Real Prototype – Realistic Casting?

Before start of production, many real castings are required for testing under realistic conditions. As with many of these prototype castings, the aluminum steering knuckle shown here was produced as a sand casting – a suitable process for low volume castings. The finite element analysis and durability calculations for a cyclic loading of the component point out the most critical locations. The failure of the prototype casting in a test run would lead to design changes: heavier cross-sections to better withstand the load.

However, the comparison of two virtual castings – the sand cast prototype and the low pressure die cast series casting – clearly shows different microstructures. Particularly the durability relevant dendrite arm spacing in the critical casting sections differ by 100 % for the two castings!

Knowing this, the designer can exploit the higher durability of the die cast series casting, even if the “real” prototypes would mislead him into moving in the wrong direction.

Secondary dendrite arm spacings depend on the casting process

The permanent mold series casting lasts three times longer than the sand cast prototype