Alternative materials to shorten injection mold manufacturing and molding cycles

Abstract

This paper investigates mold materials for polypropylene (PP) injection molding, including CuBe alloy (high thermal conductivity), AISI P20 mold steel (the conventional material for injection molds), and polyurethane resin (rapid tooling). Characterization of molded parts involved microstructural analysis, tensile tests, warping, and degree of crystallinity assessments. The results show that the higher thermal conductivity of the mold’s inserts reduced the injection molding cycle time and produced thicker skins, which resulted in smaller spherulite sizes in the core of the samples, reduced the crystallinity degree, and consequently reduced the maximum strain property. The thermal conductivity of the molds’ inserts was shown to be more significative than the skin thickness and mold temperature for the size of the spherulites when they are formed. In addition, CuBe alloys showed to be a strong competitor with additive manufacturing-produced molds with conformal cooling channels to reduce injection molding cycle time.

Keywords:
CuBe alloys; injection molding; mold materials; processing cycle time