刀具-刀架耦合系统的动态可靠性及频率可靠性灵敏度研究

Cutter tool system and carrier system are key functional components of CNC machine tool, some factors such as indexing precision of cutter carrier, vibration of cutter head and cutter carrier tank, and Y axis displacement of cutter carrier have effects on reliability of cutter tool system. Conversely, forced vibration caused by coupling exciting force of cutting vibration has influence on reliability of cutter carrier system. In the sensitive frequency domain, cutter tool and carrier coupling systems is tend to bring about resonance or cutting noise, which not only have effect on quality of processing of production lifetime of cutter tool and carrier, even quality and performance of the whole CNC machine tool. Mathematical models on dynamic reliability and frequency sensitivity of cutter tool and carrier coupling systems will be established, and all kinds of failure mechanism of cutter carrier system and their influence on reliability of cutter tool system can be studied as well, meanwhile, a analysis method on frequency reliability sensitivity avoiding system operating in the sensitive frequency domain will be proposed based on dynamic characteristics of cutter tool and carrier coupling systems in this project. Through establishing a physical experimental platform of dynamic reliability with high performance, design on dynamic reliability and reliability sensitivity, and technique research on performance tests of productions will be developed, thus an evaluation method on reliability can be obtained from design, test to operation, and reliability of cutter tool and carrier coupling systems is improved as well, which will improve keeping high accuracy and average zero-failure working time of top grade CNC machine tool.

刀具系统和刀架系统是数控机床的关键功能部件，刀架分度精度、刀盘振动、刀架箱体振动以及刀架Y轴位移等因素都会对刀具系统可靠性产生影响。由刀具切削振动耦合激励而产生的强迫振动反过来也影响着刀架系统的可靠性，在敏感频域内，刀具-刀架耦合系统容易产生共振或切削噪声。这不仅影响产品的加工质量和刀具、刀架的寿命，甚至影响整台机床的质量和性能。本项目拟建立刀具-刀架耦合系统的动态可靠性及频率可靠性灵敏度数学模型，研究刀架系统各种失效机理以及对刀具系统可靠性的影响，研究刀具-刀架耦合系统的动态特性，提出避免系统在敏感频域或模态下运行的频率可靠性灵敏度分析方法。同时搭建高性能的动态可靠性物理实验平台，开展产品动态可靠性设计、可靠性灵敏度设计与性能试验技术研究，获得刀具-刀架耦合系统从设计、试验（测试）到运行的可靠性评价方法，提高刀具-刀架耦合系统的可靠度，从而提高高档数控机床的精度保持和平均无故障工作时间。

刀具及伺服刀架作为数控机床关键组成部分，是数控机床能够完成多种加工模式和高精度加工的主要保障。伺服刀架在高速运转进行对工件的切削时，齿盘分度装置受到的齿面应力与刀架整机受到激振力作用可能引发的共振问题，对刀架的可靠性以及加工精度都产生显著影响。本课题对一种典型的刀架结构径向出刀双伺服刀架进行可靠性与灵敏度的研究，并主要开展以下工作：.(1) 研究刀具的动态可靠性灵敏度，并建立了刀具灵敏度的数学模型。刀具各设计参数的选取直接影响刀具的可靠度。推导了刀具各设计参数的动态可靠性灵敏度计算公式，并给出了各设计参数的动态可靠性灵敏度的变化曲线。研究表明，刀具各设计参数的改变对其可靠性的敏感程度大小不一，对敏感参数的选取要加以控制，以提高刀具的可靠度和被加工零件的精度。同时为提高刀具-刀架系统的可靠性提供理论依。.(2)端齿盘加工精度的高低会直接影响到整个刀架的分度精度。在对端齿盘加工误差进行分析的基础上建立了端齿盘的分度误差模型，利用二阶矩和摄动方法求出端齿盘的可靠性指标，并计算出其可靠度以端齿盘的分度误差模型为基础，将可靠性理论与灵敏度分析方法相结合，给出了动力伺服刀架端齿盘分度精度可靠性灵敏度设计的分析方法。通过算例得出了端齿盘各随机参数的可靠性灵敏度变化规律，并分析了各随机参数的变化对端齿盘分度精度可靠性的影响。研究表明，端齿盘各设计参数的改变对其可靠性的敏感程度不一，可通过优化敏感参数来提高齿盘的分度精度可靠性同时为提高刀架系统的分度精度可靠性提供理论依据。.(3)考虑径向出刀双伺服刀架在切削过程中激振频率对刀架系统可靠性的影响，故对刀架整机进行频率靠性及灵敏度分析。由于刀架整机模型中的参数数目过多，部分参数的变化对整机固有频率的影响程度较小，所以对刀架整机模型中的参数进行筛选，同时分析了筛选后的10个参数发生变化时对整机固有频率的影响。接下来利用神经网络拟合模型中筛选后的10个参数与刀架整机第一阶固有频率的关系，并由此建立刀架整机的频率可靠性极限状态方程，完成对径向出刀双伺服刀架系统频率可靠度及灵敏度的求解。