By Aad van de Wijngaart
What’s it like to use 3D printing for critical applications? That’s what Paul Breedveld discussed in a full Hive room during the 3D Print Week. As a professor at the BME department, he researches endoscopes that can be bent precisely around organs. That’s handy, because then a small hole suffices for taking biopsies and other medical actions.
Such an endoscope had already been introduced by others. This EndoWrist however can only be bought as part of a two million dollar operation robot. And after just fifteen operations it must be sent back to the factory, because of fatigue in the little steel cables that are used to bend it.
Breedveld thought ‘I can better that’. He took inspiration from nature, in the shape of the octopus arm. To copy its workings, he looked into alternative, more complex connections for the segments of his endoscope. And it turned out that they could only be made with 3D printing.
That was the start of Breedvelds journey of discovery through the world of ‘additive manufacturing’. Naturally, he wanted his endoscope to be as thin as possible. Via TNO in Eindhoven he got his hands on a resin that was filled with a ceramic substance and that could be printed with a resolution of 30 micrometer. The result felt great: strong, yet slightly flexible.
But when, half a year later, the instrument accidentally fell on Breedvelds carpeted office floor, it broke in two. The cause was soon discovered: the material slowly but steadily kept hardening after it came out of the printer. Therefore it became ever more brittle.
The next attempt was with an extremely hard polymer, 5 mm thick, at 75 micrometer. But this, too, turned out to be very brittle. Even worse: it would warp during printing. Breedveld started to lose his enthusiasm for this new technology.
But he kept trying, this time teaming up with a new printing company and a new, strong material. This turns out to have another defect: it shrinks. So the design must be adjusted to the printing process. It’s this stage of trial and error that occupies Breedveld and his staff at this moment.
Based on his experiences, the Delft professor regards 3D printing as just another technology that may be used in the making of instruments. Preferably for parts that are not too small.
He sums up the problems that plague 3D printing for now. Printed metals are too rough and imprecise. So are resins, and they are also have problems of shrinkage and warping. If the objects are small, it’s a pain to remove support material. And last but not least, it’s vital to keep close contact with the printing people. “You can’t simply order something and trust that it will fit. That was new for us.”
But sometimes, 3D printing is really the only way to make something that he needs. And Breedveld loves the ease of printing prototypes fast and often. “Printing takes the place of thinking. That makes it extremely useful.”