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Simufact: Sintering simulation for BJT
Simufact Additive: Accelerating the metal Binder Jetting workflow with sintering simulation The ability to 'design out' distortion during sintering is seen as key to enabling the faster commercialisation of metal Binder Jetting (BJT). The Simufact Additive software platform, now on the third release of its BJT sintering module, is able to accurately simulate the sintering process, predicting shrinkage, slumping and friction-related distortion, either with or without 'live' and 'ceramic' setters, resulting in a downloadable 'compensated' component geometry to be fed directly to the AM machine. In this article, Jeff Robertson explores through case studies how The ExOne Company has been using the software in its AM adoption and R&D centres to optimise customer parts for sintering.
While the manufacturing industry has been successfully sintering parts formed with bound metal particles for volume production through the Metal Injection Moulding (MIM) process since the 1980s, newcomers to sinter-based AM processes such as Binder Jetting now want a fast and easy digital manufacturing solution more in line with the Additive Manufacturing mindset. Both MIM and BJT parts are created with ultrafine metal powders, usually in the 10–30 µ m range, and binders, with BJT using far less binder than MIM. In MIM, this pre-blend of powder and binder is shot into a mould. In BJT, the binder is jetted onto a layer of loose powder, layer by layer, until the final shape is created. In both processes, the green parts created from the bound powder must then be debound and sintered at just below the melting point of the metal powder until the particles are successfully fused to the desired density. In order for metal Binder Jetting to realise its full potential as a highspeed, low-cost metal AM process for complex designs, it is widely
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acknowledged that the sintering process must be effectively managed. At ExOne, BJT can now reliably deliver final parts with high densities of 97+% for a wide range of metals, as well as dimensional accuracy of 1–2.5% on the first build, with even better results of less than 1% after a design has been optimised for the process (primarily sintering). Despite
the ability to build and sinter BJT parts consistently, the challenges associated with large amounts of shrinkage and distortion still remain. Until recently, however, MIM and BJT experts have relied solely on their experience and iterative trial-anderror processes to nail down a final design that could be transitioned to high-volume production. This often
Fig. 1 Simufact Additive has been a class leading solution provider for metal Powder Bed Fusion (PBF) process simulation since its release in 2016. Here, predicted distortion of a turbo-pump housing built on a large format (400 mm) machine is shown
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