It is sheetmetal and it was the only realistic way to create the cage. It is actually a very simple quilt form feature.
This should probably be reserved for a different discussion, however.
edit: I have submitted the bearing cage as a support case. This is a nearly perfect test case for both sheetmetal forms and patterns. In this case, one instance of the pattern fails, yet I can make the exact same form feature from the patterned form quilt at the failed location. FYI, the form can be a semi-sphere or a full sphere. The rounds on the edges are part of the form feature.