Research On Configuration And Optimization Of Tool Orientation In Five-axis CNC Machining For S-shaped Specimen

S-shaped specimen is a new accuracy test specimen for CNC machine tool,and it's widely used in the accuracy test and acceptance of machine tools by most machine tool manufacturing enterprises.The processing of the specimen is a typical complex surface machining.In this paper,configuration and optimization of tool orientation in five-axis CNC machining for S-shaped specimen are studied.Based on the kinematics of five-axis machine tools and the geometric,material characteristics of S-shaped specimen,the process planning of the specimen is made,and the problems of nonlinear error and singularity in five-axis machining are raised.The tool orientation of interpolated cutter location point is calculated according to the linearized tool trajectory so that the nonlinear error is reduced.Based on the principle of local minimum deformation,the tool-path curve and cutter location points are projected to the boundary of the singularity region,which avoids the risk of machining in the singularity region.The main contents of this paper are as follows:In Chapter 1,the reviews of tool orientation calculation and optimization in five-axis machining for S-shaped specimen are given.The background and significance of the research are expounded,and the contents and framework of this paper are introduced.In Chapter 2,the kinematics of table-spindle hybrid five-axis machine tool is given according to the structure and kinematics chain of the machine tool.The geometric characteristic of the specimen is analyzed according to the parameters and constructing method of the specimen,and then the process planning of the specimen is made,considering its geometric and material characteristics.And the problems of nonlinear error and singularity in five-axis machining for different regions of the specimen are raised.In Chapter 3,a configuration method for interpolated tool orientation in S-shaped specimen machining is put forward.The tool orientation of interpolated cutter location changes linearly in the plane formed by the first and last tool orientations of the interpolation block,and the tool trajectory is get in this way.And then calculate the interpolated tool locations and tool orientations in the workpiece coordinate.This method avoids the deviation of interpolated cutter locations' tool orientations,and reduce the nonlinear error in five-axis machining.In Chapter 4,an optimizing method of avoiding singularity in five-axis machining is proposed,based on local minimum deformation.Based on the analysis of the mechanism of five-axis machining singularity,the projection of singular cone is used to judge whether there is a risk of singularity in the cutter location points and the tool-path curve.The cutter location points and the tool-path curve with potential singular risk are projected onto the boundary of the singular region.The optimized tool-path curve is fitted to avoid the singular region.In Chapter 5,the theoretic methods and techniques are applied to the tool orientation configuration and optimization in the specimen machining with the machine tool design scheme,which proves the feasibility of the methods in this paper.In Chapter 6,the further research is put forward after summarizing the achievements of this dissertation.