Method to estimate attractive force in a permanent magnet chuck

A method of estimating magnetic attractive force obtainable in a design for a magnetic chuck where the design comprises at least one magnetically soft body and at least one permanent magnet body arranged to provide, during operation of the chuck, a closed path of magnetic flux extending through the at least one permanent magnet body, the at least one magnetically soft body, and a working surface of the magnet chuck, the magnetically soft body having a first surface to constitute at least a portion of the working face of the magnet chuck, the magnetically soft body having a second surface in face-to-face contact with a surface of the at least one permanent magnet body, the path of magnetic flux to pass from the at least one permanent magnet body through the magnetically soft body and through the first surface of the magnetically soft body;

• the method comprising:
• determining the design area of the first surface of the magnetically soft body;
• determining the total area of the designed surfaces of the at least one permanent magnet body in face to face contact with the magnetically soft body;
• obtaining an area-to-area ratio of (a) design area of the first surface of the magnetically soft body and (b) the total area of the designed surfaces of the at least one permanent magnet body;
• and
• comparing the obtained area-to-area ratio with like data of at least one area-to-area ratio obtained from at least one working magnet chuck of known magnetic attractive forces.