A KINEMATIC MODEL FOR MACHINE-TOOL ACCURACY CHARACTERIZATION

A method for characterising machine tool accuracy is presented in this paper, using a compact quasi-static error model of a three-axis horizontal machining centre. Rigid-body kinematics and homogeneous coordinate transformation were used in this model. A metrology pallet was designed so that coefficents in the error model can be updated periodically. Ten measurement points were allocated on two perpendicular planes of the metrology pallet. One of the measurement planes was on the work table and the other was perpendicular to the table. Two different length touch trigger probes were required for error measurements. Establishing or updating the error model can be carried out in-process without disturbing the workpiece setup. The proposed compact error model is an improvement over past work for a production environment because of its robustness and convenient calibration procedure. The error model was tested in two dimensions and a good error prediction capability was observed in warm machine states.