Development of High-Density-Polyethylene-Based Thick Multi-Reducer Injection Mold Incorporating Cooling Analysis Technology

Abstract

A large high density polyethylene (HDPE) multi-reducer is designed as a multi-joint pipe with seven different thicknesses, as a part for connecting HDPE pipes of different diameters. The multi-reducer prepared in this study weighs more than 30 kg per product, it has a wide range of thicknesses reaching 180 mm in the thickest part; till now, no attempts have been devoted toward the production of such a large multi-reducer via molding. The result of cooling analysis of the 3D mold designed to obtain a high-quality product showed that because of the large amount of the raw material injected into the mold, pores and defects such as shrinkage, depression, shape dimensional deformation are formed owing to non-uniformity in the temperature distribution. In order to verify the theoretical shrinkage and cooling deformation that occur during thick injection molding, the test product was measured, and the design technology considering the final shrinkage and strain was reflected in the cavity and core revision design. The thick products with a large difference in thickness are more deformed during cooling; therefore, we focused on the cooling channel design. Through a series of experiments, we were able to successfully develop a HDPE-based thick multi-reducer for large products that has never been prepared before.