Robust Design Optimization of High Pressure Die Casting to Produce Piston Rods

N. Gramegna, F. Lago, G. Scarpa, P. Bortolato

L. Bellati

Automotive components are getting more and more complex in shape, with high performance demands, and at the same time less defects and an narrow margin of error; in other words, the design of automotive components requires a combination of acceptable cost, low weight, appropriated mechanical properties, structural integrity and easy production.
To achieve these objectives, the Design Chain approach, for metal casting processes and mechanical properties behaviour, based on optimisation tool, is increasingly used in consideration of  the solutions and the process optimisation provided.
One of the most relevant and successful innovations on recent years, and one which this article focuses on, is the CAE application to optimise the well known foundry process, e.g. high pressure die casting (HPDC), in agreement with the mechanical properties requirements.
CAE tools, like MAGMASOFT and its optimisation module MAGMAfrontier, are evolving to support the design during the research of the best engineering solution. The virtual prototype approach is interesting in particular in case of component subjected to high cycle fatigue and sensible level of stress like a aluminium alloy Piston Rod.
In general, the component design comes from the structural FEM simulation, after the mechanical behaviour verification, and it is a geometry input for the manufacturer. The mechanical properties of HPDC components can be affected by gas porosity, shrinkage and other different defects as well as oxides or cold shots. It’s means that the HPDC is an attractive process for high level of productivity but its set up and the optimisation the die design are a very complex tasks.
The problem can be divided in sub-tasks :

  1. Traditional structural analysis of the designed piston rod to verify which are the critical zones where there are the maximum compressive and tensile stress and to evaluate the stress level compared to the ultimate tensile strength of the material;
  2. Optimization of the production process (take advantage of Automatic Optimization technology) for defining the dies and process parameters suitable for the production of Piston Rod maximizing its quality;
  3. Advanced structural analysis by exploiting the mechanical properties of the cast from the process analysis to make the final structural verification and validating the production process.

The article aims to show the innovative techniques for the design using the integration of virtual simulation tools to optimize the quality of the finished product, indicating the basic