Prediction of Quasistatic Errors in Three-Axis CNC Machining Centers

Quasistatic error sources, which include thermal, mechanical loading and geometric error sources, are responsible for a very large proportion (typically, 70%) of the volumetric errors of a CNC machine tool. This paper discusses the development of a general quasistatic error model for multi-axis CNC machining centers using rigid body kinematics. To predict the quasistatic errors at any position in the workspace, a new method was proposed using the meshing concepts developed in the FEM literature. Finally, the spatial rate of change of the error was analyzed. The model and analysis method can be used as the basis of a compensation scheme as well as in budgeting of errors on a machine tool.