3D printing: precise simulation of molten metal
3D printing of metal involves melting metal powder using a laser. This can cause individual areas of the part being created to deform if they become too hot. Siemens researchers are now simulating the heating process to prevent this deformation, and are making an important contribution to the industrial implementation of 3D printing.
Omar Fergani, Director of Strategic Business at Siemens Digital Industries, explains: “Our goal is to get component manufacture right first time. Previously, localized overheating would compromise the printing process or the shape of the component. Our research team is adopting a new approach to help prevent this problem, which will take us a step further in the development of a new 3D printing module for the software from Siemens Digital Industries, known as ‘AM Path Optimizer’ (AM = additive manufacturing).”
Source of problems: Overheating in the printing process
Daniel Reznik and Katharina Eissing work on process simulation for additive manufacturing at Siemens Corporate Technology. “We are looking at the question of overheating with powder-based additive manufacturing because it can compromise both the process and the product,” Reznik explains. As the laser follows programmed tracks over the powder, it melts specific small areas, forming a molten metal bead, which builds up the shape of the desired component as it cools. Eissing explains: “Sometimes, however, the laser beam passes right alongside an area that has not quite fully cooled, causing it to overheat. A larger area melts as a consequence, and the bead becomes not only wider but also higher.” The result is a raised area on the component, which can lead to a number of problems: The component will not have the desired shape, a subsequent coating process is made more difficult, or the printing process may even be interrupted because the blade that continuously moves a thin layer of powder across the component becomes caught on the raised part.
Handy tricks: Simulation with shortcuts
Production engineers would therefore like to know in advance if their component can be correctly printed using the intended process. The team of researchers therefore simulates the process and resorts to a trick to keep the cost and effort within reason. Eissing explains: “In an ideal situation we’d calculate the heat distribution at every individual point exposed by the laser. But that would take years, even with the most powerful computer. That’s why we derive a thermal model from a number of simulations of selected sections that are typical of the process using machine learning. This model can then be applied to the entire component. If we identify a risk of overheating, we can correct the laser path, for example. This is where it’s critical to weigh up the balance between higher quality and additional time spent on the printing process.”
Future product: AM Path Optimizer
Based on these activities, the development team headed by Tom van ‘t Erve at Digital Industries is now creating a further Siemens NX module for additive manufacturing. Van ‘t Erve integrates the simulations into the existing NX Software for the construction preparation stage, enables graphic representation of overheating patterns, and adapts the software for 3D printers from all relevant manufacturers. He comments, “Our co-workers at Corporate Technology have provided the ideal basis for a product that has generated a lot of interest among our customers.” Although the AM Path Optimizer software is expected to be commercially available about a year from now, van ‘t Erve already has plans for expansions. “We are aiming to offer our customers a database containing process information from prepared simulations for all standard printed materials, give them the opportunity to outsource the computer-based simulations to us, and let them decide for themselves whether their priority in the manufacturing process is speed or quality. That will take us a step further in the industrial implementation of 3D printing.”
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