Composite materials are used for the production of plastic-bonded, pressed magnets. They consist of magnetic powder that is embedded in a plastic matrix. Derived from the forming process, a distinction is generally made between two main groups of plastic-bonded magnets: injection-moulded and pressed.
For pressed, plastic-bonded magnets, NdFeB powder is embedded in a thermosetting plastic matrix. Epoxy resin is one of the materials used as plastic. Plastic-bonded NdFeB magnets are axially pressed into moulds. As a result of the very high filling degree of up to 97% NdFeB powder (percent by weight), much higher magnetic values can be achieved compared to plastic-bonded, injection-moulded magnets. Compared to the tools required for injection-moulded magnets, the tools for pressed magnets are less complex and less expensive.
Compared to sintered magnets, much more delicate shapes can be produced with plastic-bonded, pressed magnets. For example, thin-walled rings with Ø 27 x Ø 24 x 30 mm and diameter tolerances of only ±0.05 mm can be produced. Generally, no additional mechanical machining is required. However, if the requirements are particularly high, the magnets can also be ground to more narrow tolerances.
A typical data sheet for a permanent magnetic material contains its key magnetic and mechanical characteristics. The magnetic characteristics are usually measured in accordance with DIN EN 60404-5.
In addition to magnetic values, the data sheet also contains mechanical characteristics such as density, hardness and strength properties.
The magnetic characteristics of plastic-bonded, pressed magnets vary depending on the magnetic powder being used. The possible maximum operation temperatures vary between +130°C and +160°C.
In case of unfavourable shapes, in particular those with thin wall thicknesses or narrow pole pitches, there can be deviations in the material data.
The chemical resistance of plastic-bonded, pressed magnets is determined by the plastic matrix as well as the magnetic filling material. Pressed magnets feature a plastic content of approx. 10-20 vol.-%, and, compared to injection-moulded magnets, they cannot be produced as dense bodies. While the resin coats the magnetic particles, in corrosive conditions they are offering a greater area of vulnerability than injection-moulded magnets.
In the vast majority of cases, plastic-bonded, pressed magnets are used unprotected. For critical applications, the chemical property or the corrosion resistance can be further improved by adding a plastic coating.
In the past, MAGNETIC ROTORS were manufactured in multiple successive PRODUCTION PROCESSES, which was very costly. Magnetic rings were built and, in a second production step, glued to the shaft. In addition, depending on customer specifications, a burst protection in the form of a stainless steel sleeve was shrunk and glued onto the magnets. Thanks to our new production technology, it is now possible to combine all of these processes into a single step.
- no adhesive bond
- no additional step
- inexpensive production
- high engine speeds possible
- Goods receipt purchased parts (shafts, bushes, soindles, etc.), epoxy resins/additives, magnet powder
- Inspection of incoming raw material/components
- Pressing and assembling in bushings/pots possibly pressing in shafts/bushes
- Pressing without magnetic field (anisotropic)
- Pressing with magnetic field (isotropic)
- Magnetising, marking, coating according to customer specifications
- Outgoing goods inspection
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Automated manufacturing processes, e.g.: Feeding of components, Magnetisation, magentic and/or visual/mechanical inspection, packaging
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