X-Y positioning stages are found in machines for assembling precision products, such as disk drives, lenses and fiber optic components. They are used for applications in which accuracy and repeatability are more important than speed. They are also used in less precise applications, when it’s necessary to support high inertia loads.
Among the first options to consider when specifying a positioning stage is the base, which must be flat and stable. The base can be made from aluminum, steel, ceramic or granite. Aluminum has a good stiffness-to-weight ratio. Though aluminum has a high coefficient of thermal expansion, it also conducts heat very well, making it a good choice for applications with rapid temperature changes. Steel is much stiffer than aluminum, and its thermal expansion is half that of aluminum. However, it’s also more expensive. Polished granite is among the flattest surfaces available, so it’s ideal for use with air bearings. It’s extremely hard, nonmagnetic and nonreactive. But, it’s also very heavy.