An empirical study of parameters in abrasive jet machining

Abstract

Abrasive jet machining (AJM) is a process that removes material by directing a high velocity stream of abrasive particles onto a workpiece. This paper reports a study of the results of machining under various conditions. A commercial AJM machine was used, with nozzles of diameter ranging from 0.45 to 0.65 mm, the nozzle materials being either tungsten carbide or sapphire, both of which have high tool lives. Silicon carbide and aluminium oxide were the two abrasives used. Other parameters studied were nozzle tip distances (5–10 mm), spray angles (60° and 90°) and pressures (5 and 7 bars). The materials machined were glass, ceramics, and electro-discharge machined (EDM) die steel. Material removal rate and the machined cavity dimensions were measured. The blind holes that were drilled were found to be not circular and cylindrical but almost elliptical and bell mouthed. High material removal rate conditions did not necessarily yield small narrow clean-cut machined areas, a desirable factor for AJM applications. Empirical evaluation was carried out to characterize quantitatively the effects of various machining conditions. During the course of these investigations a red hot region was found to form under certain conditions and accompanied by high material removal; a metallurgical study of this red hot zone and its relation to optimum AJM machining conditions are presented.