Process stability of parallel turning processes

为了提高加工过程的生产率，越来越多地使用具有多个刀架的车床。这些车床的特点是可以在单个旋转工件上同时使用多个刀具。无论是在工件的不同区域进行刀具啮合，还是在同一切削表面上同时进行切削，在这两种情况下，都可能出现颤振形式的过程不稳定性。颤振是机床结构动力学行为与切削过程相互作用而产生的一种自激、自增强的再生现象，目前对并联车削加工过程稳定性的研究较少。在WZL以前的研究中，已经可以检测到双主轴铣削过程中传递柔量对过程稳定性的主要影响。传递柔量描述了由于第一工具上的力而导致的第二工具上的位移。在同一切削平面上使用多个刀片的平行车削过程由于共享切削表面波纹度而引起相互激励，本研究项目的目标是确定、建模和解释平行车削过程的稳定性行为。预计切削刀具之间的径向角位置对过程稳定性的影响是显著的，因为该角度直接影响与稳定性相关的刀具死区时间。随后，该角度将连续变化以产生时变死区时间（类似于主动主轴速度变化技术）。这是通过扩展常用的过程-机器交互模型来实现的。使用时域模拟，可以研究时变工艺参数。已经设计了一个测试台来研究基本参数并验证模拟结果。该测试台由两个单质量振荡器组成，其角位置可调。使用该测试台，机器的行为可以减少到一个单一的质量振荡器。因此，研究将主要集中在模拟预测的过程-机器的相互作用。使用虚拟模型，适当的优化策略，提高稳定的切屑去除率将推导和验证。最后，通过上述程序获得的见解被用来创建一个仿真模型的工业车床与多个刀具转塔，这将是实验验证。

To increase the productivity of machining processes, lathes with multiple tool turrets are used increasingly. These turning machines are characterized by the possibility of simultaneous engagement of multiple tools on a single rotating work piece. Either the tool engagements takes place at different areas of a work piece or the cutting is carried out simultaneously on the same cutting surface.In both cases, process instabilities in the form of chattering may occur. Chattering is a self-excited and self-reinforcing regenerative phenomenon, resulting from interactions between the dynamic behavior of the machine tool structure and the cutting process.So far, there is a lack of research in the field of process stability of parallel turning processes. In previous studies from WZL a major influence of the transfer compliance on the process stability during double spindle milling could already be detected. The transfer compliance describes the displacement on a second tool as a result of a force on the first tool. Parallel turning processes using multiple blades in the same cutting plane induce mutual excitations due to the shared cutting surface waviness.The goal of this research project is the determination, modeling and interpretation of the stability behavior of parallel turning processes. The influence of the radial angular position between the cutting tools on the process stability is expected to be significant, because this angle directly affects the stability-relevant tool dead time. Subsequently, this angle will be varied continuously to generate a time variant dead time (analogously to active spindle speed variation techniques). This is done by extending the commonly used process-machine interaction models. Using a time-domain simulation, time variant process parameters may be investigated. A test bench was already designed to investigate the underlying parameters and to validate the simulation results. This test bench comprises of two single mass oscillators, which are adjustable in their angular positions. Using the test bench, the machine behavior can be reduced to that of a single mass oscillator. Thus, the research will be focused primarily on simulative prediction of process machine interaction. Using the virtual model, suitable optimization strategies for increasing the stable chip removal rates will be derived and validated. Finally, the insights gained by the aforementioned procedures are used to create a simulation model of an industrial turning machine with multiple tool turrets, which will be experimentally validated.