Design and optimisation of runner and gating systems for the die casting of thin-walled magnesium telecommunication parts through numerical simulation

A well-designed runner and gating system is very important to secure good quality die castings through providing a homogenous mould filling pattern. Numerical simulation is a cost-effective tool in the design of runner and gating systems to visibly analyse the mould filling process. A thin-walled magnesium telecommunication part was selected to be hot chamber die cast and a numerical simulation technique was applied for the optimisation of the runner and gating. Two types of runner and gating systems were designed and analysed. A preliminary design with a split gating system led to a swirling filling pattern and insufficient central flow, which prematurely closed the edges and left the last filled areas falling into the inner portion of the part. It resulted in a high possibility of air entrapment in the casting and the design was not proper for the part. The design was improved by using a continuous gating system and a bigger size runner. The gate area was increased and the gating speed was slightly reduced. Numerical simulation showed that the new design provided a homogenous mould filling pattern with the last filled areas being located at the upper edge of the part, where overflows and vents were conveniently attached. For the study, die inserts for both designs were fabricated. A series of casting experiments were conducted. The short shot filling tests proved that the simulation results matched the actual casting results very well. Good quality thin-walled telecommunication parts with sound microstructure were produced based on this optimised runner and gating system.