Fig. 1 Engel’s special Liquidmetal all-electric E-Motion injection moulding machine

Injection moulding machine producer Engel Holding GmbH, Schertberg, Austria, has signed an agreement with Liquidmetal Technologies Inc., Rancho Santa Margarita, California, USA, whereby Engel will be the exclusive machine manufacturing partner for Liquidmetals’ unique patented process for producing components from amorphous alloys by Liquidmetal injection moulding.

The exclusive agreement was announced at the 2015 Engel Symposium held in St Valentin, Austria, June 16-18, where a special all-electric E-Motion injection moulding production cell (Fig. 1) was demonstrated for Liquidmetal injection moulded medical forceps (Fig. 2) from an amorphous alloy based on zirconium.

The amorphous alloys are available in the form of slugs cut from round rods. These slugs are automatically fed into a melting chamber where the material is induction melted under high vacuum. Instead of a screw normally used in injection moulding, the special Engel machine has a piston with which the molten metal alloy is injected into a thermo-regulated mould. Very rapid cooling leads to the formation of the amorphous structure in the zirconium alloy which gives the material its unique characteristics. Robots are used to remove the finished parts. The sprue can, for example, be removed with the help of a water-jet cutting machine or mechanical shears.

Fig. 2 Parts for medical forceps were produced from a Liquidmetal alloy at the 2015 Engel Symposium held in St Valentin, Austria

Dr Gerhard Dimmler, Engel Vice-President Research & Development Products, stated these amorphous materials are extremely hard, but at the same time highly elastic, with an elasticity of 2%, compared to 0.2% for steel and 1% for titanium. Liquidmetal amorphous zirconium alloys also have a low specific weight and excellent corrosion resistance, which make these alloys particularly suitable for moulding precision components. Additionally, the shrinkage rate during rapid solidification is extremely low (0.4%) which allows injection moulding to net shape.

Engel sees good potential for components produced by Liquidmetal injection moulding in the field of medical technology, with the parts for the forceps being moulded at the Symposium being a good example, while endoprostheses such as hip joints or stents are also conceivable. Thanks to the excellent mechanical properties of the material, very robust components can also be achieved with very low wall thicknesses.

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