Smooth Geometry Generation in Additive Manufacturing File Format: Problem Study and New Formulation

Purpose: In the newly released ASTM standard specification for Additive Manufacturing File (AMF) format – version 1.1, Hermite curve based interpolation is employed to refine input triangles to generate denser mesh with smoother geometry. This paper studies the problems of constructing smooth geometry based on Hermite interpolation on curves and proposes a solution to overcome these problems. Design/methodology/approach: A formulation using triangular Bézier patch is proposed to generate smooth geometry from input polygonal models. Different configurations on the boundary curves are analysed to further enrich this formulation. Findings: The formulation given in the AMF format (version 1.1) can lead to the problems of inconsistent normals and undefined end-tangents. Research limitation/implications: The proposed scheme has requirements for the input normals of a model, only C 0 interpolation can be generated on those cases with less-proper input. Originality/value: To overcome the problems of smooth geometry generation in the AMF format, an enriched scheme is proposed for computing smooth geometry by using triangular Bézier patch. For the configurations with less-proper input, the Boolean sum and the Nielson’s point-opposite edge interpolation for triangular Coons patch are used to generate smooth geometry as a C 0 interpolant.