Investigation On Machined Surface Quality In High-Speed Ball-end Milling Of Mold Steel

High-speed ball-end milling is widely used in the field of the molds and dies manufacture, the mold surface quality relates to product quality and mold life. The nature of the mechanism of high-speed ball-end milling surface summarized as follows: Unbalanced periodical milling force and temperature field affected on the elastic-plastic materials surface, which produced elastic recovery and the deformation of machined surface, and changed the features of the workpiece geometry precision and mechanical properties for the machined surface layer.Cutting parameters and tool orientation parameters infuses the residual stress, surface roughness and hardness layer features in the high-speed ball-end milling process of machined surface. The research of surface quality integrated analytical, simulation and experimental methods to study surface quality prediction, optimization and control. It put forward new ideas and new methods to develop new algorithm to meet the needs of production practices.According to the characteristics of high-speed milling, based on the metal cutting theory, this paper modeled the cutting force of ball-end mill. The variation behavior was analyzed. Combining with the tool orientation and trajectory characteristics of the ball-end milling, the relationship between cutting forces and machining parameters (tool orientation, spindle speed and so on) was researched experimentally. The influence mechanism and rules of machining parameters on cutting forces were revealed.Based on characteristics of high-speed ball-end milling, this paper studied ball-end milling surface residual stress, surface morphology and the formation of hardness layer elastic-plastic materials features, revealed the high speed ball-end milling mechanism of the surface deformation.Through measuring the residual stress of machined surface of high speed ball-end milling based on non-destructive measuring method, the cumulative effect of surface residual stress was found in the tool path direction. The effect mechanism between machining parameter and residual stress was studied under multi-axis CNC machining conditions, generation mechanism was studied and theoretical hypothesis was proposed. The relationship between tool oritentation and surface residual stress was revealed. The fitting polynomial formula of surface residual stress and cutter inclination angle was modeled. According to the experimental results of milling HI3, the paper established analytical prediction model of surface residual stress under high-speed milling conditions, the inclination angle and roll angle are two important influence parameters. A simple model was deduced on momentum theorem. It gave the final optimized result by using the model.Experiment studied comprehensively the effect relations of machined parameters and the surface qualities in ball-end milling. According to a single factor experiments and multi-factor testing, the paper revealed the law of cutting parameters on surface quality by modeling the relational model based on experimental results, it further studied the mechanism of surface quality under the various factors with the quantitative analysis method.Based on the experimental research and influence mechanism results of cutting parameters on surface quality, the multiple linear regression prediction models for the influence of radial width of cut, axial depth of cut, feed per tooth, the inclination angle, roll angle on every form of surface quality was modeled. The paper gave a new method by combining advantages with the multiple linear regression and artificial neural network, it was named MLBP, and the MLBP prediction model is established by means of interpolation theory. The model was proved feasibility and robustness with the high prediction accuracy.Based on the development of mechanism and prediction method of surface quality for high-speed ball-end milling, integrated system software with the ability of second development for prediction of surface quality was developed. The application and promotion of the software brought the enormous social and economic benefit to enterprise.