LASER INTERFEROMETRY FOR STRAIGHTNESS MEASUREMENTS IN A WEAKLY CONTROLLED ENVIRONMENT

摘要

Straightness measurements for the geometrical inspection of machining tools have been operated in a weakly controlled environment (concerning temperature, pressure, humidity and induced mechanical vibrations) with reference to industrial manufacturing departments. Measurements have been performed by means of a Wollaston prism laser interferometer. A first experimental characterization of this instrumentation has been operated by repeatability tests conducted in controlled and not controlled environments, considering different relative positions for the interferometer and the laser head. Then a calibration diagram has been constructed, assessing the accuracy and the instrumental uncertainty in the case of displacement measurements in a plane perpendicular to the laser beam direction. In a second stage a suitable method has been developed to estimate the uncertainty level associated to straightness measures operated by the laser interferometric technique and also by traditional instrumentation, such as taut-wire and microscope and precision level. Measurement uncertainty is estimated by means of the Monte Carlo Method and according to standards. Measures obtained by the laser interferometric method prove to be affected by higher levels of uncertainty than those coming from traditional approaches.