다수캐비티 사출금형의 러너형상에 따른 수지의 충전거동에 관한 연구

Abstract

The filling imbalance in injection molding process leads to distortion and increases product's internal stress. Unequal shrinkage rate and orientation by the filling imbalance bring about deterioration of product such as warpage and inequality gloss. The study on the filling imbalance in a multi cavity mold that was began at 1997's by Beaumont. He has been shown step by step reasons of the phenomenon. Nevertheless, a cleary solve of the problem has not been yet. However the present domestic studies about the filling imbalance classified the software method to minimize the problem by analyzing effective factors having influence on the filling imbalance and the hardware method to apply the runner core pin(RC pin) on diverging point of 1st runner in injection mold. A continual advanced methods for balanced filling is needed notwithstanding these former efforts because more high precision and quality product with μm unit is demanded according to injection molding industrial growth. In this paper, a study on the filling behaviors of polymer according to runner shapes in the multi-cavity injection mold was performed. The filling imbalance is investigated at a geometrical imbalanced and balanced runner system in multi cavity mold. The filling imbalance rate also by injection molding conditions has been investigated and various runner system for amorphous and semi-crystal plastic materials. In each chapter, the results of injection molding analysis and molding experiment are analyzing to refer demand for 3D CAE injection molding analysis software. This study is based on the results of reverse corner(sharp corner) effect that was released by Beaumont, Mckee and Hoover and cold slug well(groove corner) effect that was released by PIM(Precision Injection Molding) laboratory of Pukyong National University. Especially, a new runner system applied to results of filling balance rate according to runner corner shape effect and variable runner corner is suggested. Moreover, for case study an experiment was conducted with mold applied cavity of fork shape. Finally, in order to verify the validity of a new runner system for filling balance, it was experimented about the effect of runner corner shape on the molding's quality. The result of experiments show that the new runner system applied together groove corner and sharp corner made fine filling balance rate and good quality product.