光学元件数控单轴加工中的边缘效应控制建模方法

Modeling Method of Edge Effect Control in CNC Single Shaft Machining of Optical Elements

边缘效应严重制约了计算机控制光学表面成型技术(CCOS)的加工精度和加工效率,是亟待解决的技术难点之一。基于Preston方程,建立工具盘在加工工件边缘时的定量去除模型,是解决该问题的重要途径。将加工工件、工具盘尺寸,磨削压力、速度、时间,磨削点位等加工参量进行数学建模,建立边缘去除函数模型,精确计算边缘压力分布和磨削累计时间。随着工具盘在工件边缘露边量增加,工具盘压力呈指数级增长。工件磨削累计时间随工具盘中心点位不同呈现分段变化规律。研发单轴机数控设备,利用工具盘沿工件边缘母线点位移动方式,进行边缘效应控制研究。通过实验精确求出Preston方程比例系数k,验证模型仿真与实际加工结果吻合性,准确度达到91.9%。数控单轴机修边方法和建立的数学模型可以很好地指导实际研磨抛光过程。

Edge effect seriously restricts the processing accuracy and efficiency of CCOS,which is one of the technical difficulties needed to be solved urgently.An important approach to solve this problem is to establish a quantitative removal model of tool pad based on the Preston equation on the edge of the workpiece.The model includes some process parameters such as the workpiece size,the tool pad size,the processing pressure,velocity,time and position.The model calculates accurately the edge pressure distribution and the processing cumulative time.The processing pressure increases exponentially with the edge exposure area of the tool pad on the edge of the workpiece.The accumulated processing time of workpiece presents stage variation with the central point of tool pad in different workpiece sections.A single shaft machine with numerical control function has been developed.Combining with the established model,the machine is used to control edge effect effectively.The scale coefficient k of Preston equation is worked out in the experiment firstly.The model is in good agreement with the actual experiment results,and the accuracy can reach to 91.9%.The edge effect control method with the CNC single shaft machine and the relative model are well in guiding the actual grinding and polishing process.