Modeling And Experimental Research Of Machining Error In Micro Milling Considering Tool Wear

High precision micro parts are widely used in optical,m edical,military,communication and other fields in recent years.In micro milling process,the tool deflection is very significant due to the poor rigidity of micro milling cutter.The workpiece deflection is also significant for the parts of poor rigidity.The deflection of tool and workpiece is directly mapped to the parts surface and forms the machining error.In addition,the tool wear is obvious and the rate is fast in micro milling,which not only makes the cutting forces and deflections increase,but also causes the parts to be undercut and forms the machining error.The machining error caused by tool deflection,workpiece deflection and tool wear seriously reduces the machining precision.The tool wear experiments are carried out in micro milling.The wear morphology and element change of solid carbide micro milling cutter are analyzed in die steel milling.The wear regularities of the micro milling cutter and the effects of cutting parameters and cutting mode on tool wear are analyzed,and the influence of tool wear on cutting force and tool deflection is also investigated.An analytical model is introduced to estimate cutting forces in micro milling with the consideration of tool wear.Based on the analysis of the contact state between tool flank face and processed surface,the tool flank friction force prediction model in micro milling is proposed.Considering the effect of material strain hardening and the edge radius,the shearing force model caused by the shearing action and the ploughing force model caused by ploughing action are established.In addition,considering the influence of tool runout on cutting trajectory,an algorithm including runout is proposed to solve the cutting geometry.The deflection model of micro milling cutter is established on the basis of the cutting forces model and the deformation theory of the cantilever beam.The influence factors of tool deflection as well as the effect of tool deflection on runout are analyzed by utilizing the tool deflection model.A machining error prediction model in micro milling of rigid freeform surface is proposed considering tool deflection and wear.A compensation method for machining error in micro milling of freef orm surface is developed by using the multilevel iterative algorithm.The effects of thin wall design thickness,tool rigidity,milling mode and cutting parameters on the machining error in mico milling of thin wall parts are investigated through a series of experiments.According to the experimental results,the optimization of parameters in micro milling of thin wall parts is presented.Based on the research of the machining error in micro milling considering tool wear,tool deflection and workpiece deflection,a good theoretical and technical support is provided for micro milling of rigid freeform surface and thin wall parts.High precision micro milling is realized.