KDP晶体单点金刚石飞切轨迹波纹误差辨识研究

Research on the Identification in of Waveness Error in Diamond Fly Cutting for KDP Crystals

频率辨识是消除或抑制KDP晶体超精密金刚石飞切轨迹波纹误差的重要前提。针对该问题,提出了一种基于空间频率变换的飞切轨迹波纹误差辨识方法。该方法通过提取表面飞切轨迹上的轮廓幅值,计算其波纹误差的空间频率,然后采用飞切线速度进行转换,获得时间域上的频率值,实现波纹误差特征频率的准确分离。将误差特征频率与切削振动频率、机床气浮主轴系统的固有频率进行对比分析,明确了气浮主轴在断续切削力作用下产生的自激振动和来自电机的受迫振动是导致KDP晶体金刚石飞切波纹误差的根本原因。在此基础上,通过对主轴驱动及结构的优化,工艺实验结果表明,大口径KDP晶体飞切后的PSD1(2.5~33mm)频段内波纹误差RMS值由53nm降低至12nm。

Frequency identification is the prerequisite for eliminating or reducing ripple wave error in ultraprecision diamond fly cutting on KDP crystals.To address this problem,a method for the identification of the ripple waves error of diamond fly cutting trajectory based on spatial frequency transformation was proposed.The method calculated the spatial frequencies of ripple wave error according to the fly cutting profile of the arc-shaped trajectories.Then,the accurate separation of the characteristic frequencies was realized when the frequencies were transformed in time.The contrast between the characteristic frequencies of wave error with the cutting vibration frequencies and the natural frequencies of air spindle showed that the self-excited vibration at the natural frequencies of air spindle under intermittent cutting forces and the forced vibration from the motor was the primary reasons for ripple wave erro.Base on the above conclusion,by optimizing the structure and drive of the air spindle,the RMS value at PSD1 band(2.5~33mm)of KDP crystal fly cutting surface reduced from 53 nm to 12 nm.