A study of the influence of diecasting machine injection characteristics upon metal flow in runner: gating systems

Abstract

The object of the thesis is to examine the influence of machine injection systems,and of mould runner : gate systems,upon metal flow in the pressure diecasting process.to enable design of these to be optimized. An analytical framework covering those flow variables which significantly influence casting quality is developed for this purpose and experimental evidence offered in support. The work is presented in two parts: In part 1, an analysis of machine : mould influence upon flow rate, energy rate and flow state of the casting alloy is presented. Flow rate, (both of the casting alloy and mould gases), is an aspect of pressure casting which has received much attention in previous studies. Consequently in dealing with this aspect comparison is made, where appropriate, with any significant past work both as a means of correlation and also to resolve any anomalies which may exist. A theoretical examination of a number of machine : mould combinations is made, demonstrating the interdependance of injection system and (mould) runner : gate design in establishing flow conditions. Finally the analysis is applied to an experimental diecasting machine and mould and the results of this compared with measured performance. In part 2, a loss coefficient equation applicable to runner : gating systems is developed for use in the analysis of part 1. This is compared with reported information and 1-vi th the results of experimentation using a water model. The model is further used to examine state of flow through gating systems both as a corollary to the machine experimentation reported in part 1 and also to enable the flow state criteria proposed in the analysis to be assessed. A range of gating systems are used and flow is examined in both infinite and finite cavity conditions.