Optimization of diecasting runner-gate system

Quality of diecasting components is strongly influenced by the fluid-dynamics filling. Consequently, a good design of the die cavity is fundamental to avoid turbulence, resulting in casting defects, and to allow the production of very complex castings. Particularly, the gate system is one of the most important mould part to be controlled, to guarantee an effective die filling. Commercial software for the simulation of mould filling and casting solidification represent an important tool of analysis and a good help for a correct design. The aim of this work is to define the effect of the gating system geometry on the energy loss during filling of diecasting dies and also on their pattern flow. The study was approached by the use of two numerical simulation software: Calcosoft® (specific for 2D problem) and Procast. The attention was focused on fan feed gates, considered to be the most widely used in high pressure diecasting. The first part of this paper describes the research of a relationship between energy dissipation and gate design, in terms of gate convergence angle, section thickness, sketch, etc.. Initially a few 2D simple geometries, characterized by different shape, were investigated, considering a typical aluminun-silicon alloy for the data needed for simulation. Subsequently, as a function of the results previously obtained, the study was extended also to 3D geometries, to evaluate the effect of the fan feed shape, of the ratio between runner and gate sections and finally of the runner width/thickness ratio. A first important result obtained by the simulation analysis is that an optimization of the gating system cannot be obtained through the variation of a single parameter; a compromise must be researched in order to take into account the interaction between every factor. So, small variation ranges, for each geometrical parameter, were fixed to avoid bad configurations of the gate-runner system. In other words, guidelines for a good diecasting die design were attained. To validate the results achieved, the approach was extended also to a real geometry of a diecasting die for the realization of flat tensile strength samples of different thickness, demonstrating a performance improvement of about 30%. The design guidelines obtained are nowadays used for the realization of an experimental diecasting mould for future tests.