magnetic "clamping" force from one of three designs: permanent magnets, electro-magnets or electro-permanent magnets. Both electro-magnets and electro-permanent magnets require electrical power but in different ways. Electro-magnets use an external controller that produces a DC voltage in a coil surrounding mild-steel pole pieces of the chuck. The poles remain magnetic as long as the DC voltage is applied. Electro-permanent magnets use the same type of DC voltage to energize the magnet but it will maintain its magnetic field and holding force even when power is removed. In order to de-energize the electro-permanent magnet, power must be applied.
No Power Required
Permanent magnets offer an advantage over electro-magnets or electro-permanent magnets: they do not require electrical power. Manufactured with powerful neodymium magnets which claim a 30 percent higher holding force than micro pitch magnetic chucks, permanent magnetic chucks do not need electrical power to operate; therefore, they are immune to power failures.
If power failures (blackouts), power degradations (brownouts) or power anomalies (sags, spikes, and surges) are a safety and operational concern, permanent magnetic chucks offer an additional level of security to protect workers.
