圆弧金刚石砂轮三维几何形貌的在位检测和误差评价

针对非球面光学元件加工对圆弧金刚石砂轮形状误差测量的需求,提出了砂轮三维几何形貌在位检测与误差评价方法。建立了砂轮外圆面螺旋扫描轨迹测量数学模型,利用位移传感器获取了砂轮表面轮廓数据;对得到的数据匀滑滤波后沿圆周展开并进行插值处理,得到砂轮三维几何形貌。然后,根据非球面平行磨削加工特点,提出评价圆弧砂轮形状精度的指标。通过提取三维几何形貌轴截面轮廓,进行最小二乘圆弧拟合得到不同相位处的圆弧半径与圆心坐标,并由误差分离获得砂轮表面圆弧的圆度误差、圆周跳动误差及轮廓圆心轴向偏差。最后,对非球面加工圆弧金刚石砂轮进行检测,获得了砂轮的三维几何形貌以及多个关键尺寸及其误差数据:即圆弧金刚石砂轮的平均圆弧半径为55.442 3mm,半径波动极差为0.16mm,中央±8mm环带内圆弧的圆度误差约为5μm,圆周跳动误差约为2μm,截面轮廓圆心轴向位置相对偏差为0.008mm。根据检测结果,进行了大口径复杂非球面磨削实验,得到的元件面形P-V值为4.62μm,RMS值优于0.7μm,满足工程的实际需求。

3D geometric topographic measurement and error evaluation of arc diamond wheel

For the purpose of detecting 3D geometric topography of an arc diamond wheel precisely and efficiently in aspheric element processing, the methodology of on-machine measurement and the error evaluating of 3D geometric topography were proposed. Firstly, the mathematical model of screw-scanning track for the diamond wheel was established, and the profile data of the diamond wheel were acquired by a displacement sensor. After data filtering and interpolating, the 3D geometric topography of the diamond wheel was established. According to the feature of aspheric parallel grinding, some parameters to criticize the shape accuracy of arc wheel were put forward. By extracting the wheel profile of the axial direction, the arc radius and center coordinates were calculated by least-square circle fitting. And by error segregating, arc error, circular runout error and the deviation of profile center for the diamond wheel were extracted. Finally, an arc diamond wheel in aspheric element processing was measured experimentally. Some key dimensions and errors of the diamond wheel were achieved. The average radius of the wheel is 55.442 3 mm and the fluctuation range of radius is 0.16 mm. The arc error in the girdle of ±8 mm is about 5 μm, the circular runout error is about 2 μm and the relative deviation of profile center is 0.008 mm. By using those measured data, a large scale aspheric optics grinding experiment was performed and results show that the surface errors(P-V and RMS) of the element are about 4.62 μm, and below 0.7 μm, respectively, which satisfies the engineering requirements.