光学自由曲面快速刀具伺服车削误差的补偿

Error compensation of optical freeform surfaces in fast tool servo diamond turning

受各种误差因素以及周期性变化的切削力的影响,快速刀具伺服金刚石车削技术往往难以用一次车削获得满足光学性能要求的自由曲面。本文提出了一种利用线性差动传感器(LVDT)实现高精度接触式自由曲面在位测量的方法。该方法结合两自由度快速刀具伺服系统,实现了基于快速刀具伺服(FTS)的自由曲面车削加工的误差补偿。试验结果表明,该技术将自由曲面的加工精度提高了20%,表面粗糙度降低18.1%,解决了FTS系统与机床运动的同步问题,可补偿机床xyz三向运动误差,可用于自由曲面加工误差的修正。该方法还可用于不对称幅度较大的曲面或硬脆性材料的加工等,故促进了高精度光学自由曲面的推广应用。

Fast Tool Servo （FTS） diamond turning technology usually can not obtain satisfactory optical freeform surfaces by one-step turning because many error factors will drop the fabrication accuracy of freeform surfaces. Therefore, a higher precise contact in-side measuring method for freeform surfaces was proposed by using a Linear Variable Differential Transformer （LVDT）. By combination with a two DOF fast tool servo system, the error compensation technology for optical freeform surfaces machined by fast tool servo diamond turning was implemented to enhance the fabrication accuracy. The experiment results show that the form accuracy has improved by 20% and surface roughness decreased by 18. 1% with the proposed error compensation technology. This technology solves the synchronization between FTS system and tool movement, compensates movement errors in xyz directions of the machine tool and can used in correction of the machining errors of freeform surfaces. Moreover, it can be used to cut the large asymmetry surfaces and brittle materials, so that promotes the applications of high precision freeform surfaces.