Identification of optimal process parameters in twin-spindle machining

为了提高生产能力，双轴加工中心在工业上得到了广泛的应用。这样的机器配置在经济上是有利的，因为生产率在大约相同的占地面积下增加，并且只能实现适度较高的投资成本。然而，在实际应用中，磨削过程的动态不稳定性限制了磨削率的提高。在亚琛RWTH机床实验室DFG资助的一个研究项目中，可以确定并证明两主轴之间的夹角位置对加工稳定性的显著影响。使加工过程稳定且具有最大切削深度的最佳夹角位置取决于机床结构和加工过程的工艺参数。最佳角度位置的确定可以通过加工过程的模拟或在机床上进行一系列实验切割测试来完成。对模拟模型进行参数化以及在整个实验测试系列中运行的工作是相当大的。由于确定稳定性图或最佳角度位置的成本较高，目前的切割工艺的稳定性极限通常不是在工业实践中确定的。如果在批量生产的设置过程中发生再生包租，机器操作员通常会试图通过改变工艺参数来稳定工艺。如果该程序在几次尝试中不能导致稳定的过程，则切割深度将降低，从而降低生产率。为了利用不同主轴角度位置的潜力，必须开发一种程序，该程序允许根据当前工艺自动确定刀具1和刀具2的最佳角度位置。该研究项目的目标是开发一种带有分析软件的方法和测量设置，允许操作员在不了解机床动力学或颤振理论的情况下确定有效的工艺参数。因此，必须开发软件来分析在相关频率范围内所发生的振动的幅度。在相应的频率范围内，可以观察到振动幅度最小的刀具之间具有对应的角位移的过程被认为是有效的。

To increase the production capacity, twin-spindle machining centers are widely used in industry. Such a machine configuration is economically advantageous as productivity increase at approximately the same floor space and only moderately higher investment costs can be achieved. However, in practice, the removal rate is limited by the dynamic instability of the milling process. In a previous research project funded by the DFG at the Laboratory for Machine Tools (WZL) at RWTH Aachen University a significant influence of the angular position of the two spindles to each other on the process stability could be identified and demonstrated.The optimum angle position which enables a stable process with a maximum cutting depth is dependent on the machine structure and process parameters of the milling process. The determination of an optimal angle position can be done either through simulation of the machining process or series of experimental cutting tests on the machine. The effort to parameterize a simulation model as well as to run through the experimental test series is considerable. Due to the high cost for determination of stability charts or optimal angular positions, the stability limits for the present cutting processes are usually not be determined in industrial practice. If regenerative chartering occurs during the setup of series production, the machine operator usually tries to stabilize the process by varying the process parameters. If this procedure does not induce a stable process in a few tries, the cutting depth and thus the productivity will be reduced.To use the potential of the different spindle angular positions a procedure has to be developed that allows an automatic determining of the optimal angular position of tool 1 and tool 2 depending on the current process. The goal of this research project is to develop a methodology and a measurement setup with an analysis software, which allows an operator without knowledge of dynamics of machine tools or chatter theory to determine efficient process parameters. Therefore software has to be developed for analysing the occurring vibrations regarding their amplitudes in the relevant frequency range. The process with the corresponding angular displacement between the cutting tools, in which the lowest vibration amplitude can be observed in relevant frequency ranges, is identified as efficient.