Injection Moulded Plastic Magnet Assembly

By Paul Fears | 22 November 2018

Bunting’s engineering design team was asked by a customer to reduce the cost of a magnet assembly.  The magnet assembly formed part of a magnetic coupling with a specific torque ratio.  However, due to the manufacturing process, the cost of assembly was high.  Subsequently, the team looked at an injection moulded plastic magnet assembly.

The finished Magnetic Assembly
The finished Magnetic Assembly

Injection Moulded Plastic Magnet Assembly Development Project

The major challenge was that the magnet assembly was going to be coated in plastic using an injection moulding process.  The existing process involved the over-moulding of a Neodymium magnetised assembly.  This was proving the be difficult and costly.  Handling strong magnetised materials was difficult in the moulding process.

Additionally, the magnetised assembly was being exposed to excessive heat.  This would reduce the magnetic performance.

The Bunting engineering design team developed a magnetic assembly that could be magnetised after the injection moulding process. Two unique radially orientated sintered neodymium ring magnets were bonded together to make a long enough magnet to produce the required torque and would then create a 6-pole radial magnetic field when magnetised.

The ‘plastic’ component was then magnetised producing the strongest magnetic field possible for a magnet of this shape and size in an outer 6 pole configuration.

This has been achieved without any compromise in the operational characteristics and torque ratio as the Neodymium grade was increased to compensate for the increased air gap and the loss of the coupling back iron.

The Radial Magnetic Field
The Radial Magnetic Field

New Design Benefits

With the injection moulded plastic magnet assembly, the manufacturing cost has been reduced by 90%.  This has been achieved without any compromise in the operational characteristics and torque ratio.

Tooling costs, which were over £10,000, have also been significantly reduced.

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Magnet and Magnet Assembly Design

Bunting designs, manufactures and supplies a wide range of magnets, magnet setters, magnetisers, and magnetic assemblies.  Many are bespoke for specific applications.  For further information on any of the products mentioned in this article, or for bespoke magnet assemblies and magnet designs, please contact us via:

Phone:  +44 (0) 1442 875081


Via the Bunting-Berkhamsted website for specialist magnets, magnetic assemblies and magnetising equipment

Via Bunting-eMagnets for online purchase of Magnets and Magnetic Technology

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