Following Ariadne’s Thread through Labyrinthine Voids
The powder bed method of 3D printing makes it possible to create complex metal components that mechanical engineers could only dream of in the past. But after these components have been additively manufactured, there’s often a further challenge: How can the residual powder be removed from the component? Siemens researchers are working together with Solukon, a mechanical engineering company, to develop an algorithm for a cleaning cabin that will enable the powder to be completely removed automatically.
by Hubertus Breuer
Things can get tricky once a metal component has been produced using additive manufacturing. If any powder residue remains, the component, which can cost thousands of euros, could quickly become useless. Yet such components, which often have supportive structures and cooling channels that seem organic, may have powder in their inner structures when they come out of a laser fusion printer after many hours. This residue has to be removed, because after the printing process has been completed, internal structures in such components are still under stress. These stresses are due to millions of microscopic weld seams made by the 3D printing process and are released by a subsequent heat treatment in an annealing furnace. “If the powder has not been completely removed, the residue sinters together inside the component and, in the worst case, makes it useless,” says Christoph Hauck, the Managing Director of MBFZ toolcraft, a company whose products include 3D-printed high-tech components for the aviation industry, medical technology, and other sectors. “If that happens, we not only face financial losses but also a massive delivery problem.”
“The result is nothing less than an improvement to the process chain and a boost to the acceptance of additive manufacturing."
But there’s a good chance that in the future Hauck won’t have to worry about residual powder, thanks to a cleaning cabin from the Solukon company. Solukon, a plant manufacturer specializing in the postprocessing of additively manufactured structures has developed the first solution that uses a digital twin and an intelligent algorithm to completely clean printed components. Thanks to digital construction plans and the known characteristics of the powder, the software combines three-dimensional geometric analysis and particle simulation to calculate how the cleaning machine must rotate, tip or sway the component in order to get the metal powder to trickle out of a 3D-printed part. “The result is nothing less than an improvement to the process chain and a boost to the acceptance of additive manufacturing with respect to productivity and occupational safety,” explains Andreas Hartmann, Managing Director of Solukon Maschinenbau GmbH.
People As Particles
The technology is being first presented to the public at Formnext, the leading trade fair for additive manufacturing, in November 2018. Solukon and Siemens are jointly presenting a prototype. Using a Plexiglas cube, the prototype demonstrates how the powder slides through complex components and finally falls out, thanks to a sophisticated control system. “Simulation is the ideal method to use for such multilayered structures,” explains Christoph Kiener, who came up with this new cleaning idea and tested it extensively in his lab at Siemens. “The decades of simulation expertise accumulated by our mathematicians, combined with the experience of our 3D-printing specialists and other experts from Siemens Corporate Technology, enabled us to tackle this challenge,” he says. “As a result, we were able to solve this tough problem using an agile development process that involved breaking down the problem into less complex work packages.”
The technology is being first presented to the public at Formnext, the leading trade fair for additive manufacturing, in November 2018.
The algorithms of the simulation program calculate a kind of Ariadne’s thread through a component’s labyrinthine voids, along which the powder is led from the interior to the exterior. The powder that lies closest to the exit point is naturally the first to fall out. This clears the path for the powder that follows it. The software simultaneously calculates how the powder that is still inside the component moves in response to every single movement. A team of developers relied on a mathematical procedure that was developed at Siemens Corporate Technology a few years ago for planning emergency escape routes through buildings.
The software, which is equipped with additional algorithms, next calculates the metal powder’s shortest path to the exit point. This sequence of movements is then transmitted to the Siemens controller for the cleaning system. With the help of motors, a swivel device, and a shaker that makes the structure vibrate in a defined way, even a complex labyrinth is completely emptied at the end of the process. “This works for most common geometries, although there are shapes that simply cannot be emptied. Our algorithm would probably still have major problems if it had to deal with the structure of a fish trap,” says Kiener.
This technology is not only innovative. “In view of the cost and effort that was previously required for cleaning additively manufactured parts, it looks as though it will become an essential step in the additive manufacturing of components on an industrial scale”, says Hartmann. Besides, the process saves powder, because the material that has been removed can be reused. “This technology offers only advantages for high-quality 3D-printed components,” says Hauck. “That’s why we too are planning to use this technology.”
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