| Large titanium alloy structural parts are the main parts of aircraft body frame,so the machining accuracy is required.End milling cutter is the main tool for machining titanium alloy structural parts.In the milling process,due to the influence of cutter tooth error,vibration,cutting edge wear and other factors,the distribution of geometric errors on the machining surface along the cutter feed direction is diverse.Therefore,it is of great significance to study the formation mechanism and distribution characteristics of machining errors in milling process.Based on the national natural science fund project "efficient milling kinetics of nonlinear friction wear multi-scale coupling mechanism(51875145)" and the chengdu aircraft industrial(group)co.,LTD enterprise cooperation project "large titanium alloy structure precise control technology" the milling tool life support,carry on the processing error of the study of the formation process and its control method.In order to reveal the variation characteristics of machining errors on the surface of titanium alloy workpiece,a solid carbide end mill with a diameter of20 mm was used to conduct the milling experiment of titanium alloy,and the milling surface of titanium alloy under the influence of milling vibration,cutter tooth error and cutting edge wear was obtained.According to the CMM results of the machining surface and the national standard GB/1182-2008,the geometric errors of the milling surface were calculated by the three-point method.The shape,position,dimension error of the local area of the machining surface at different positions were obtained along the feed direction of the milling cutter with the method of equidistant distance,and the variation process of machining error of the milling titanium alloy was revealed.The geometric error distribution function of machining surface was constructed by using themethod of binary polynomial fitting,and the variation characteristics of machining error in milling titanium alloy were quantitatively described.And the influence characteristics of cutter tooth error,cutting edge wear and milling vibration on milling error are analyzed.The influence models of cutter tooth error,cutting edge wear and milling vibration on the milling surface were established.In order to reveal the formation process of machining error,under the tooth error and the milling vibration,the cutting motion reference system of the end milling cutter and tooth was established.The instantaneous cutting motion relation between workpiece and cutter tooth was revealed and the calculation method of the cutting motion trajectory and instantaneous cutting position angle of tooth was proposed.Studying the dynamic formation process of the machining transition surface,the computational model of the formation process of geometric error on machined surface was established and the dynamic characteristics and control variables of the formation process of machining error was revealed.Combining simulation examples and experimental results,the effectiveness of the model was verified.In order to reveal the influence of milling vibration on machining error,adopting the integral carbide end milling cutter with a diameter of 20 mm and radial stratification cutting method,the vibration experiment of milling titanium alloy was carried out.Obtaining the time domain signal of milling vibration in multi-layer cutting,the variation characteristics of milling vibration is analyzed along feed direction,cutting depth direction and cutting width.Adopting the geometrical error formation process on the machined surface,the distribution characteristics of machining error along the feed direction were studied under the milling vibration.Through the correlation analysis among milling vibration time domain characteristic parameters,the machined surface shape error,the position error and the dimension error,the influence of milling vibration on the formation process of machining error is revealed.Aiming at the technological requirements for milling large structural parts of titanium alloy,the evaluation model for the consistency of machining error distribution was established,with the variation characteristics of machining error formation process in milling titanium alloy.Based on the calculationmodel of the geometrical error formation process on machined surface,the influence of tooth error,cutting parameters and cutting edge wear on machining error and its distribution were analyzed.The process design method for milling titanium alloy was proposed with end milling cutter.According to simulation examples,the process design plan was evaluated. |
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