Ultraprecision fabrication of large stamping die of Wolter mirror for an x-ray telescope by ELID grinding

This paper presents a ultra-precision manufacturing process of large stamping dies with confocal paraboloidal and hyperboloidal surfaces of Wolter mirror for an X-ray telescope. In order to improve the alignment of the two substrates and reduce the degeneration in imaging quality, two compound reflectors were formed from one thin substrate utilizing synthetic ELID grinding and arc-enveloped grinding method. Because the thin foil substrate was obtained by press forming, large stamping dies of foil substrate must be machined with high Fig. error and low roughness. In this ELID arc-enveloped grinding system, cast iron fiber bonded (CIFB) diamond wheels were 3-dimentional controlled to scan the workpiece and generate required surfaces. Through truing grinding wheel and ELID grinding for upper concave and lower convex stamping dies, attainable form accuracy, surface roughness were investigated.