Geometric-Structural Study of the Accelerated Degradation of Mold Cavities for HDPE Injection

In this work, we present the case of a series of injection cavities that showed accelerated degradation. A combination of computer-aided engineering design (CAED) techniques contributed to deduce the failure origin, which may be used to increase the lifetime of the studied product. The failure in the metallic material of the injection cavity was due to degradation in the quality of the final product that was made of high-density polyethylene. The failure generated non-expected protuberances in the final product. The study was complemented by scanning electron microscopy that confirmed the initial failure hypothesis. Using the finite element method (FEM), a series of load scenarios was carried out that gave further support to understand the origin of the failure. Due to the appearance of microcracks at the surface of the injection cavity, thermal and mechanical stresses were shown to be the responsible of plastic deformation at the injection cavity. We also propose a redesign of the piece to avoid the existence of the detected damage in the injection cavity and the final product.