Case Study: Main Bearing Cap

Process: Conventional powder metallurgy

Material: FC-0205 mod. copper steel

Density: 6.70 g/cc

Ultimate Tensile Strength: 480 MPa

Yield Strength: 410 MPa

Main Bearing Cap
A 2018 Grand-Prize winner in the Automotive—Engine Category

End Use and Function

This copper-steel main bearing cap made for Fiat Chrysler Automobiles (FCA) is used in the 2.0 L aluminum turbocharged four-cylinder FCA engine launched in the Alfa Romeo Giulia. While PM main bearing caps have dominated engine design for more than two decades, the design of this component breaks new ground. Developed from the start using powder metallurgy (PM), the innovative weight reduction design was developed to compete with cast iron alternatives while maintaining a competitive cost.

Fabrication

The overall shape of the component is unique for PM main bearing caps. The sculpted shape required for weight reduction also required a step change in the manufacturing process. The powder transfer required to form a defect-free part requires the near perfect choreographing of upper and lower tooling. Both product and process technology advances were necessary to produce a robust product.

The component required the use of multiple upper and lower levels consisting of 5 punches on both upper and lower as well as core rods and significant powder transfer. Requirements for engine weight reduction drove the designers to an “upside down” sculpted version to realize weight savings and required substantial powder transfer to form the crankshaft bore.

Results

The novel design delivers a part that is 23% lighter than previous versions and offers a 10% better fatigue strength.
The unique shape has exceeded customer strength requirements; however, it’s important to note that the early relationship between end user and fabricator was pivotal for successfully developing this component. The early design was intended for a traditional bore down compaction process, but through discussion between the end user and fabricator, a more innovative approach was taken that resulted in component benefits.