Laser-based measurement of thermo-elastic structural deviation of machine tools

Thermo-elastic deformations are one of the most significant sources of machine tool inaccuracies. The structure components of the machine tools can elongate and also bend due to inhomogeneous distribution of temperature in the machine structures. There are numerous methods to measure and monitor structural deformations. However, the measurement of the structural bending is still very challenging procedure. In this paper, a simple laser-based sensor is introduced for the measurement of the structural bending of machine tool components. The sensor is made of a laser unit, a precision optics based on charge-coupled device (CCD) and electronics for image processing. These measuring hardware are mounted in a metal tube: the laser at one end of the tube and the CCD at the other end of the tube. With the change of the laser beam position on the CCD, the bending of the tube can be measured perpendicular to the laser line of sight in two dimensions. To measure the accurate laser position, an image processing algorithm is applied and embedded in the integrated electronics. For the validation of the sensor capability, the sensor is mounted on two different machine tools. The measurement of the sensor is applied under thermal loads of axis movements after ISO 230-3. The sensor potential is analyzed with the correlation between the sensor measurement and different independent validation measurements.