Copper increases efficiency in injection moulding
Replacing traditional steel moulds with those made from copper alloys could make injection moulding of plastic packaging more productive, according to research led by UK-based Copperplas International Ltd.
Sponsored by Eureka, a pan-European network, project Aimtech comprises a consortium of institutions, companies and universities that are keen to enhance the efficiency and competitiveness of European injection moulding in the face of a rapidly developing supply chain in China.
Rex Beechey, Managing Director of Copperplas International, explains that copper alloy moulds have the advantage of being five to six times more thermally conductive than steel, making them suitable for injecting molten plastic at high pressure into a mould.
Beechey says, 'Heat moves more uniformly through copper and at a much greater speed, so it is possible to cool and eject the item being moulded more quickly, saving a considerable amount of time [and avoiding] surface defects such as sinkage and warpage in high volume activity.'
This reduction in cycle time and improvement in finish quality increases the rate of output per machine, raising productivity and energy efficiency, and decreasing capital costs and scrap arising from defunct products.
The team has developed and experimented with two new alloys, comprising around 96% copper with elements of nickel, silicon, titanium and chrome. Numerous industrial trials have confirmed the advantages of using copper alloys to manufacture plastics products of varying types, shapes and thicknesses, and employing a range of different polymers.
Furthermore, the tests have demonstrated how substituting steel for copper alloys has no bearing on the wear, durability or machinability of the mould. 'Plastic is not an aggressive material,' explains Beechey, 'so there is rarely an issue of wear on the surface of the mould.
'Our Danish contact has made 50 million caps and closures, producing 16 cavities at a time, and there was no wear at all.'
An added benefit is copper's recyclability at the end of the moulds' lifecycle. Its status as a refined metal, alongside heightened thermal conductivity, means the material uses less energy in recycling.
The team is now conducting trials with even higher volume production with the aim to move to market. 'Research is moving towards improving the consistency and dimensional statistics of the new materials,' says Beechey. Ultimately, 'the injection moulding industry will be able to, without additional capital investment, reduce cycle time and increase profits'.
Claire Robinson, email: Claire_robinson@hotmail.co.uk.