Novel methodology for burr extension estimation on machined SLM surfaces

Additive manufacturing techniques can cover the needs of these components thanks to their high level of customization of the products and the ability to realize complex shapes without high effort. Despite the benefits derived from AM processes, these techniques are characterized by a low-quality of surface finish, one of the most important requirements for medical devices. Considering this aspect, it is important to develop a solution able to improve the surface finish in order to enjoy the low lead times and the high level of customization typical of these processes. A characteristic element of micro-machining is the presence of burrs on the machined surface which can affect the surface texture of micro-features. For this reason, a novel technique for the evaluation of burr was defined. The burrs were evaluated by means of an autofocus variation digital microscope Keyence VHX-7100, on 17-4 PH steel samples produced by laser bed fusion. A 3D reconstruction of the channels and holes surfaces was performed and through the analysis of the peaks distribution, a threshold was defined to discriminate between the original surface of the part and the burrs. In this way, it was possible to estimate and approximate the value of the extension of the burrs in terms of volume and area, where the area is referred to the projected area. Specifically, in micro-machining, not only the extension of the burrs is significant, but also the variability is particularly high, preventing a priori consideration of the defect.