Method of forming sagging mold from a glass ceramic
AssigneeCorning Glass Works
InventorWendell C. Andrews
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Abstract
A relatively thin, smooth surfaced mold of low thermal expansion material which exhibits non-sticking qualities is disclosed for contouring glass articles, such as by sagging a preform to the contour of the mold. In addition, a method of forming such molds with a desired surface contour is disclosed.
Claims6
A method of forming a thermally and dimensionally stable sagging mold of low thermal mass for repeatably sagging glass articles to a desired surface contour which comprises, forming a master mold with a surface contour corresponding to that desired for the finished sagged glass articles, grinding a sheet of glassy material which is crysatllizable upon the application of heat into a highly refractory glass-ceramic material which can withstand sagging cycles of up to at least 730.degree. C. without failure to a desired thickness, positioning said ground sheet of glassy material upon said master mold, applying heat to sag said sheet of glassy material into conformity with the contoured surface of said master mold, applying additional heat to crystallize said sheet of material into a glass-ceramic material having a maximum coefficient of thermal expansion of about 20 .times. 10.sup. -7 /.degree.C., and cooling said sagged and crystallized sheet to form a dimensionally stable rigidified glass-ceramic sagging mold.
A method of sagging a glass article to a desired surface contour which comprises, providing a sagging mold of glass-ceramic material having a predetermined contour corresponding to the desired surface contour of the finished sagged article, positioning the article to be sagged upon said sagged mold, subjecting the article and mold to a thermal cycle and sagging the article into desired conformity with the surface contour of said mold, maintaining the dimensional stability of said mold during the heat-up and cool-down of the sagging cycle with said mold having a maximum coefficient of thermal expansion of about 20 .times. 10.sup.-7 /.degree. C., and facilitating the dissipation of heat energy for effective thermal cycling by limiting the thickness of said glass-ceramic sagging mold to a maximum not substantially greater than one-half inch.
Dependencies are inferred from the claim text.