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Innovativer linear-rotatorischer Mehrkoordinatendirektantrieb für Werkzeugmaschinen im Einsatz

Innovative linear-rotary multi-coordinate direct drive for machine tools in use

The linear-rotary multi-coordinate direct drive with machining spindle for milling operations

A novel drive design of a multi-coordinate direct drive has been developed by researchers at the Institute of Production Engineering and Machine Tools (IFW). A planar multi-coordinate direct drive has already been developed in the past. This concept has now been transferred to a new type of linear and rotational multi-coordinate direct drive, which can thus move with high precision and also highly dynamically with just one rotor. This innovative drive offers high potential for positioning the machining spindle in turn-mill centers.

In state-of-the-art machine tools, several feed drives are often interconnected in a serial kinematic system to position a tool or a workpiece. In principle, a subordinate axis carries the superimposed axes. However, the additional mass of the superimposed axes limits the overall dynamics. Other disadvantages of this design are limited stiffness and accuracy, since several connecting elements are required between the axes. To do away with serial kinematics and the associated disadvantages, researchers at IFW have developed a new type of multi-coordinate direct drive in cooperation with Gildemeister Drehmaschinen GmbH and Franz Kessler GmbH. The novelty of the drive is that it can be traversed without serial kinematics in linear and rotational axis direction with only one machine component (rotor). In order to ensure the load-bearing capacity of the rotor bearing even during highly productive machining, a hydrostatic bearing and clamping unit was specially developed for this purpose ( ).

After the drive was optimized simulatively using the finite element method with respect to high power density and low power loss at IFW, the multi-coordinate direct drive was built to explore its performance and limitations. A travel range of ± 100 mm along the Y linear axis and ± 120 ° along the B rotational axis was achieved. These are similar to the travels of a conventional turning-milling center. Based on tests, it was shown that a maximum torque of 1,471.6 Nm and a feed force of 4,893.7 N are possible with the drive. This high performance is also possible with simultaneous actuation of both axes with only minor losses (max. 10.6%). In the investigation of the axis dynamics, speeds along the linear axis of 78 m/min and the rotary axis of 158.3 rpm were thus achieved. "This high dynamic is remarkable and corresponds to an increase of +126 % compared to a machine tool with serial kinematics and identical traverse path," says research associate Patrick Ahlborn.

At the end of the project phase, the suitability of the multi-coordinate direct drive for machining processes was investigated. Several test geometries, such as full and half cuts, were successfully milled in several milling tests. A displacement of the axis position by the machining forces was not detected even at engagement depths of 5 mm. Milling of the test geometries was possible with stable axis control and axis position. The drive can be seen in action as a video at the following link (


For further information, please contact Patrick Ahlborn, Institute of Production Engineering and Machine Tools at Leibniz Universität Hannover, by phone +49 (0) 511 - 18163 or by e-mail (