The next step towards virtual machine tools: Simulation of damping effects caused by the machine-process interaction

机床和过程之间的相互作用可能导致不必要的振动甚至不稳定性，如颤振。其后果是增加刀具磨损，加工不足导致机床损坏。为了避免这些不必要的振动现象并提高机床的切削性能，有必要高精度地模拟机床与过程之间的相互作用。在德国研究基金会（DFG）资助的“机床中的阻尼效应”研究组中，分析了机电一体化机床结构中的阻尼，并针对不同的耗散源确定了可预测的线性和非线性阻尼模型。通过采用适当的建模方法，仿真中考虑了影响机电一体化机床结构阻尼的各种因素。这种建模方法与识别的阻尼模型一起允许以高精度预测机床结构的动态行为。为了在仿真中考虑切削过程以及机床结构，需要建立适当的切削力模型。研究小组解决了机床结构模拟的主要问题：阻尼建模。然而，对于过程阻尼效应，通常没有实用的模型和参数可用。过程阻尼由刀具和工件之间的相互作用产生，特别是在低切削速度下影响过程稳定性。这在钛和镍合金等难切削材料的加工中起着重要作用。忽略过程阻尼会导致对稳定极限的不准确预测。此外，机床结构中的阻尼也会受到加工过程的影响：改变加工位置、进给速度、主轴转速以及机床部件中的负载都会对结构的阻尼系数产生影响，但在仿真中没有考虑。为了在仿真中以足够的精度表示机床的整个系统和过程，需要考虑过程对整体阻尼的影响。这代表了虚拟机床的下一步，继研究单位。通过继续使用和扩展物理机床，可以弥补机床和过程中建模阻尼的差距，并显著提高仿真精度。这为优化机床、扩展过程稳定性极限、有针对性地设计加工过程以及随后通过使用稳定性最大值来提高切削性能带来了新的可能性。

The interaction between the machine tool and the process can lead to unwanted vibrations and even instabilities such as chatter. The consequences are increased tool wear, insufficient machining results up to damages to the machine tool. In order to avoid these unwanted vibrational phenomena and to increase the cutting performance of machine tools, it is necessary to simulate the interaction between the machine and the process with high accuracy. In the research group "Damping effects in machine tools" funded by the German Research Foundation (DFG), the damping in the mechatronic machine tool structure was analyzed and predictable linear and nonlinear damping models were identified for the different dissipation sources. By using an appropriate modeling approach, the various influencing factors on the damping of the mechatronic machine tool structure were taken into account in the simulation. This modeling approach together with the identified damping models allows to predict the dynamic behavior of a machine tool structure with high accuracy. In order to consider the cutting process in addition to the machine tool structure within the simulation, appropriate cutting force models are needed. The Research group addressed the main problem with the simulation of the machine tool structure: Modeling of the damping. However for the process damping effect there are usually no practicable models and parameters available. Process damping results from the interaction between the tool and the workpiece and affects in particular the process stability at low cutting speeds. This plays an important role in the machining of difficult-to-cut-materials like titanium and nickel alloys. Neglecting process damping leads to an inaccurate prediction of the stability limit. In addition, the damping in the machine tool structure is influenced by the process: Varying the machining positions, feed rates, spindle speeds as well as loads in the machine components has an impact on the structure’s damping coefficients, but is not taken into account in the simulation. In order to represent the overall system of the machine tool and the process in the simulation with sufficient accuracy it is necessary to consider the influences of the process on the overall damping. This represents the next step to the virtual machine tool, subsequent to the research unit. By continuing to use and expanding the physical machine tool, the gap in modeling the damping in the machine tool and the process can be closed and the simulation accuracy can be increased significantly. This results in new possibilities for optimizing the machine tool, expanding the stability limits of processes, designing the machining process in a targeted manner and subsequently increasing the cutting performance by using stability maxima.