Shrinkage evaluation and geometric accuracy assessment on 17–4 PH samples made by material extrusion additive manufacturing

Material Extrusion Additive Manufacturing (MEX) is one of the most common Additive Manufacturing (AM) technology. The possibility to realize metal parts using this technology has several advantages and generates great costs reduction with respect to other metal Additive Manufacturing technologies. However, there are some disadvantages related to the design and production of these extrusion-based metal parts, especially when considering the fabrication of complex geometries. One of the main problems is related to the oversizing of the parts due to the shrinkage phenomenon occurring after the debinding and sintering steps. In this work, a comprehensive study about the shrinkage phenomenon was conducted on 17–4 PH stainless steel parts realized via MEX, analyzing the influence of printing and sintering orientation, infill strategy and aspect ratio. With this aim, by using the Design of Experiment approach, samples were analyzed in both as-printed and as-sintered conditions. Shrinkage percentage values, geometric accuracy and density were the main investigated outputs. A commercial 3D structured-light scanner was used to collect the dimensional and geometric data. Results showed a strong shrinkage anisotropy, more relevant for samples with different orientation during the printing and the sintering phase. Geometric accuracy, in terms of flatness, was also assessed comparing green and sintered parts.