Time and temperature in pressing sheet-glass components

Two alternative approaches can be adopted in determining the pressing time for sheet glass. The first is to choose the pressing time in relation to the maximal stress relaxations as stresses arise during pressing. The elastic after-effect is balanced by an appropriate increase in the curvature of the components. The chilling accompanying the process can be determined and balanced by some superheating of the glass before pressing. The second is to set an acceptable level for the chilling and determine the time in which this occurs (t0); the stress relaxation in t0 is estimated and allowed for in choosing the shaping curvatures. A method and nomogram for the first approach are presented. They can be used in deciding the pressing conditions for thin glass. 2 refs.