Slip Ring

Slip Ring

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Circular or rotary magnetic chucks are designed to hold a rotating work piece. Grinding and turning operations are the typical applications for circular magnetic chucks.

A magnetic chuck is a 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 a strong and uniform holding force. They are manufactured in two footprints: rectangular and circular. Circular or rotary chucks are designed to hold a rotating work piece. Grinding and turning operations are the typical applications for circular magnetic chucks. These chucks are primarily used for holding parts such as rings or discs.

Construction

Circular magnetic chucks are constructed with brass and steel top plates with a concentric ring that gives maximum resistance to coolant and accuracy in work piece centering. Dowel pins or screws may be inserted in the top plate to withstand the high torque used on lathes, grinders and other machinery with heavy cuts. Chuck top plates may be machined for work with odd configurations. The top plate is magnetic with each pole individually magnetized by ceramic permanent magnets, so electrical controls and slip rings are not required.

Magnetic Pole Types and Pitch

Circular magnetic chucks can be constructed with transverse and longitudinal pole types. In transverse pole types, the poles run across the chuck from side to side. The pole spacing varies from chuck to chuck and determines how much of the workpiece can be magnetized. In longitudinal pole type, the poles run the length of the chuck. For thin work pieces narrow pole pitch is best while a wider pole pitch is better for thicker parts.

Types of Magnetic Circuits

Since these circular chucks are rotating when in operation, permanent magnetic or electro-permanent magnetic circuits are universally applied because they require no electrical power when in operation, no electrical controls or slip rings to transfer D.C. power from the control to the magnets.

Permanent magnetic chucks use high-powered ceramic magnets to generate a magnetic holding force. The magnetic force is actuated with a mechanical lever. The lever aligns the magnetic 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 and away from the work piece, which allows the piece to be released.

Electro-permanent magnetic chucks (commonly called electroperms) are constructed with a coil wound around permanent magnetic material embedded in the chuck plate. They use a chuck controller to apply a DC voltage to the coils to charge the magnetic material. This takes about 1 second and securely binds the work piece to the chuck. Electroperms will remain magnetic even when power is removed, which gives them a fail-safe feature.

DocMagnet Inc. designs and supplies Magnetic Workholding systems. Their Circular Magnetic Chucks make it easier to accurately and securely workhold rings.

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