Thermal non-linear behaviour in optical linear encoders

Thermal errors in machine tools are some of the major inaccuracy sources. For their correction, two approaches can be followed: consider the machine as a whole or its constituent members. Errors caused by linear encoders are examined. The mutual effects between aluminium extrusion and glass scale result in thermal coefficient changes. Besides, non-linearities with respect to length modification are found as a consequence of the different stress conditions in different sections of the encoder. This behaviour makes the simple linear thermal correction of optical linear encoder measurements inaccurate. The research presented here tries to identify and to estimate non-linearities caused by the linear encoder as a method to improve thermal error correction procedures.