Hits:

Indexed by:期刊论文

Date of Publication:2010-10-01

Journal:CHINESE JOURNAL OF MECHANICAL ENGINEERING

Included Journals:SCIE、EI、CSCD、Scopus

Volume:23

Issue:5

Page Number:553-559

ISSN No.:1000-9345

Key Words:injection molding; shrinkage displacement; visual mold; light transmission

Abstract:The existing research on shrinkage of the injection molded plastic part mainly focuses on various shrinkage ratios of the part dimensions, and the relevant experimental studies belong to mere dimension measurement after demoulding. Obviously, measuring after the plastic part is demoulded from the cavity can not offer shrinkage displacements of points on the plastic part. However, shrinkage displacements of points on an injection molded plastic part are essential for exposing the inner relation among shrinkage ratios of various dimensions of the part. So visualization of the in-mold plastic part which can indicate the location relationship between the part and the cavity is needed. In this paper, a visual injection mold was fabricated by adopting the half mold structure and light transmission manner. With the visual mold, in-mold shrinkage images of injection molded plastic parts were photographed after the plastic part stayed in the injection mold for 24 h. By means of digital image processing of the in-mold shrinkage images, the experimental data of shrinkage displacements of points on injection molded parts were researched. From the experimental data, it is found that shrinkage directions of points on an injection molded part are related with both positions of the gate and of the part centroid, and either the gate or the centroid will exert more influence on the shrinkage direction of some point which is closer. Furthermore, some point at the later filled area has more shrinkage distance than the point at the earlier filled area. Combination of shrinkage directions and shrinkage distances of points on an injection molded part determine shrinkage ratios for various dimensions of the part, and shrinkage directions are more influential to shrinkage ratios of dimensions. This experimental research of shrinkage displacements offers a unique approach to understand the shrinkage principles of injection molded parts.