Planar Precision

Precision in an X-Y plane can be significantly improved by using orthogonal plane mirrors as feedback references. In these cases, the work is moved in X-Y while the process tooling (vision camera, laser scriber, gripper end-effector, etc.) is rigidly fixed above. As can be seen in the sketches below, the relative tooling-to-workpiece relationship (at the intersection of the X & Y beams) will be as precise as the X-axis and Y-axes mirror's flat surface. Mirrors also assure precise straightness of motion. For example, as the X-axis moves along its bearing path, the Y-axis mirror feedback constantly senses variations in Y-axis position and corrects for any X-axis straightness conditions. Likewise, X mirrors sense Y-axis straightness deviations. It should be noted that in the stacked configuration depicted below, plane mirror interferometer systems only assure X-Y precision and not deviations in Z. Flatness of travel, pitch, roll, and excessive yaw errors are not sensed nor automatically corrected by planemirror interferometer systems.

Errors normal to the X-Y plane (vertical direction) can be minimized by eliminating the affects exhibited by varying cantilevered loads in staked stages. As shown in the sketch below, the moving load has consistent bearing support to lapped granite reference surface throughout it full range of motion in the X-Y plane. Balanced brushless linear servomotors are typically used with these non-contact friction-free air bearing platforms to provide the ultimate in servo stiffness, smooth motion, and precise position control.