Compound Machining of Tungsten Alloy Aspheric Mould by Oblique-axis Grinding and Magnetorheological Polishing

With the increase in demand for various types of small-aperture aspherical optical parts, the machining of a small tungsten carbide alloy mould with high accuracy is not only required, but essential. Ultra-precision grinding is generally used to process the small tungsten alloy aspheric mould, but there are some grinding marks and surface defects left by grinding. Aimed at the problems above, this paper introduce a new compound processing technology which integrates ultra-precision grinding and oblique-axis magnetorheological polishing technology on the same machine tool. First, we developed the machining equipment of oblique-axis ultra-precision grinding and magnetorheological polishing, and then, we analyzed the surface accuracy, surface roughness, microstructure and subsurface damage of tungsten alloy aspheric mould after grinding and polishing. The experimental results indicated that the surface accuracy of workpiece was improved to smaller than 200 nm in PV value, surface roughness Ra was reduced to about 1 nm after using the compound processing technology.