Novel multi-feature bar design for machine tools geometric errors identification

Abstract

This paper describes the development of a new thermo-invariant material standard (new multi-feature bar (MFB) standard) and an associated procedure for the identification of 21 geometric errors on 3-axis machine tools (MT). The design of the new standard allows to extract three intrinsic parameters for each position of the MFB: 1 linear positioning error and two straightness errors.To ensure the metrology traceability chain to the SI metre definition, the calibration of the MFB is carried out using an accurate traceable coordinate measuring machine (CMM) when applying the reversal technique. The established procedure for the identification of the geometric errors was applied on a 5-axis MT, leading to the identification of the apparent 21 geometric errors of the 3 linear axes. To achieve with this purpose, the number of required positions of the MFB was optimized and reduced to only 6 positions, while using both rotary axes. The collection of raw data for each measurement was performed thanks to an accurate touch probe, linear encoders of the MT, as well as a developed interface that is independent of the industrial computer numerical control (CNC). Furthermore, the sensitivity of the geometric errors on the linear axes position is highlighted.