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Plastomagnets

Plastomagnets

Introduction

Permanent magnets are manufactured either by traditional metal casting or sintering – the "ceramic" technology. However, both methods have their limitations in particular with regard to shape, complexity of the product and the achieved precision of dimensions.
The pressure on increasing productivity and the growing demands on precision led to the development of a special technology of permanent magnets, similar to the manufacture of plastics. A magnetic material in powder form is mixed with a powder binder on a base of resins and then pressed and hardened by heat, alternatively injected at heat in a semi-liquid state.
This enables the manufacturing of complicated magnet shapes with a precision of up to 0.01 mm (!), and it is even possible to manufacture, within a single production operation, a magnet-rotor together with a plastic pinion, a magnet with a pressed-in shaft, etc. During mass production productivity increases many times.

Properties

Plastomagnets are always made to order, so that the final shape precisely corresponds with the customer’s requirements. When designing a magnet, it should be taken into consideration that the magnetic properties are slightly lower than in an equivalent traditional magnet from the same material, as the volume share of the magnetic powder reaches "only" 60 to 80%.
Simpler parts are made by pressing, when higher magnetic parameters are achieved. Complicated shapes are made by injecting at increased temperatures, which is also less expensive.

Applications

Plastomagnets are used especially in industrial mass production. The greatest economic benefit is gained with series exceeding 10 000 units.

Magnetické vlastnosti - Plastomagnety lisované

Class Coercivity Remanence Max. product Working temperature
HcB [kA/m] Br [mT] (BH)max [kJ/m3] oC
BNP-6 304-360 520-600 40-56 140
BNP-8 360-440 600-650 56-72 140
BNP-10 360-464 650-700 72-80 120
BNP-12 424-480 700-760 80-96 130
BNP-8H 400-480 550-620 48-72 120


Magnetic properties – Injected plastomagnets

Class Coercivity Remanence Max. product Working temperature
HcB [kA/m] Br [mT] (BH)max [kJ/m3] oC
BNI-2 120-240 200-400 6,4-24 130
BNI-4 240-310 400-490 28-36 130
BNI-6 310-380 490-570 42-56 110
BNI-8 380-430 570-630 59-67 120
BNI-6H 330-400 480-560 40-52 110

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