Balancing of spindles for ultra-precision high performance milling operations

在项目的第一阶段，通过开发平衡机原型以及通过耦合系统增强不平衡检测，证明了自动平衡系统的总体可行性。平衡样机能够将转子的不平衡状态改善到G0.004，这是传统的手动UP平衡程序无法达到的。在第二个项目阶段，应开发一个完全自动化的平衡系统的基础。平衡过程的稳定性、速度和精度与机床结构以及该研究小组的其他项目密切相关，特别是与热工具对准和新型进给轴。只要平衡过程与主轴加速同时进行，完全自动化将使平衡过程的二次处理时间减少到零。因此，即使在较低的主轴速度下，也必须可靠地检测现有的不平衡。结果表明，由于空气轴承的刚度有限，在较低的速度下的不平衡检测只能在主轴转子内部进行。改变主轴和机床底座之间的结构耦合特性的原理已被证明是非常有效的。因此，在今后的工作中，它将被视为平衡系统的一个组成部分。通过扩展耦合系统以调整结构阻尼，可以设计动态耦合系统。由于平衡系统的复杂性，控制和监控系统的建模是必要的，包括与动态结构特性、热工具对准和进给轴的相互作用。为了更深入地了解影响光学表面生成的相互作用，必须对这些进行分析。除了转子不平衡之外，其他因素（如路径偏差或振动）也会影响生成的光学表面的质量。例如，进给轴系统或飞切半径的变化会引起路径偏差。机械加工的光学表面代表了所有这些因素的总和。各因素对生成光学面形的影响用一般的分析方法是无法检测的。为了分析这些依赖关系，必须根据表面产生的空间频率定义特征值，重点关注主轴不平衡的影响。在第二个项目阶段结束时，自动平衡系统，以及项目中开发的其他组件，将被集成到一个演示平台，并评估其在平衡和超精密铣削操作中的综合性能。

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.