De-coupling of an Optical Grating Based Measurement Normal from the Machine Tool Structure

Precision machine tools use optical encoders for accurate position feedback [1,2]. A novel encoder based on three cross grid gratings mounted on a thin wall beam and a sensor head consisting of six optical sensing elements was developed to calibrate the linear machine tool axis in six Degrees of Freedom (Figure 1). The feasibility of this device has been tested and verified under laboratory conditions [3]. However, in order to use the device under varying environmental conditions.it has to be guarenteed that the measurement normal is decoupled from the mounting surface in order to prevent induced forces to distort its shape. Therefore this paper descripes the design procedure for such de-coupling mounts based on slip stick free flexures.