Objective: Industrialisation of a structural component that is required to have good oil seal properties for application in the automotive sector

Process: Die-casting technique; alloy used: Alsi9Cu3 (UNI EN AB 46000)

Requirements: Design a mould with at least 2 cavities; avoid porosity in a well-defined heavy section to be subjected to mechanical processing

Results: Guaranteed component integrity; 4-cavity mould with significant reduction of operating costs

Client: Magna, in cooperation with Galba s.r.l and Alpress s.r.l.

The action

To identify the most performing solution, we assessed various possibilities.
First, we set aside the idea of simulating a casting sprue by using the lower part of the piece because the Material Trace data indicated that the two runners did not work properly and resulted in non-homogeneous mould filling with material that tended to detach itself. Thanks to Hot Spot we identified the criticality of hot spots that formed due to the molten metal’s incapacity to occupy the entire volume once solidified. The positioning of a squeeze pin close to the heavy section could have solved the problem, but the presence of trapped air would have limited its benefits. We then decided to study a targeted casting on the part’s heavy section so as to reduce to a minimum the shrinkage porosity and reduce entrapped air. To do this, we had to add another insert mechanism and so, in order to lower operating costs, we decided to add 2 profiles while choosing to use a 4-cavity mould.
The simulation with Material Trace showed that with this casting solution the melt was “accompanied” evenly. Air Pressure data showed that the new layout brought air outside the part so as to be vented. Porosity showed substantial reduction in porosity. Based on the results of the simulation, we positioned a chill vent in the area that filled last with the molten metal, thereby drastically reducing the residual air inside the die, as also confirmed by the MAGMA 5 data. At that point, we designed the 3D version of the mould with its heat regulation circuits, designed with the aim of keeping a not too high temperature so as to reduce cycle time. We then simulated 9 cycles to make sure the heat range of the mould stayed around 200°C.

Results:

Thanks to the solutions adopted, the porosity value was lowered significantly. It was fundamental to add a gate with an additional mechanism to work better on the third phase of the press. The cost of the mould was counterbalanced by the savings obtained by adding two additional profiles. The client’s requirements were therefore met:

• the component’s integrity in the critical area was ensured
• a mould of 4, not 2, cavities was obtained, with considerable savings in operating costs.