Investigation of the Stability of Melt Flow in Gating Systems

Abstract

Melt flow in four different gating systems designed for the production of brake disks was analyzed experimentally and by numerical modeling. In the experiments, molds were fitted with glass fronts and melt flow was recorded on video. The video recordings were compared with the modeling of melt flow in the gating systems. Particular emphasis was on analyzing local pressure and formation of pressure waves in the gating system. It was possible to compare melt flow patterns in experiments directly with modeled flow patterns. Generally, there was good agreement between flow patterns and filling times. However, the description of free liquid surfaces proved to be incorrect in the numerical model. The modeled pressure fields served to explain how specific parts of the gating systems cause instability and are a good tool to describe the quality of a gating system. The results show clearly that sharp changes in the geometry of the gating system causes pressure waves to form that eventually lead to defective castings. It is clear that sharp corners and dead ends in gating systems should be avoided, and that more streamlined, organic, or naturally pressurized designs based on fluid dynamic principles will are necessary to design gating systems for the production of high-quality castings.