Categorization of Failures in Polymer Rapid Tools Used for Injection Molding

Abstract

Background—Polymer rapid tooling (PRT) inserts for injection molding (IM) are a cost-effective method for prototyping and low-volume manufacturing. However, PRT inserts lack the robustness of steel inserts, leading to progressive deterioration and failure. This causes quality issues and reduced part numbers. Approach—Case studies were performed on PRT inserts, and different failures were observed over the life of the tool. Parts molded from the tool were examined to further understand the failures, and root causes were identified. Findings—Critical parameters affecting the tool life, and the effect of these parameters on different areas of tool are identified. A categorization of the different failure modes and the underlying mechanisms are presented. The main failure modes are: surface deterioration; surface scalding; avulsion; shear failure; bending failure; edge failure. The failure modes influence each other, and they may be connected in cascade sequences. Originality—The original contributions of this work are the identification of the failure modes and their relationships with the root causes. Suggestions are given for prolonging tool life via design practices and molding parameters.

Analysis of Raised Feature Failures on 3D Printed Injection Moulds

“…Based on the current findings and previous work [22], the failure of raised features for 3DIM is classified as shown in Table 10.…”

“…In the majority of cases, resin manufacturers specify a mould temperature which varies based on the type of resin but was generally found to be between 40-80 • C. Using these mould temperatures with 3DIM would lead to softening of the 3DIM as they are above the glass transition temperature (T g ) of most 3DIM materials [24]. In our previous work, we also identified three major failure modes; surface failure, avulsion and feature failure [22].…”

“…In certain cases, surface smoothening of 3DIM was observed. The smoothening resulted in lower ejection forces in some cases, but in a majority of the cases resulted in excessive flashing [ 22 ].…”

“…Using these mould temperatures with 3DIM would lead to softening of the 3DIM as they are above the glass transition temperature ( T g ) of most 3DIM materials [ 24 ]. In our previous work, we also identified three major failure modes; surface failure, avulsion and feature failure [ 22 ].…”

Special Issue on “Computational Methods for Polymers”

“…Bagalkot et al [13] present case studies on performing polymer rapid tooling inserts and observing different failures over the life of the tool. They identify critical parameters affecting tool life, and the effect of those parameters on different areas of the tool.…”