Limitations of laser diagonal measurements

The introduction of B5.54 and ISO230-6 machine tool performance measurement standards is increasing the popularity of laser interferometer diagonal, step diagonal and vector methods for the evaluation and compensation of machine tool errors. This is due to the potential reduction in calibration time, these methods can provide over the more conventional laser interferometer-based linear, angle and straightness measurements taken along lines parallel to the machine’s X, Y and Z axes. aper highlights limitations in the results produced by diagonal-based measurements and by the more recently introduced vector or step diagonal methods. The purpose of this paper is to alert potential users of these methods to their limitations so they can make informed decisions as to whether the reduction in calibration time they can provide outweighs the loss of accuracy and detail in the results. It also indicates some of the dangers in using laser diagonal data alone for the compensation of machine tool errors.