Laserbeschriftung von Hartferritmagneten zur Kennzeichnung von Druckgussteilen

With the presented method of magnetic labeling die cast components are labeled and provided with production data as well as protection against plagiarism. The magnetic labels are cast close under the surface of the component during the casting operation. Serial numbers, data and graphical information was engraved on the surface of hard ferrite magnets by laser marking using a diode-pumped ytterbium fiber laser. The data and graphical information was encoded as data matrix codes. Inexpensive strontium ferrite magnets were used. Melting processes and thermally induced material changes on the magnet surface during the laser labeling of the magnets results in a local demagnetization. The measurable decrease of the magnetic field strength is a result of local heating above the Curie temperature and the geometrical change of the magnet surface. The patterns with changing magnetic flux density can be visualized directly by a magnetic viewer or measured by magnetic field sensors such as Hall effect sensors. This paper deals foremost with the laser labeling process and the induced changes on the surface of the magnets as well as visualization and measuring test. First results of casting trials are presented, to confirm the stability of the magnetic labeling procedure during the casting operation.