Though there is a lot of talk of 3D printing bespoke medical implants one of the few factors preventing the widespread adoption is the surface finish.
Though complex, bespoke skeletal joints are now possible with current technologies, the strongest materials must be used particularly for the likes of heavily used knee joints.
The Universtiy of Sheffield Advanced Manufacturing Centre (AMRC) with Boeing want to use cobalt-chrome metal powder to make artificial knee joints but have become frustrated by the lack of surface finish quality when 3D printed.
The answer it appears comes in the shape of a huge ROFIMAT MC607, 5-axis CNC grinding machine, made by German company Blohm Jung, which has been supplied by Blohm Jung’s UK agent, JRA Bennett.
“The big advantage is the joint is bespoke, so you are replacing like for like and 3D printing saves on material, so there is the potential to reduce weight,” says Dr Andy Bell, from the AMRC Design & Prototyping Group.
“However, the surface isn’t of a high enough quality for components used in a replacement joint, so it has to be very, very highly finished, which is where the grinder comes in.”
Initially, one of the grinder’s key roles will be understanding how additive manufactured parts behave during grinding. The machine is one of the most flexible machines of its type and has been installed at the AMRC Design Prototyping and Testing Centre.
Its 24-position tool magazine can hold mills, drills and other cutters, as well as grinding wheels up to 400 mm in diameter and 100 mm wide.
That allows the number of separate machining operations to be reduced, often to just one, cutting manufacturing costs and, when combined with the eight tonne machine’s increased rigidity, increasing accuracy.
The machine also boasts significantly higher positioning speeds and a wheel cleaning system that helps to keep grinding wheels sharp, while maintaining their profile, allowing increased feed rates.
