Experimental Study on Sink-Mark Generation on the Press-Formed Glass under the Asymmetrical Cooling Condition.

Abstract

In this paper, we present an experimental study on the sink-mark generation of the press-formed glassware affected by the asymmetry of the thermal condition during the press-forming process, bottom surface of the press-formed glassware is in contact with the bottom mold during entire forming process, while the upper surface is cooled by the plunger mold only in the short pressing duration. The depth of sink-marks appear on the upper and bottom surfaces were measured for various forming conditions, and the obtained results were summarized as follows : (1) The depth of sink-mark on the upper (plunger-mold side) surface decreases with lowering the initial temperature of plunger mold and with elongation of pressing duration, while the sink-mark depth on the bottom surface is hardly influenced with them. (2) Lowering the initial temperature of bottom mold enhances the cooling of whole glass in the mold cavity, and thus results in reducing the depth of sink-mark on both surfaces of the glassware. However, when the initial temperature of bottom mold is set under 460°C, miniature wrinkles appear on the bottom surface of the glass, and the sink-mark depth on the upper surface increases with lowering the initial temperature of the bottom mold. (3) The sink-mark depth on the bottom surface decreases with elongating the take-out time, but sink-mark on the upper surface becomes deeper at the same time.