Chapin, T. and Walworth, V., "Cavity Fill Balancing Technique for Rubber Injection Molding," SAE Technical Paper 2015-01-0715, 2015, doi:10.4271/2015-01-0715.
Balancing the fill sequence of multiple cavities in a rubber injection mold is desirable for efficient cure rates, optimized cure times, and consistent quality of all molded parts. The reality is that most rubber injection molds do not provide a consistent uniform balanced fill sequence for all the cavities in the mold - even if the runner and cavity layout is geometrically balanced. A new runner design technique, named “The Vanturi Effect”, is disclosed to help address the inherent deficiencies of traditional runner and cavity layouts in order to achieve a more balanced fill sequence.Comparative analysis of molded runner samples reveals a significant and positive improvement in runner and cavity fill balancing when the Vanturi Effect is integrated into the runner design. Research results indicate that a viable and useable relationship exists between the fluid-like characteristics of the rubber flowing through the runner as the rubber flows into and through a specific geometric shape incorporated into the runner layout - which introduces the Vanturi Effect - resulting in improved balanced filling of the runners and cavities.