Morphology Evolution and Elimination Mechanism of Bubble Marks on Surface of Microcellular Injection-Molded Parts with Dynamic Mold Temperature Control

Abstract

The morphology evolution and elimination mechanism of surface bubble marks on microcellular injection-molded parts with dynamic mold temperature control were investigated. It is found that with the increase of mold temperature, the surface bubble marks with morphology of rolling ribbons and uneven gullies formed in low mold temperature conditions gradually evolve into thin and tiny strips and finally disappear. The evolution of surface bubble marks under high mold temperature conditions undergoes a process from generation to disappearance, that is, the melt first forms a surface with originally generated marks; then the bottom melt of the generated marks is continuously pushed out and forms island protuberances, thus gradually dividing and reducing their space and volume; finally, the original marks are eliminated. Escaping from the gap between mold and melt and redissolving into the high-temperature melt are the main ways the gas in the original surface bubble marks disappears.