Injection moulded polymer magnets from Sura Magnets AB of Sweden, instead of conventional metal magnets. This is the material that turned out to be the optimal solution in the manufacture of Alfa Laval Agri's revolutionary design for a new type of electronically-controlled pulsator to control the pulsed vacuum in milking machines. The final design is also an interesting example of an unusual manufacturing approach taken by a particular group of companies called PB Option. From an idea to a completed unit produced by multi-component moulding in one single process.

The mechanism in Alfa Laval Agri's pulsator for milking machines is based on a completely new type of valve solution, invented by Master of engineering Hans Olofsson. The valves in the pulsator create the required vacuum for milking around the outer wall of the suction cup by introducing a series of plastic strips back and forth over the air chambers within the pulsator. In order to generate the reciprocating movement on the valve axle, some form of magnet was required at the end of the axle.
If the component market's conventional metal magnets intended for industrial use were used, the new type of valve would require some precision work during assembly.

This would be necessary in order to fit the metal magnet into a cut-out on the axle of the vacuum-generating ribbon holder in the pulsator. This solution was not very satisfactory, considering the degree of demanding extra work involved in using this type of material.
Hans Olofsson and his colleagues thus searched for an alternative, more suitable material when determining the production process. They found that injection moulded magnet material from Sura Magnets would be ideal.
This has the required characteristics without the need for adding precision assembly to the manufacturing process. By means of a double injection of the "normal" material used for the valve axle, complemented by the magnetised plastic at the end of the trunnion, a complete finished product can be made in a single production process.
No finishing work is needed, such as the grinding that would be required for metal magnets to fit into the trunnion aperture, and fingertip precision assembly is eliminated.
Sura Magnets' injection moulded magnet material is said to meet both the quality requirements set by the valve tolerances and the economic needs for cost-effective competitive production of the new pulsator for milking machinery.
The injection moulding of the magnetic plastic material does however impose special demands on the moulding sequence. The magnetic material in the liquid plastic must be given a particular orientation in order to create the north and south magnetic poles. Nevertheless, this is a technique that Sura Magnets has mastered, and is expected to offer many interesting possibilities in future modern and cost-efficient designs.

Caption 1
Master of Engineering Hans Olofsson, a designer at Alfa Laval Agri, selected a unique patented pulsator design for the company's latest milking machines. The solution involves multi-component moulding of a magnetised plastic material that offers a number of advantages in manufacture and use.

Caption 2
This valve has been manufactured using multi-material technology. It is used in Alfa Laval's milking system.

For further information please contact
Dr. Martti Paju, Managing Director
Sura Magnets AB
Ringvägen 40
SE-614 33 Söderköping, Sweden
Telephone: +46-121-157 00, Telefax: +46-121-157 40
E-mail: martti.paju@suramagnets.se