Jan 23, 2019 | By Cameron
A team of researchers at TU Delft has further optimized the process of 3D printing graded microstructures. A lot of minds are working on this problem because graded densities make for an incredibly efficient use of mass. Bones are a great example: a bone’s density is higher where the bone endures more strain and lower where it bears less weight. As a result, the bone has a high strength-to-weight ratio and is rigid where it needs to be while also being more flexible at other points. That change in density is a microstructure gradient, and it’s found all throughout nature, but 3D printing those gradients has proven difficult.
The main obstacle to fabricating microstructure gradients is matching the compatibility of adjacent unit cells; the microstructures have to physically connect with each other, but with differing densities, their geometries don’t necessarily align well, meaning some unit cells won’t be touching the adjacent unit cells of a differing grade. This creates structural integrity issues that can cause problems during and after a 3D print. The solution is mostly computational and algorithmic because the best 3D printing hardware can produce pretty much any geometry. The trick is creating that geometry.
The TU Delft team sought to “find the optimal connectivity between topology optimized microstructures.” And they did. Their method “simultaneously optimizes the physical properties of the individual cells as well as those of neighbouring pairs, to ensure material connectivity and smoothly varying physical properties.” They demonstrated their method by 3D printing an implant prototype where the central region is very dense but gets gradually more porous towards the exterior of the part. The “functional gradation promotes bony ingrowth at the bone-implant interface, while maintaining structural integrity and increasing the mechanical properties in the areas where bony ingrowth is irrelevant.”
The researchers’ graded microstructure optimization process will serve the medical and aerospace industries well, where the lightweight performance will be most appreciated. Eventually, these density gradients will be added as a feature in either 3D modeling software or slicing programs, or both. Designers will be able to select a starting point, an ending point, and a gradient range and direction, just like in Photoshop, and then 3D print an object with a density gradient. The question is, who will implement such a feature first?
Posted in 3D Printing Application
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