Error Analysis And Control For Toolpath Planning In Five-axis Numerical Control Machining

Complex geometric parts with free form surfaces are widely used in aerospace, automotive and die-mold industries. Five-axis NC machining has dominant advantages in machining efficiency and quality for those parts. Therefore, it is serious to analysis the machine error for ensuring the accuracy of five-axis NC machining.The error analysis and control for toolpath planning in five-axis numerical control machining is studied in this paper. Mostly, the machine error in five-axis NC machining can be simplified as two-dimensional model, such as geometric error and kinematic error discussed in this paper. Additionally, the three-dimensional model needs to be obtained to satisfy advanced requirements in some cases. Hence, the tool envelope surface is computed by a vector calculation method for that purpose. Some details investigated in this paper are stated as follows.(1) The geometric error and the machine error related to the motion of machine tools are discussed with two-dimensional model. The geometric error, especially for scallop height, is investigated in the tool path planning stage. Additionally, the machine error related to the motion of machine tools, especially for non-linear error, is discussed in practical machining. With the kinematic chain of the machine tool, the control scheme for the motion of the cutter is studied. Furthermore, the difference of the tool axis rotation scheme applied on the practical machining and tool path planning is introduced. And this difference will cause the tool axis error which result in non-linear error produced approximately in the plane which perpendicular to the cutter feed direction. Additionally, the control method is proposed to improve the machining precision.(2) A vector calculation for tool envelope surface in five-axis machining is presented to obtain the three-dimensional model of the machine error. By introduing the envelope theory and some geometric characteristic of the cutter, the vector method is proposed. Furthermore, this method is extended to calculate the envelope surface directly from CL-data. Additionally, the tool envelope surface formed by general motion is calculated, and the critical curve position on the cutter surface is also analysised with the motion parameters of the cutter.