数控机床整机动态特性评价方法

Evaluation method of dynamic characteristics of whole NC machine tool

动态特性是衡量机床性能的一项重要指标,但目前并没有较好的数控机床整机动态特性评价方法。利用真实的动态切削力对数控机床进行激励,能够快速获取机床在切削力作用下的动态特性。鉴于切削参数会影响各频率成分对应的切削力幅值,基于不同工件材料和切削参数下的动态切削力,建立动态激振力模型,通过分频段激励来检验数控机床在不同频段下的动态特性。通过有限元仿真分析,判断数控机床在各个频段下的动态特性;对振动信号进行快速傅里叶变换,得到机床振动时的主要频率成分,为优化机床动态特性提供指导;对比各种动态切削力激振下不同机床的动刚度,评价不同机床动态特性的优劣。最后,通过激振试验验证了仿真结果的准确性。结果表明上述方法简单实用,能快速评价数控机床的动态特性,具有一定的实用价值。

The dynamic characteristics is an important index to measure the performance of machine tools.However, there is no better method to evaluate the dynamic characteristics of whole NC(numerical control) machine tool. Through the excitation of real dynamic cutting force to the NC machine tool, the dynamic characteristics of the machine tool under the action of cutting force can be quickly obtained. In view of the fact that the cutting parameters would affect the amplitude of cutting force corresponding to each frequency component, a dynamic excitation force model was established based on the dynamic cutting forces under different sample materials and cutting parameters. The dynamic characteristics of the NC machine tool in different frequency bands could be tested by frequency band excitation. Through the finite element simulation analysis, the dynamic characteristics of NC machine tool in each frequency band was judged. The main frequency components in the vibration of machine tool were obtained by fast Fourier transform of vibration signal, which could provide guidance for optimizing the dynamic characteristics of machine tool. The dynamic stiffness of different machine tools under excitation of various dynamic cutting forces was compared to distinguish which machine tool had better dynamic characteristics. Finally, the simulation results were verified by the excitation test. The results indicate that the above method is simple and practical, and can quickly evaluate the dynamic characteristics of NC machine tool, which has certain practical value.