Research On Compensation Algorithms Of Ball-end Milling Cutter For5-axis Freeform Surface Machining

The rise of manufacturing industry in our country and the constant advanceof the related technologies lead to an ever-increasing demand on the performanceof high-end NC (numerical control) machine tools; nonetheless,5-axiscoordinated NC machine tools, with prominent advantages, are extensivelyapplied to the processing of complicated curved surface. As an importantindicator of5-axis NC machine, processing precision can be affected by manyfactors and thus is becoming the focus of research. Among other things,processing precision can be improved by three-dimensional cutter compensationtechnology; therefore, an in-depth study on the issue of cutter compensationtechnology applied to5-axis NC machine is of both great theoretical andpractical value.The main focus of this thesis is the compensation of ball-end milling cutterthat is extensively applied to freeform surface processing. In this research, threeaspects of compensation are included, that is, cutter radius, cutter position andcutter length compensation. Through the analysis of existent algorithms forcutter radius compensation, the different problems in the processing of5-axisball-end milling cutter are resolved accordingly. Among them, using thetransformation principle of spatial coordinates, projection method has achievedthree-dimensional cutter radius compensation (with a reference to thewell-established two-dimensional cutter radius compensation method) and isapplicable to the processing of the side blade of ball-end cutter; while normalvector migration method can, through migration compensation, that is, cutterlocation migrates one compensation value along cutter contact point, ensure thatcutter contact point on curved surface and the cutting effect remain unchanged,which can help to realize the three-dimensional cutter radius compensation and isthus applicable to the processing of the head of ball-end cutter. From thekinematics modeling of mixed5-axis coordinated NC machine tools,transformation formula of kinematics coordinates is deduced and then analyzed;using multi-step calculation method, the position coordinates of B axis, C axisrotation, X axis, Y axis and Z axis are calculated sequentially to realize the compensation of cutter position. Meanwhile, the cutter length is considered asparameter in the deduction and the formula deduced can be directly applied to thecompensation of cutter length. Using Visual C++programming software andaccording to the cutter radius and cutter position compensation algorithmsmentioned above, reprocessing program is compiled, program interface designedand executable file generated.Emulating the manufacturing process, the processing effect has gonethrough overcut and undercut examination through Vericut simulation software.Through the comparison of the examination effect of overcut and undercut pointin each group of experiment, the accuracy of algorithms is proved. The actualprocessing with a5-axis NC machine tool has further proved the accuracy andfeasibility of NC code which has been treated with cutter compensation program.