Quality Evaluation And Parameter Optimization Of High-pressure Abrasive Waterjet Planar Milling

Abrasive waterjet process is a special machining method using high-speed waterjet to accelerate abrasives and remove workpiece materials erosively.It has unique characteristics of small cutting force,nearly zero thermal influence,versatility for brittle and ductile materials and so on.Compared with traditional machining method,it has the advantages of low cost,high material removal rate and good machined surface quality.For titanium alloy siding parts which are widely used in aerospace industry,abrasive waterjet milling has good adaptability which not only meets the requirements of high material removal rate,but also reduces the workpiece deformation to a great extent.The abrasive waterjet milling can be seen as an alternative method for this kind of parts.Abrasive waterjet milling is an emerging hot spot of special machining in recent years.Through the comprehensive control of machining parameters such as water pressure,traverse speed,stand-off distance,abrasive flow rate,track spacing,etc.,the pattern and depth control of the machined surface can be realized.However,performance fluctuation of the abrasive waterjet and environmental disturbance are not conducive to the depth target and milling quality of the machined surface,which makes the milling surface appears defects such as stripes,pits and irregular fluctuations.In order to improve the milling quality and reduce the defects,this paper studies the milling law by means of experimental research and data analysis,puts forward the method of parameter optimization,and provides theoretical and technical basis for industrial application.In this paper,the generation process of abrasive waterjet and the removal process of plastic materials are introduced.It is shown that there is a fluctuation of jet machining energy in the whole process of machining,which will cause a specific series of pattern on the machined surface.The range of abrasive waterjet impact force on the workpiece is predicted as well.The single-factor experiments and orthogonal tests are carried out by the method of single-linear milling.The influence rules and order of process parameters on jet machining ability are obtained.The method of contour screening which can be applied to plane milling is put forward.The response surface method with Box-Behnken design is used in plane milling experiment with parameters falling in the optimized range.The average milling depth and the height of surface peak-and-valley(P/V)are proposed as the evaluation criteria of milling quality.The qualitative and quantitative research of single factor and their interaction is carried out for each parameter.According to the experimental results,Buckingham's theorem is used to perform regression analysis of the average milling depth and the establishment of a semi-empirical model.It can be used to predict the machining results within the experimental range after data validation.At the same time,guided by the average milling depth,the machining parameters can be assigned according to the influence degree of machining ability of the abrasive waterjet guided by the model.Based on the existing milling data,it is proposed that the selection of milling parameters can follow the material-removal-priority strategy and the surfacesmoothing-priority strategy.On this basis,multiple attempts to mill the same position have been tried to verify the superposition of the average milling depth.Finally,an arrangement strategy is proposed for several typical planar milling trajectories,and a milling experiment is carried out on the complex planar pattern with different milling depths by using the processing parameter selection method described in this paper,which verifies the feasibility of parameter optimization and trajectory arrangement strategy.