Runner based flow imbalance effects during injection molding processes.

摘要

The use of the multi-cavity mold within the injection molding industry is widespread, it has reduced costs and increased throughput for almost every part made. The accepted standard runner design, the geometrically balanced runner, is also an industry standard yet has many drawbacks. Previous studies have shown that fill imbalance, thought to be eliminated from earlier runner systems, still exists within geometrically balanced runners. The common understood cause of these fill imbalances is the shearing of polymer as traverses the runner system, causing the polymer to heat and thin, making it no longer uniform within the runner. Melt rotation technology was developed to solve this problem, and prior studies have shown that it indeed can be used to cause uniform filling for a geometrically balanced design. However other effects of the shearing of the polymer are yet to be understood, including just how much it heats the polymer. Do the concepts of shear induced particle diffusion, well documented on the macro scale, transfer over to common engineering fillers? How do novel fillers, such as carbon nanotubes, respond to the large shear gradients within the runner system?;It is the objective of this research study to explore how all of these questions about shear induced problems effect injection molding. This study will look at documenting how thermal gradients are created, how fillers are distributed, and how mechanical properties are altered due to shear effects. Further, this project will try to mitigate any non uniform behavior through the use of melt rotation technology, and show it is a viable technology for providing better control during injection molding.