The Measuring Method In Injection Molding With Ultrasonic waves

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This paper describes the measuring method in injection molding process by using ultrasonic waves. A method of monitoring the flow and cooling behavior of polymer melt, methods of measuring the crystallinity of the molded plastics of thermoplastic, the injection pressure in the cavity, and the locking force, and a method of detecting the cause of the thin flash have been developed.In this study, following results have been obtained. (1) Flow behavior of polymer melt can be obtained by the variation of the amplitude of reflected, waves. (2) Cooling behavior and the temperature distribution of plastics in thickness direction can be obtained by the travelling time through the solid and the liquid phase of plastics in the cavity. (3) The crystallinity can be obtained indirectly by measuring the longitudinal sound velocity. (4) The reflection echo ratio of ultrasonic waves at the interface between the mold surface and the metal foil placed on the mold surface is proportional to the cavity pressure. (5) The behavior of the locking force and the cause of the thin flash can be determined by measuring the reflection echo ratio at the parting surface of the mold.