Weld‐lines and its strength evaluation in injection molded parts: A review

Abstract

AbstractInjection molding manufacturing is immensely popular nowadays because of its excellent manufacturability for complex designs produced from a wide range of different engineering plastic materials. Weld‐line is a defect that arises in injection molding when two or more flow fronts collide. The weld‐lines are undesirable from both aesthetic and functional points of view and their effect is different for varied materials, process conditions, loadings, forms of weld‐line, etc. The presence of a weld‐line weakens components locally due to insufficient intermolecular diffusion, v‐notch formation, fiber anisotropy, insufficient process conditions, and so on. When a component is under load, crack propagation usually begins with a weak weld‐line area. Therefore, the designer should anticipate the presence of weld‐lines and their strength to avoid failure of components during operation. In this article, the review of published research work on weld‐line formation during injection molding has been summarized. The review focuses on the phenomenon of weld‐line formation, the type of weld‐lines, and the importance of weld‐line evaluations. The theoretical, experimental, and computational approaches to analyzing weld‐line and its strength are covered in detail. At last, methods for reducing weld‐lines and increasing the strength of weld‐line area have been discussed. This review also gathers data on weld‐line strength with respect to different materials.Highlights Details of weld‐line formation and its types. Importance of weld‐line evaluation. Methods of weld‐line strength evaluation. Methods of reduction of the number of weld‐line and its effect. Summary of weld‐line strength for different material.