The die designer is constrained by the part design as it is an end-user requirement, over which he has very limited or no flexibility. Generally, the design of an HPDC die starts with part modeling, followed by the shot design. Runners and overflows are the two important aspects of the die design in general and shot design in particular. The other aspects include the part orientation, parting lines, draft angles, etc. These aspects of the shot design give ample flexibility for the designer to optimize the overall die design to achieve the end requirements of the part.
Figure 1 - Potential defects of the four versions.
This case study is a simple example of a methodical approach towards the optimization of runners and overflows of a die casting shot design of an engine part, which needs to be porosity free and leak proof.
Analysis of Results
The flow simulations for defect predictions were done initially for the shot design versions V1 and V2, with variations in the runners. Version V3 was developed to optimize the runner. Finally, the version V4 is developed by redistributing the six large overflows into 10 smaller overflows(Figure 1).
This has resulted in the optimization of capturing maximum defects into these overflows without any addition of shot weight. The parts were approved on first trial itself.
This is the reason for flow simulation being an integral part of the design process.