Characterisation of High Speed Sintering Surface Topography with Re-entrant Open Surface Pores using 3D Surface Texture Parameters and Material Ratio Curve

High Speed Sintering (HSS) is a polymer powder bed additive manufacturing process for economical volume production of end-use parts. The surface of HSS components often contains 3D features, e.g. re-entrant open surface pores. X-ray computed topography is capable of capturing these features, allowing measurement data to be used for surface texture characterisation. This paper focuses on characterising HSS surface topography based on the newly developed 3D surface texture parameters with a special interest in the re-entrant surface pores. In comparison to the conventional areal counterparts, the 3D surface texture parameters pioneered in this study have been proven to be able to fully characterise re-entrant features, and thus better reflect the 3D nature of HSS surface topography. The selected three 3D height parameters (i.e. Sa, Sq and Sv) and the three 3D hybrid parameters (i.e. Sdq, Sdr and Srf) are useful to quantify re-entrant open surface pores from different perspectives, e.g. variation, depth, gradient, area. The material ratio curves of HSS surfaces vary in their shapes and display recess shapes at the surface heights where the re-entrant pores start to build up. Furthermore, the volume parameter Vvv is utilised to characterise the volume density of open surface pores.