A BREAKTHROUGH by researchers from South Yorkshire could challenge an American stranglehold on the production of hi-tech castings for safety critical applications.
Developments by Advanced Manufacturing Park-based Castings Technology International have opened the way to creating castings weighing several tonnes, from a range of standard and exotic materials which may need little or no machining before being put into service.
Cti’s technology is based on the ‘Replicast’ technique it developed some years ago to make moulds for smaller castings and prototypes and is ideally suited to meeting market demand for one-off and low volume castings, made to short lead times.
Two American corporations currently have a virtual monopoly on making large castings for the aerospace industry and some other applications thanks to major investment by the US military.
Cti has been forced to proceed more slowly, funding its developments internally, with no help from government, but now it has scaled up the Replicast process so that it can be used to create moulds that are up to two metres square, allowing castings weighing several tonnes to be made.
Cti’s technology is based on the centuries old lost wax method of making castings, where a ceramic shell is built up around a wax replica of the item being cast.
However, unlike the American duo that dominate the market and use wax, the Sheffield research centre builds ceramic moulds around patterns precision machined from polystyrene blocks, cutting the need for expensive tooling, explains Cti’s chief executive, Dr Mike Ashton.
As with the lost wax process, the polystyrene disappears when the ceramic is fired.
Cti’s new MEGAshell development offers additional benefits, allowing heavy castings to be made which are 20 per cent lighter than those made by the current sand casting method, cutting machining costs by 50 per cent or more. Cti says its MEGAshell technology has been shown to be able to meet the market demand for large, near net shape castings, especially in costly alloys of steel and nickel and it has now refined the technology so that it can be used for reactive alloys of titanium and zirconium.
Dr Ashton says Cti is talking with potential users of the technology in the Sheffield City region and working with a company from the power generation sector to perfect the technique for components in nuclear power stations.
The same technology could be developed for use in aerospace, but Dr Ashton sees that as a longer term aim because of the high cost of gaining acceptance for new techniques for making components in that sector.