Research On Tool Path Planning And Machining Deformation Of Five-axis Machining Of Free-form Surface

High efficiency and high precision machining of free-form surface is an important research topic of advanced manufacturing field at home and abroad.Free-form surface is complicated and requires high processing quality,and it's usually difficult to machine on 5-axis NC machine tools.Besides,the free-form surface is mostly used in thin-walled parts,which have low stiffness and is easy to produce deformation in processing,and it has bad effects on the accuracy of machining.So,controlling the machining deformation of workpieces plays a role in machining of freeform thin-walled parts with high efficiency and precision.In this paper,blades as the typical freeform thin-walled parts are studied,and the tool path planning and machining deformation are researched,the main contents are as follows:(1)The mathematical theory of cutting force and the mechanics basis of machining deformation are described,the calculation formulae of cutting force are given,also the factors that affect cutting force and the relationship between stress and strain are analyzed.They are provided as the theoretical basis and technical support for this research.(2)The mechanism of residual stress and its influence on workpiece are described,and the X-ray diffraction method is selected to measure the residual stress on workpiece surface.A contrast experiment of thin-walled blades machining is given,the residual stress distribution on workpiece surfaces under zig-zag,contour offset,automatic cycloid and whirlwind tool paths are compared with same cutting parameters.The appropriate tool path for machining thin-walled is selected by comparing the uniformity of residual stress distribution under different tool paths.(3)According to the structural features and technological requirements of the thin-wall blade,also the balance of machining efficiency and machining quality,appropriate process plan of thin-walled manufacture is formulated.The process is divided into four process stages,including rouging,semi-finishing,finishing and clean-up.Besides,appropriate tool paths and cutters are selected for each stage to achieve the high efficiency and high precision machining of thin-wall blades.(4)The causes and control techniques of machining deformation are elaborated,and the contrast experiments with different cutter orientations are designed on the basis of given process plan.The blade surfaces are measured by coordinate measuring machine,and the blade surface error distribution is obtained by comparing with the theoretical model.According to the experimental result,the bending and torsion deformation of blades are analyzed,and an optimal cutter orientation is determined according to the influence of cutter orientations on machining deformation.It can control the machining deformation as much as possible on the basis of interference-free machining of thin-walled blades.