Pressure Effects in Abrasive-Waterjet (AWJ) Machining

Abrasive-waterjets (AWJs) are formed by mixing high-pressure (up to 400 MPa) waterjets (0.1 to 1 mm in diameter) with abrasive particles in mixing tubes with typical 1/d ratios of 50 to 100. The pressure of the waterjet influences the overall performance of the abrasive-waterjet cutting system through operational and phenomenological effects. Higher pressures result in lower hydraulic efficiency, more frequent maintenance, high wear rates of mixing tubes, and fragmentation of particles before they exit the nozzle. However, with high pressures, deeper cuts can be obtained and higher traverse speeds can be used. Consequently, the hydraulic power is best utilized at an optimum pressure, which is a function of all other parameters as well as the application criteria. This paper presents data and analyses on the effect of pressure on nozzle operational characteristics, i.e., jet spreading characteristics, abrasive particle fragmentation, suction capability, wear of mixing tubes, and mixing efficiency. The effect of pressure on the parameters of cutting performance is discussed with example data. These parameters are depth of cut, specific area generation, maximum cutting traverse rate, surface waviness, and cost of cutting. Optimal pressure examples presented in this study indicate that pressures over 240 MPa are required for efficient abrasive-waterjet performance in metal cutting.