A novel CNC aspheric grinding machine

Aspheric surface can be thought as being enveloped by a series of spherical surfaces with their centres on the same axis but having different positions. These spherical surfaces are tangent with the aspheric surface. We have manufactured a Φ600 CNC aspheric grinding machine with this novel operating principle. We choose δp , ε and αp as the key parameters of our grinding machine. δp is the distance between the cup-shaped tools' bottom and the vertex of the aspheric surface. αp is the rotational angle of the cup-shaped tool. ε is the space angle of the cup-shaped tool during the fabrication process of convex aspheric surface. Using this grinding machine, we can fabricate a conic concave aspheric surface continuously about three hours. But we need change the cup-shaped tool one time when we fabricate a conic convex aspheric surface in also about three hours. Our grinding machine can also be used to fabricate high-order aspheric surface. We used this machine fabricating a RC telescope system's primary and the secondary mirror. The PV-value is less than 5μm for the primary Φ350 concave hyperbolic aspheric surface which departure is about 55μm. We can polish and finish this aspheric surface with these residual errors easily. The manufacturing cost of the machine is about 300,000 RMB which is 1/10 of the LOH's product with the same maximum aperture of workpiece.