Practical Problems in Forming

Abstract

In practice, forming of glass depends not only on the application of these exterior pressing and stretching forces but also on the force of gravity. Practical forming is a complex process and is strongly influenced by shearing forces from the viscous edges. In the transition regions of the viscous, plastic and solid states, not only the elastic deformations are determinant, but particularly also the technical flow processes. It is always assumed that during a change in shape the heat of the glass is extracted by the molds and to the outside air in order to increase the glass viscosity and to obtain the desired shape after removal of the molds. A forming machine by using appropriate tools has thus the task of effecting the change in shape and directly or indir~ctly achieving heat