Controlling the Quality of Permanent Magnets

The manufacturing process involved in permanent magnets means that inhomogeneities may occur in the distribution of the magnet material and therefore inhomogeneous magnetic fields at the surface. These defects are very difficult, if not impossible, to identify using standard magnetic field measurement instruments such as Hall probes or integral measuring methods. To achieve high lateral resolutions, the samples would have to be extensively scanned. Our magneto-optical testing systems provide a high-resolution image of the scatter field on the surface of the magnets in a matter of seconds. This means that even the smallest irregularities can be found quickly and documented reliably. For example, small inclusions can cause functional magnets to fail or indicate structural problems that can lead to cracking under mechanical stress.  

For quality control applications relating to stray field properties, a magneto-optical sensor system such as the cmos-magview offers a tremendous advantage over conventional methods. Areas of up to 45 x 60 mm² can be visualized more quickly with one image and then analyzed using software. This allows defects in the magnetic field or material to be identified and logged at a glance.

Besides measuring individual magnets, multi-pole permanent magnets can also be tested and measured. The demand for 100% end-of-the-line control is growing, especially in the area of functional magnets. Magneto-optical inspection allows for connection to the automation on existing process lines and can therefore be implemented with minimum time and effort.