Tensile strength in FFF
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How build parameters influence the tensile strength of 316L parts produced by Fused Filament Fabrication In this article, Dr Samuel von Karsa-Wilberforce, Emery Oleochemicals, Germany, and co-authors report on the tensile strength of sintered 316L specimens produced via Fused Filament Fabrication (FFF), a Material Extrusion (MEX)-based Additive Manufacturing process. The parameters studied include printing nozzle temperature, flow percent or extrusion multiplier and nozzle diameter of print head. The 316L feedstock filaments are based on Emery Oleochemicals’ evolutionary binder system, which has been used in MIM for more than thirty years. The partner in the study for debinding, sintering and mechanical testing is CMG Technologies Ltd, UK.
Widely known metal Additive Manufacturing processes such as Laser Beam Powder Bed Fusion (PBF-LB) are expensive and generally energy intensive [1]. More recently, the Additive Manufacturing of metal parts via Binder Jetting (BJT), typically using MIM grade powders, has also come to the fore. However, metal Binder Jetting machines are usually quite expensive, and the additively manufactured green part may be prone to breakage if not carefully handled. In comparison, Material Extrusion (MEX) processes such as Fused Filament Fabrication (FFF), also known as Fused Deposition Modelling (FDM), are cheap, and the processes' low energy consumption offers the potential to produce functional metal parts at low cost [2]. FFF machines are more readily available and easier to operate than conventional metal AM machines. Metal FFF uses a highly filled polymeric filament containing more than 90% by weight metal powder to create ‘green’ metal parts, which then go through debinding and sintering steps to produce
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metal parts that are close to fully dense. The process of using FFF to produce metal parts from sinterable feedstock is described in detail elsewhere [1]. While the economic and technological benefits of producing metal parts via FFF are clear, it is essential to investigate the mechanical properties of the resulting parts in order to select meaningful and suitable application areas. It has been reported
that the mechanical properties of FFF plastic parts are highly dependent on the build, or printing, parameters due to the anisotropic nature of the FFF process. Typical build parameters that highly influence the mechanical properties of FFF parts include printing nozzle temperature, z-direction layer thickness, printing speed, print nozzle diameter, extrusion multiplier or flow percent, infill pattern and infill density [3].
Fig. 1 316L feedstock filament, 2.85 mm diameter
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