German moulder Oechsler worked together with the LKT chair of plastics at Erlangen
Nuremberg university to develop a novel system for production of a three-component
rotary signal transmitter with an automatically-inserted Hall effect sensor.
Production of the part - which consists of a magnetic disc, carrier plate with shaft
and a protective cap - was demonstrated on a 70-tonne Arburg 370S injection moulding
machine at K2010.
One of the novel aspects of the process is injection moulding of a multi-polar
magnet, which is orientated and magnetised in the mould. This moulding is produced in
a ferrite filled polyamide 6 compound (LKT also produces a PA12 version ) supplied by
Mate of Japan. The compound contains a combination of strontium ferrite with a
remanence (Br) of 430 milli-tesla (mT) and neodym-iron-boron (Br = 1340mT).
An Arburg Multilift V vertical robot is employed to transfer the magnetised plastic
disc to the second station on the ejector side of the mould and to insert a sensor
component, which is encapsulated by overmoulding with an easy-flow BASF 30% glass
fibre reinforced PBT. This final overmoulding stage forms the carrier plate and the
integrated shaft for the rotating magnetised disc.
Meanwhile, the magnetic disc's MABS protective cap was moulded in a BASF resin at a
third station. The Multilift V robot then assembles the cap, carrier plate and disc
to form the complete rotary encoder.
LKT developed the proprietary ferrite filled PA compound for its polymer-bound magnet
(PBM) technology, selecting the fillers for optimum orientation in magnetic fields.
The institute also developed the concepts for moulding and in-cavity magnetisation of
axial, radial, diametric and multi-polar PBM magnets.
Simulation studies were made at the university to optimise the geometries and pole
structures of PBM magnets. This included magnetic field flow optimisation for multi-
polar magnetic rings used in special sensor and motor applications, as well as on
production tools and magnetising equipment.
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