As the saying goes, you can never be too rich or too thin.
When engineers at ASML (Tempe, AZ), a semiconductor equipment manufacturer, designed their newest lithography tool, they needed an extremely thin, yet stiff pivot assembly to move a framing blade for the light beam. "A lithographic tool is like a slide projector," says Serge Wetzels, an engineer at ASML, "where the light beam must be framed to hold a certain shape."
To achieve the desired stiffness, the pivot had to incorporate two preloaded ball bearings yet still be thin enough to fit into an already compact piece of machinery and handle a decent load.
ASML chose the new B4-72 bearing from Dynaroll. This high precision ball bearing is a mere 0.031 inches tall. "It has a very low profile," says Wetzel, "which was crucial in this application because there was very little space to work with. It also has a large diameter, so it can hold a large shaft. That combination is pretty unique."
In order to get any stiffness in an assembly, two bearings are typically required, and they have to be preloaded to take out the inherent axial play. "With the B4-72 bearing, you can put a pair in a preloaded assembly where the total width is about 0.0625 inch," says Simon Harrison, president of Dynaroll.