Abrasive waterjet micro-machining of channels in metals: Model to predict high aspect-ratio channel profiles for submerged and unsubmerged machining

Recent advances in the development of miniaturized nozzles have made possible the use of abrasive waterjets to perform controlled-depth micro-milling. Haghbin et al. (2015) discussed the effects of the surrounding fluid in the micro-machining of shallow channels in 316L stainless steel and 6061-T6 aluminum using a prototype nozzle having an orifice diameter of 127 μm and a 254 μm mixing tube diameter. This paper uses those results to develop a new surface evolution model that predicts the size and shape of relatively deep micro-channels resulting from unsubmerged and submerged abrasive water jet micro-machining (AWJM). For both unsubmerged and submerged AWJM, and for both materials, the erosive efficacy distribution changed suddenly after the initial formation of the channel. The initially wide distribution was due to backflow of the abrasive slurry along the channel walls, which did not occur once the channel was formed and most of the flow was directed along the channel length. A novel approach in which two different erosive efficacy expressions are sequentially used in a surface evolution equation is presented and shown to accurately predict the evolving surface topography for micro-channels up to aspect ratios of 3.