Injection molding

Sprox® magnets are manufactured from isotropic or anisotropic magnet materials. Barium ferrite or strontium ferrite powder is compounded with thermoplastic binders to form a granulate suitable for injection molding. The granulate is then processed in customized injection molding machines using specially developed tools. This inexpensive material can be magnetized in a variety of patterns by applying magnetic fields in the injection molding machine. Subsequent magnetization is often not required. This technique is particularly cost-effective for long production runs.

The Neofer® p magnets use an isotropic NdFeB-based rare-earth material which is compounded with thermoplastic binders. The Neofer® p material types are magnetized after molding, since they are isotropic and thus not directional.

The advantage of the injection molding process for producing magnets lies in the wide range of shapes that can be produced. It is also possible for inserts such as axles, bushes or rings to be molded in, with the inserts being loaded by hand or fully automatically, depending on the quantity produced. The costs of assembly operations can be reduced as such materials allow press-fit, snap-fit and positive-fit connections with motor shafts etc.

The production process allows products to be manufactured within such tight tolerances that no reworking is generally necessary. Depending on the size of the molding, the tolerances that can be achieved are in the range 0.03 through 0.25 mm. As required, polymer-bonded materials can be turned, drilled, milled and ground and they are not as brittle as sintered materials.

The proportion of synthetic plastic materials of typically ten percent by weight mean that the magnetic properties lie below those of unmixed material. On the other hand, with anisotropic grades, it is possible to achieve a directional magnetization during the injection molding process. This in turn improves the magnetic properties.