A study on separation behavior of press‐molded glassware from a thermal engineering viewpoint: Correlation of separation forces to the interface temperature between the mold and the glass

Abstract This paper deals with the separation behavior of a press‐molded glassware from the pressing mold surface. Since the separation of the glass from a mold surface affects the transcription of the glass shape from the mold, it is desirable to control the separation behavior in the practical press‐molding of glassware. The separation or sticking of the glass is mainly influenced by thermal pressing conditions in practical molding. Hence, separation forces during the demolding process between glass and mold were measured under various pressing conditions. The results show that, under certain conditions, the glass sticks on the pressing surface of the mold even after the mold is removed from the pressed glass, and that the separation (sticking) force increases with rising initial temperature of glass and mold, increasing the pressing pressure, and with elongation of pressing duration. In order to interpret the obtained results, the separation forces were correlated to the interface temperature between glass and mold at the end of the pressing process. The correlation shows that the sticking force becomes evident when the interface temperature exceeds a certain temperature. Under the experimental conditions, the threshold temperature was about 660 °C, and was slightly lower than the “softening temperature” of the glass used. From the results, it is concluded that the separation behavior of a press‐molded glassware is dominated by the interface temperature between glass and mold at the end of the pressing process. © 2001 Scripta Technica, Heat Trans Asian Res, 30(8): 660–675, 2001