형상적응형 냉각채널을 가진 균일/고속 냉각 사출성형 금형 개발에 관한 연구

Abstract

In recent, several research works on the development of the injection mould with a rapid and uniform cooling characteristics have been actively undertaken in efforts to improve productivity and the quality of the injection moulding process. After the advent of the rapid prototyping and tooling (RP&M) technologies, various attempts to apply the RP&M technologies to manufacturing of the injection mould. The preferred application of the RP&M technologies in the injection mould was the development of the injection mould with conformal cooling channels. The objective of this thesis is to manufacture an injection mould with conformal cooling channels for a plastic fan part using hybrid rapid tooling technology combining a laser-aided direct metal tooling (DMT) process with a post-processing. A proper design of the conformal cooling channels was obtained from three-dimensional injection moulding analysis using MPI V 6.1. In order to insert conformal cooling channels into the mould, the geometry of the mould was decomposed into base and moulding parts. The base part with guide slots was fabricated from a machining process. The copper pipes were inserted on the guide slots as the conformal cooling channels. The moulding part was manufactured from DMT rapid tooling process. Finally, a post-processing was performed to improve the surface roughness of the mould. The manufacturing time of the mould was nearly 191 hrs. Characteristics of the manufactured mould were investigated through the measurement of the hardness, the observation of micro-structures in the jointed region and the leakage test. The influence of the cooling time on the qualities of the mould product was examined via injection moulding experiments. The results of the injection moulding experiments showed that an optimum cooling time, which minimizes the positional error, the thickness error and the eccentricity of the moulded product is 13 seconds. In order to investigate efficiency of the designed mould, the results of injection moulding experiments for the designed mould were compared to those for the previously designed mould with linear cooling channels. The results of the comparison showed that cooling and cycle times can be improved nearly 35.0 % and 25.7 %, respectively. In addition, it was noted that the product quality can be remarkably improved when the designed mould was used.