Computer Aided Calibration of the Geometric Errors of Multi-Axis Coordinate Measuring Machines

Abstract

The concept of a rapid calibration method for obtaining the individual components of the geometric error of CMM (coordinate measuring machines) is applied to the case of the two-dimensional (in-plane) error. Analysis of the geometrical model of the structure which can be easily obtained from first principles for any specific kinematic design of multi-axis coordinate measuring machines reveals which individual components have to be measured and how they combine. The analysis is extended to include weight deformation effects. Computer controlled calibration with the use of laser interferometer allows continuous sampling ‘on the fly’ of the target points for the efficient, automatic measurement of the positioning, straightness and squareness and angular motion errors. The systematic, random and hysteretic elements in each error component are evaluated. Interactive software programs offer versatility and choice of variables and appropriate fixturing is used to reduce the set-up time, so that a realistic overall time scale is achievable.