Analysis and optimization of compression glass molds: Tumbler
Research in the field of glass molds and its effects on the final product has been done in the past based on field experiments with prototypes. Some previous studies have established the need of computer application packages as tools of analysis and comparison of the effect that the changes in mold design. This study proposes the application of computer aided methods to obtain optimized and thermally balanced glass molds. This particular study, as developed, was limited to axissymetrical models, specifically for a tumbler, and was not an exhaustive design for a general manufacturing system. During compression glass molding process, molten glass, at a temperature of around 1050 °F, is compressed between a plunger and a mold. Since the molten glass is almost in a fluid condition, it readily takes the shape of mold/plunger, as it is squeezed between them. During the mass production of glassware products, using compression glass molding technique, the plunger and the mold are exposed to high temperature and pressure conditions. This, coupled with regular normal wear and tear results in the formation of cracks and distortions on the mold and the plunger, which in turn affect the quality of the molded glass part. The molding process can be simulated on computers using various software programs. In this study the models of molding parts were created using I/EMS (Intergraph Engineering Modeling System). Using Finite Element Analysis, the mold bottom and the plungers were subjected to the actual boundary conditions provided by the manufacturer. Thermal stresses developed can be reduced by design optimization, either increasing the surface area of the plunger and the mold or altering the boundary conditions suitably. After carrying out various iterations, an optimized design was obtained where the stress levels are reduced considerably without altering the product significantly. The bottom portion of the plunger was constrained in all three coordinates. Thermal boundary conditions were applied on the surfaces of the plunger. Since the outside surface of the plunger comes in direct contact with the molten glass, a temperature of 1050 °F was applied on the outside surface, whereas a temperature of 200 °F was applied on the inside surface. Moreover, since the plunger is forced into the mold with pressure, a pressure boundary condition of 35 psi was applied to the top surface of the plunger. By varying the thickness of the plunger walls, it was possible to reduce the difference between the highest and the lowest stress values and get more uniform thermal structural stress contours for the plunger. As an initial attempt for further research, an analysis to study the glass forming process and the effects of changing the thickness of the plunger walls in the die fill, was made. It is still necessary to determine strain-stress characteristics of glass at melting temperatures and discuss the effectivity of this approach.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:glass molds axissymetrical models intergraph engineering modeling system finite element analysis
Date of Publication:01/01/1997