Workshop-suited geometric errors identification of three-axis machine tools using on-machine measurement for long term precision assurance

Abstract

In this paper we present a novel methodology for fast geometric errors identification of three-axis machine tools (MTs) using on-machine measurement. For this purpose, a new design of a three-dimensional artifact is proposed. The artifact allows to identify the linear positioning error and the two straightness errors of any linear axis of MTs with cartesian kinematics and the perpendicularity error between the axes. The prerequisite for the measurement is that the roll, pitch and yaw errors of all axes have already been measured and are negligibly small. The presented methodology is especially suitable for regular control of the machine accuracy in order to ensure the precision of the machining in the long term.As part of this work, an artifact was made of thermo-invariant material (Invar) and calibrated with an accurate coordinate measuring machine (CMM). This artifact was used to identify the geometric errors of an MT with three linear axes, with the raw data being collected using a 3D touch trigger probe. The measured errors were compared with results from laser interferometer and ballbar measurements. Moreover, the measurement uncertainty of presented methodology was analysed and compared with those of the laser interferometer and ballbar.