Project Details
Projekt
Balancing of spindles for ultra-precision high performance milling operations
Subject Area
Metal-Cutting and Abrasive Manufacturing Engineering
Term
from 2014 to 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 211652309
In the first project phase, the general feasibility of an automatic balancing system was proven by developing balancer prototypes as well as enhancing the unbalance detection by a coupling system. The balancing prototypes are able to improve the unbalance state of a rotor up to G0.004, which is unreachable by conventional manual UP-balance procedures. In the second project phase, the basis for a completely automated balancing system shall be developed. The stability, speed and accuracy of the balancing process are closely linked with the machine structure as well as the other projects of this research group, particularly with the thermal tool alignment and the novel feed axis.A complete automatization will allow the reduction of the secondary process times of the balancing process down to zero, as long as the balancing process takes place simultaneously to the acceleration of the spindle. Therefore, the detection of the existing unbalance has to be reliable even at lower spindle speeds. It was shown that the unbalance detection at lower speeds is only possible inside the spindle rotor due to the limited stiffness of the air bearing. The principle of changing the properties of the structural coupling between spindle and machine base, has proven to be very effective. Therefore, it will be considered as an integral part of the balancing system in future works. By extending the coupling system to also adjust the structural damping, a dynamic coupling system can be designed. Due to the complexity of the balancing system, a modelling of the control and monitoring systems is necessary with respect to the interactions with the dynamic structural characteristics, the thermal tool alignment and the feed axes.In order to create a deeper understanding of the interactions that influence the generation of the optical surface, these have to be analyzed. Besides the rotor unbalance, other factors like path deviations or vibrations, are affecting the quality of the generated optical surface. Path deviations, for example, arise from the feed axes system or changes of the fly-cut-radius. The machined optical surface represents the sum of all these factors. The influence of each factor on the generated optical surface is not detectable with common analysis methods. In order to analyze these dependencies, characteristic values have to be defined from the spatial frequency generated from the surfaces, with focus on the influence of the spindle unbalance.At the end of the second project phase, the automatic balancing system, among the other components that are developed within the project, will be integrated into a demonstration platform and evaluated for their combined performance in balancing and ultra-precision milling operations.
DFG Programme
Research Units
Co-Investigator
Dr.-Ing. Oltmann Riemer
