Suitability of Eroded Particles from Die-Sink Electro Discharge Machining for Additive Manufacturing—Review, Characterization and Processing

Abstract

In this bipartite study, waste products of die-sink electro discharge machining (die-sink EDM) are investigated. EDM is based on an erosive character of discharges leading to material removal and molten material congeals in the dielectric. The aim is to show a theoretical suitability of these particles for a further usage as a secondary, recycled material in additive manufacturing (AM). Due to the energy- and cost-intensive process of gas atomization for AM powders, there is a need for alternative concepts for particle generation. The first part deals with an intensive review of references from the literature regarding particle size and circularity using image analysis. Secondly, real waste streams were investigated after washing and cleaning processes for oil removal via laser diffraction, dynamic image analysis, SEM with energy dispersive X-ray spectroscopy (EDX) as well as optical emission spectroscopy (ICP OES), categorized within the literature and compared to commercial AM powders. In general, it could be shown that, in principle, recycled particles fulfill main requirements for an AM usage regarding size and shape. Reference powders show median particle sizes of 30 µm to 34 µm and circularities of 0.90 to 0.93, whereas eroded particles exhibit an x50 value of 27 µm and circularity of 0.90, too. However, chemical purity, mainly caused by carbon contamination (5.4 wt% in eroded powder compared to 0.4 wt% in reference powder), must be improved before printing via AM machines. Additionally, several separation techniques have to be applied to remove undesired elements (alumina).