Comparison of dimensional tolerance grades of AM systems

Every manufacturing process allows fabricating a product with some dimensional and shape errors from the ideal nominal geometry. For this reason, on the product blueprint engineers indicate the admissible tolerance interval for critical dimensions. Unlike traditional manufacturing processes, no tools, molds or dies are needed in additive manufacturing (AM), so a single machine can produce an infinite number of different shapes. In a single operation, an AM part is built layerwise and often net shape, that is no finishing operation is carried out to change its dimensions apart from some sandblasting or polishing required to reduce superficial roughness. It is therefore fundamental to know in advance the dimensional tolerance for AM processes but currently little information is available in the literature. In this paper, a benchmarking analysis is carried out among three different AM systems for polymers and their dimensional accuracy is defined using the ISO IT grades of a reference artifact.