Spreading magnets
When piles of sheets of different thickness are unloaded, double sheets could occur despite the use of spreading magnets, and this all the more, the thinner the sheets. The effects of a spreading magnet -either according to the electromagnetic or the permanent magnetic principle- are based on a magnetic flux admitted to the sheet so that magnetic poles of the same kind are generated in the sheet which then repel in the same way as two magnetic north or south poles would do. This repulsion effect isolates two sheets lying directly upon each other. This is especially required if the blanks were oiled before and have been under pressure for some time with the sheets showing a strong sticky effect. This cannot be avoided in the usual processes, because the sheets must be protected against corrosion until the following process stage begins. As a general principle two different kinds of spreading magnets are differentiated: The purely permanent magnetic spreading magnetic system and the purely electromagnetic one.
Types
» Permanent magnetic spreading magnets
» Electromagnetic spreading magnets
Technical explanations
» Saturation
» Trouble effects
» Edge covering
» Operating time
» Coil Design
» Different possibilities of positioning the spreading magnets
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