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2008
Conference Paper
Titel
Integral design for a high precision rotary-axis system
Abstract
Where the complex form shapes of work pieces require five-axes machining in highest precision, the machine systems that are available on the market, are often limited in their accuracy (spatial positioning accuracy < 10 mym). In previous enquiries, the five-axes machining accuracy was identified as limiting factor for the high precision manufacturing of complex micro parts for high end applications. Especially the rotary axes of conventional five-axes machine design affect the machine accuracy significantly. For this reason the Fraunhofer IPT initiated a research project focusing on the reduction of the rotational axis error by implementing an integral design strategy consequently. A concept has been developed integrating hydrostatic bearings into a torque motor. Therefore electrotechnical as well as mechanical issues have been worked out following the integral resolution method for increasing the five-axes accuracy. Focusing on the reduction of the error activating cantilevers caused by the rotary axes, a concept has been worked out integrating hydrostatic bearings into a torque motor. Thereby, a radial bearing is integrated into the air gap of the torque motor while two axial bearings are positioned in-between the work piece table and the face side of the motor. Following the integral design idea principally, the bearing pockets are integrated into the primary part of the drive and the counter bearing surfaces are provided by the work piece table, the motor's face side and the circumference of the rotor. The integration of the radial hydrostatic bearing changes the electro-magnetical, the mechanical as well as the thermal conditions of the torque motor although the bearing behaviour will be affected by the mechanical stiffness (gap variation) and by the temperature (gap variation and oil viscosity) of the torque motor.
Language
English