사출성형 제품의 기능적 특성 향상을 위한 이중사출성형 금형 개발에 관한 연구

Abstract

One of recent issues related to an injection moulding process is the improvement of the product quality and the productivity through the innovation of the process and the mould design. Double-shot injection moulding process has been developed to improve the quality of the mould product and the productivity of injection moulding process. In addition, the double-shot injection moulding process can assign the desired functionality to the moulded product through a successive moulding of two types of resins with different compositions and colors. The objective of this thesis is to develop double-shot injection moulds for the improvement of functionality of plastic parts. A rotating type of the double injection mould with an index axis was adopted to reduce a manufacturing time of the plastic part. In this thesis, two types of double-shot injection moulds were designed. The first type was a multi-sliced double-shot injection mould incorporating with a proper three-dimensional conformal cooling channels in a hot spot region. Preliminary three-dimensional numerical analysis was performed to estimate a hot spot region, in which the residual temperature was higher than other region of the moulded part, in the mould product. The three-dimensional conformal cooling channels was assigned in the vicinity of the hot spot region. A proper design of the three-dimensional conformal cooling channels was chosen through the investigation of the influence of the diameter and position of the conformal cooling channels on the temperature distribution and the product quality. The second type was a double-shot injection mould for a human-friendly computer mouse with two different materials according to the required functionality. The human-friendly computer mouse was designed to be manufactured from the injection of a TPE (Thermoplastic elastomer) resin with a soft property on the base structure consisting of ABS (Acrylonitrile Butadiene Styrene) plastic part. Through the injection moulding and over-moulding analyses, a proper double-injection moulidng conditions were estimated. Two types of the double-injection moulds were fabricated to perform the injection moulding experiments. The first type of double-injection mould was divided into conventional and hot spot regions. The core of the hot spot region was manufactured from the hybird metal rapid tooling technology. The results of injection moulding experiments for the first type of double-injection mould showed that the multi-sliced mould can remarkably improve the product quality and the productivity in comparison with the conventional mould. The results of injection moulding experiments for the second type of double-injection mould showed that a proper human-friendly computer mouse with the improved emotional characteristics can be manufactured when the proposed mould design and moulding condition were adopted.