Printing plastic

Foto:  Sam Rentmeester

Photo: Sam Rentmeester

By 3D printing parts in plastic, scientists are able to conduct much better research on new medical instruments. They are able to print tiny, complex parts simply, quickly and inexpensively.

On the table is a steerable, flexible medical instrument for keyhole operations, which looks like a pair of scissors, due to its handle with two large openings. At the other end, instead of a sharp cutting surface, there is a grasping tool, which can be manoeuvred in all types of curves. The flexibility of the grasping tool is due to its complex shapes. ‘Including gears with tiny flaps and curving channels. These spatial forms are complex to produce’, observes bio-inspired technology professor Paul Breedveld (3mE). He developed the medical instrument in collaboration with PhD student Filip Jelinek. ‘Although it could be made with a machine, that would be very difficult and expensive. This is why we had the idea to make parts with 3D printing’.

That idea was right on target. The parts can be printed for around €100. That is quite a difference from the thousands of euros that Breedveld would have had to spend if they had been produced with a conventional processing machine. ‘We conceive complicated shapes and try to imagine how they work. Now we can print such shapes inexpensively, in order to see whether our ideas are correct.’

It is changing the way in which Breedveld and his colleagues design. He points to the tip of the instrument. ‘On the fifth attempt, everything was in place, and the instrument worked. In the past, when we produced things with a conventional processing machine, we often started big and then kept making it smaller. With 3D printing, we can usually make everything quite small right from the start.’

To produce small prototypes, Breedveld collaborates with several partners, including TNO. The instruments must be ultra-thin if they are to be used by surgeons, and TNO is able to print very thinly with high-quality plastic.

Unfortunately, it is not always robust enough.’ He displays a smaller version of the instrument, that looks like a pair of scissors. ‘I recently dropped this on the floor from a height of one metre. Pieces flew off. Some of the flaps are only 0.3 millimetre thick. We are now exploring how we can print parts that are more robust. We will soon start working with ceramics as well, because we think that it would be stronger than plastic’.

Breedveld emphasises that not every part is suitable for printing. For example, the cables and the turnbuckles are made of metal. ‘In this way, we combine the best of both worlds. We print about 70%; the rest, we don’t print.’


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