A Contribution to the Analysis and Compensation of the Geometric Error of a Machining Center

This paper deals with the modeling and compensation of the geometric errors or a three-axes machining center. Rigid body kinematics is used to develop a model relating the observed error vector at a point in the machine's workspace to Its coordinates. The machine constants (e.g. lengths or the members or the machine's kinematic scheme) and the errors in the form and dimensions or each of these members become the model coefficients. The model is then analyzed to show that, if the positioning error or each or the axes is zero, the coefficients of the models (the Individual errors or the members or the machine's kinematic scheme) can be evaluated by observing the error vector at a few points, forming a particular pattern. In the machine's workspace. Closed-form equations ire derived for the coefficients under these conditions and a heuristic self-organizing modeling procedure, the GMDH algorithm. Is used for modeling the positioning error under varying thermal conditions. This makes It Is possible to estimate the geometric error, usually an expensive task in time, effort and skill, from a few observations or error in the machine's workspace. Also, with periodic updates or the model, it is possible to compensate for thermal Influences.