Bonded magnets : Which materials?
OPM supports you in materials selection
OPM bonded magnets,
recognized expertise.
Thanks to its recognized expertise in the field of plastic-bonded magnets, OPM Plasto-aimants masters the entire design and manufacturing process, from material formulation to final product shaping. This expertise enables us to offer high-performance magnetic solutions tailored to a wide range of industrial applications. To learn more about our expertise and manufacturing processes, visit our dedicated page.
Discover the materials used to
manufacture our plastic-bonded magnets.
FEPLAST: ferrite bonded magnets
injected BHmax 3 to 16 kJ/m3 complex shapes
Description
A thermoplastic composite material consisting of a polyamide base combined with hard ferrite powder made from strontium or barium carbonate. Thanks to its excellent rheological properties, FEPLAST enables the production of complex shapes with the highest precision. Molding is performed by injection under pressure, making it possible to achieve overmolding and bi-injection of plastic with plastic-bonded magnets.
Injection is well suited to large and very large production runs. FEPLAST can be machined.
Benefits
The possibilities of complex shapes enable several functions to be fulfilled with a single part:
- Magnetic requirements,
- Drive (gears, etc.),
- Overmolded shafts,
- Various accessories
This technique eliminates the need for certain additional assembly operations, resulting in significant cost savings and reducing sources of defects. In addition, this process allows for narrow tolerances (0.1 to 0.03 mm).
Mechanical characteristics
Thanks to their plastic matrix, FEPLAST magnets offer better resistance to mechanical impacts than sintered hard ferrites and are notably less brittle. This material has good tensile strength, which means that its performance at high rotational speeds is excellent.
Chemical characteristics
FEPLAST is highly resistant to chemical attack and completely impervious to corrosion.
Magnetic properties
Due to their low density, the magnetic characteristics of these materials are not as high as those of sintered hard ferrites. Nevertheless, anisotropic FEPLAST offers B-Hrax values of 15 kJ/m3 and above. In addition, tight tolerances minimize air gaps.
- Isotropic FEPLAST: This material has no preferred orientation and can be magnetized in any direction (axial, radial, and multipolar).
Tooling costs are lower than for anisotropic FEPLAST, but the B-Hmax is also lower (3 cube kJ/m max).
- Anisotropic FEPLAST: This product has a higher specific energy because the particles are oriented during injection.
The orientation direction is chosen according to the type of magnetization required (radial, axial, or multipolar).
Tooling costs for this material are higher than for isotropic material due to the required tolerances.
Prototypes
The validation of a magnet sometimes requires a prototype phase. OPM can design and produce a prototype mold and supply prototype parts.
NEOPLAST: Neodymium bonded magnets
NdFeB – injected B-Hmax 32 to 48 kJ/m3 complex shapes
Description
A thermoplastic composite material consisting of a matrix, usually polyamide, combined with isotropic neodymium-iron-boron powder. Thanks to its excellent rheological properties, NEOPLAST enables the production of complex shapes with very fine geometries.
Molding is performed by pressure injection, a process that also allows for bi-injection of plastic with plastic-bonded magnets. This injection molding technology is particularly well-suited for large and very large production runs.
Benefits
Molding possibilities are the same as for FEPLAST and therefore offer the same advantages. Typical tolerances: 0.1 to 0.03 mm.
Mechanical characteristics
The composition includes a polymeric bonding agent that makes this material much less brittle than sintered neodymium and, in particular, less friable. The integrity of this material at high rotational speeds is excellent thanks to its high tensile strength.
Chemical characteristics
When used in a wet and aggressive environment, surface protection treatment (parylene, paint, resin, etc.) should be considered.
Magnetic properties
Given their isotropic nature, these materials can be magnetized in all directions (axial, radial, and multipolar). Their excellent coercivity allows for thin-walled shapes to be produced. Due to its lower density, it is not possible to achieve the flux values of BREMAG 10 with NEOPLAST, but the shaping possibilities are greater.
Prototypes
If validating the magnet requires a prototyping phase, OPM offers the same possibilities as for FEPLAST.
The dimensions of the standard shapes available are the same. If machining is required, two precautions must be taken beforehand:
- Generous spraying with water to limit heating; excessive heat irreparably affects the magnetic properties.
SAMPLAST: Samarium-Iron-Nitride Bonded Magnets (SmFeN)
SmFeN – BHmax up to 89 kJ/m³
Description
Plastic-bonded SmFeN magnets consist of SmFeN powder incorporated into a plastic matrix. Depending on the operating temperatures and ambient conditions, the matrix materials used are polypropylene (PP) or polyamide 12 (PA12).
Unlike isotropic plastic-bonded NdFeB magnets, anisotropic SmFeN powder is mainly used. This results in significantly higher remanence values, typically reaching 710 mT, with a maximum energy product (BHmax) of up to 89 kJ/m³.
Compared to NdFeB magnets, SmFeN magnets are subject to much lower fluctuations in raw material prices, which means that price stability can be expected throughout the duration of a project.
Prototypes
If magnet validation requires a prototyping phase, OPM offers the same possibilities as for FEPLAST.
The dimensions of the standard shapes available are the same. In the case of machining, two precautions must be taken beforehand:
- Spray abundantly with water to limit heating; excessive heat irreparably affects the magnetic properties.
- Protect machined surfaces from corrosion, for example with paint or acrylic lacquer.
Material
Composite material.
Distinctive features
Plastic-bonded SmFeN injection-molded magnets are more elastic than pressed magnets. However, due to their high filler content, they do not achieve the mechanical properties of engineering plastics. For example, gears can be molded directly from the magnetic material, but these can only be subjected to low stresses, as their sliding properties are inferior to those of unfilled plastics.
Magnetic properties
The magnetic properties of injection-molded plastic-bonded magnets vary depending on the filling ratio and the type of magnetic powder used. The maximum operating temperatures range from +120 °C to +140 °C, depending on the magnetic material and the plastic matrix. In the case of unfavorable shapes — particularly thin walls or narrow pole pitches — variations in properties may occur due to excessively rapid solidification or an insufficient orientation field.
Corrosion resistance
As with all composite materials, the chemical resistance of injection-molded SmFeN magnets depends both on the plastic matrix and on the magnetic material. Magnets with a polypropylene (PP) matrix offer much better water resistance than those bonded with PA. However, use in water must be validated on a case-by-case basis.
FLEXOR: Calendered elastomer
B-Hmax 8 to 11 Kj/m3 simple shapes
Description
FLEXOR is a calendered, cold-hardened, semi-anisotropic plastomagnet based on synthetic elastomer and ferrite powder.
Benefits
FLEXOR is a flexible material. Produced in sheets or rolls, FLEXOR can be easily cut using a punch, which means that tooling costs are low.
This material is particularly well suited to small production runs, but can also be used for medium and large production runs.
Mechanical characteristics
Flexor’s flexibility means it’s not brittle. However, its yield strength is low due to its high magnetic powder content. Its hardness can be changed.
- Tolerances± 0.25 or 1% beyond 250 mm.
- Thickness: -0; + 0.25 mm (very abrasive material for punches).
Chemical characteristics
When using oil, its compatibility with the elastomer must be verified. The composition of FLEXOR can be modified if necessary.
FLEXOR is not susceptible to corrosion.
Magnetic properties
This material has low specific energy (8 to 11 kJ/m3). The calendering process gives it its anisotropic properties. In some cases, the magnetic properties of FLEXOR can be improved by adding a sheet metal layer on the secondary magnetic face.
Possible shapes
Only simple shapes are possible since punching is used to obtain them.
Prototypes
Certain standard shapes are available in FLEXOR 15 for cutting prototypes.
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