Physician, reshape me

Rapid prototyping technology could soon be making its debut in dentistry and hospital surgery. Damon Schünmann reports.

Rapid prototyping technology could soon be used to produce medical implant-quality components if the German authorities approve their use in humans. The fast-developing technology is on the cusp of spawning a new age in industrial manufacturing as science fact catches up with science fiction.

While acrylic polymers are already being used in rapid prototyping machines to create 3D models from CAD images, the move towards rapid manufacture of functional metal components is gathering pace. The US military is already using the LENS process to repair helicopter components in combat theatres. Now German designers from the Fraunhofer Institute for Laser Technology are using technology developed alongside German engineering giant Trumpf to manufacture dental prostheses. BEGO Medical AG is already in place as a test customer.

The main advantage of this kind of manufacture is that components can be made overnight compared with weeks using traditional methods. The process, known as direct laser forming, uses a single-component metal powder as the build material. Layers of powder are injected in lines, side by side, and micro-welded by a diode pumped solid-state laser. Once complete, each layer has a thickness of 30-100 microns and a density of almost 100 per cent. The results are similar to the products created by conventional casting.

Researcher Dr. Christoph Over compared the new device with LENS: ‘We have the objective of creating complete new parts independent from existing parts. LENS is more focused on modifications of existing parts.’ He explained that although LENS can be used to manufacture individual components, it has geometric limitations producing intricate shapes and overhanging structures. Such overhangs are more easily tackled with the Trumpf machines because there is a layer of powder underneath.

However, LENS does have some advantages. Repair work on existing materials is not possible with this model of the German device and it cannot be used for work requiring the composition of more than one material. But Trumpf claimed it is currently developing a machine, the Trumaform DMD 505, that will be able to perform repair and modification work just like LENS.

‘In comparison to other metal processing layer by layer [generative technologies], we have the most advanced knowledge regarding different materials and are closest to an industrial machine,’ said Dr. Over.

His team has carried out innovative work using nickel and aluminium alloys as well as the more commonly utilised titanium and steel.

Trumpf is currently negotiating with German companies that are interested in using its tools for injection moulding. Project manager Dr. Joachim Hutfless said: ‘We have concentrated on qualifying tool steel and stainless steel so the machine will be ready for sale.’ He added that the first commercial deliveries are anticipated for this summer.

The next big step for the technology is the manufacture of medical implants in Grade II (or ‘commercially pure’) titanium. Typical components could be used for facial reconstruction and hip joints.

Although such an enterprise will be dependent on health authority approval, it is hoped that metallic rapid prototyping techniques will be used in this capacity within two years.