离心熔铸非球面镜镜胚面形偏差工艺参数的敏感性研究

离心熔铸技术在大口径非球面镜镜胚的制造方面具有独特优势。本文通过自行研制的缩比模型实验机进行试验,深入研究了离心熔铸工艺及成型镜胚质量,详细介绍了模具涂层的制备、离心熔铸的加热及冷却等工艺过程,制备了非球面镜镜胚模型。采用数值模拟与试验研究相结合的方法,对所得镜胚面形偏差工艺参数的敏感性进行了研究。分析了模具的热膨胀系数、镜胚冷却速率、直径及加热温度对面形偏差的影响,得到了偏差工艺参数的敏感性规律。通过对面形偏差进行两次迭代补偿,面形偏差值从-84μm降到33μm,补偿后的结果满足设计要求。采用离心熔铸技术,可以制备满足上表面垂直偏差在30~40μm范围内的非球面镜镜胚。

Study on sensitivity of surface deviation for aspheric mirror blank on centrifugal melting casting

Centrifugal melting casting technology has unique advantages in the manufacture of large aspheric mirror blanks. In this paper, the centrifugal casting process and the quality of the mold embryo were studied in depth by using a self-developed shrinkage model experiment machine. In order to obtain the required mirror blank, the processes of preparing the coating, heating, cooling and preserving the heat of the mold were introduced in detail. The influencing factors of shape deviation in the mirror blank production were studied by comparing simulation values with experimental results. The influence of the coefficient of thermal expansion, cooling rate, diameter, and heating temperature on the surface deviation was analyzed, and a mathematical expression relating these parameters to the deviation was derived. The compensation of the deviation was then calculated in two iterations, thus reducing the surface deviation from 84 to 33 μm. The compensation results met the design requirements. Using centrifugal casting technology, the aspheric mirror embryo can be prepared to meet the vertical deviation specifications of its upper surface in the range of 30~40 μm.