Application: Ball Joint Assembly
Problem: A customer had a ball joint assembly design that required stacking the components into a housing and roll forming the outer lip over the edge of a flat cover plate to seal the parts inside the housing. The housings were made of a high strength steel that was hardened to resist wear. The outer lip was heat treated so that it would be strong, but formable. The combination of a hard surface and ductile core was impossible to repeat from one heat treat batch to another. If the outer lip was too hard, the spin edge would crack giving a snake skin appearance. If the outer lip was too soft, the spin edge would form perfectly, but the strength would be insufficient to contain the components under rated stresses. The ball joint would come apart prematurely.
The MWI Solution:
- Met with the customer to design a press in cover plate.
- When the components are assembled into the joint, the cover plate sits above on a circular ledge.
- Re-designed the ball joint housing to have an internal cut ring.
- When force is applied to the top of the cover plate the outside diameter expands to fill the internal cut ring as the cover plate flattens.
- Force is applied until the cover plate is flat, the outside diameter of the cover plate seals against the inside diameter of the internal cut ring to prevent grease leakage, and the proper articulating stud force is achieved.
The ball joint housing can be heat treated to achieve the necessary strength because there is no spin edge to crack. This ball joint is now the strongest joint available in the customer’s product line.