Fine positioning system for large components

Prior to the profile grinding process of large gear wheels with a weight of several tons, a very precise alignment of the workpiece is required in order to meet the narrow tolerances. However, three-axis grinding machines are not able to correct alignment errors in four axes and the manual alignment process is a time intensive procedure. Automation of the manual process offers the potential to increase efficiency of the process  normously. For the positioning of large and heavy components of up to 4.8 t, a fine positioning system was developed. The system is suitable for micrometer precision positioning in four degrees of freedom. Two linear axes are carried out as a conventional cross guide. Two rotational degrees of freedom are applied by a circular membrane, which is used as a flexure joint for the wobble unit. The presented prototype is able to correct eccentric errors of ±2.5 mm and wobble errors of ±0.1° prior to the process. Finally, the system was validated in a profile grinding process of a 4 t wind turbine gear. The results show high stiffness values and qualify the device for the use in profile grinding machines. The total tooth pitch deviation was measured with 10 μm (gear diameter: 1146 mm), which demonstrates the uniformity of the rotational stiffness.