A Displacement Method for Machine Geometry Calibration

It is shown that the volumetric errors of a three-axis machine tool or measuring machine can be determined by measuring the displacement error along 22 lines in the machine work zone. Pitch and yaw are derived from measuring the displacement error on two parallel lines for each axis. The squareness and straightness errors are determined by measuring two diagonals and one additional line. Roll errors are derived from the straightness errors on two parallel planes. Formulae for calculating these components of error and also the three-dimensional positioning error at any particular point are given. Experiments show that this method simplifies machine calibration, reduces the equipment needed, and can improve accuracy.