Everything around us changes rapidly and outside-the-box thinking is the order of the day. Lateral thinking by the designers will evoke simple solutions, even for complex problems. This case is a typical example of that.
Using a chill is a common concept to avoid/shift porosity in gravity casting. One of the automotive application parts, an oil filter adaptor, which has porosity and leak proof requirements, was a challenge and CRP thought of implementing this "chill" idea.
Figure 7a - Model showing the concept of copper chill with in the core pin.
One of the critical bore areas of this part had the issue of last fill as well as shrinkage porosity issues. The core pin at this location was very small and cooling systems for it was complex and costly. Therefore it was decided to use a copper chill inside the core pin to rapidly take away the heat from the tip if the pin through the center portion (Figure 7a).
The condition was simulated with the emerging technique, called thermal die cycling simulation, and the results were encouraging (Figure 7b).
Figure 7b - Thermal Die Cycling Simulation results without (left) and with (right) the copper chill.
With the copper chill.
Without the copper chill.
The chill was implemented and the actual measured temperature profiles of the core pin with and without chill were found within 20?C of the simulation results, and the correlation was amazing . The porosity levels were significantly reduced from above 20% to less than 5%.
The key aspect in this design was to ensure proper contact of copper with the die material on all sides and at all times. This was ensured in the manufacturing in order to achieve this remarkable result.