Cast-In Brake Disc – An affordable lightweight design for passenger car brake discs

To meet evolving automotive demands, Fritz Winter is developing new lightweight brake discs. While alternatives to traditional cast iron discs exist, aluminum compound versions are too costly, and mechanically joined steel hat discs present complex assembly and tolerancing challenges. Fritz Winter’s engineering objective was to create a reliable method for joining a steel hat with a cast iron friction ring directly during the production process. This composite design significantly reduces vehicle weight, without compromising durability, comfort, or NVH performance. The methodology involves inserting a finished, stamped steel hat (2.5 to 3 mm thick) into the casting mold and then casting the friction ring directly onto it. This process eliminates the need for subsequent machining of the hat. During development, several key challenges were overcome. A patent-pending sealing process was created to prevent liquid iron from spilling onto the steel hat. To ensure a strong bond and prevent the formation of brittle white cast iron, specific measures were applied to the friction ring’s raw shape. Additionally, processes were established to protect the finished steel hat during post-casting fettling and sandblasting. For geometric precision, a patent-pending machining process was developed to properly clamp the disc and align the steel hat with the machined friction ring. The results are highly successful. The new design achieves a weight reduction of 0.9 to 1.2 kg per disc. The innovative sealing method has completely eliminated iron spills. Rigorous chassis dyno tests confirmed that the bond between the steel hat and friction ring exceeded all customer requirements, showing no signs of detachment. The final product meets OEM standards for DTV and run-out, resulting in excellent NVH and brake comfort. Critically, this lightweight concept offers a significant cost advantage over other solutions, with only a small price increase compared to conventional cast iron discs.