Metric ball screws are devices that convert the torque of a threaded nut on a threaded screw into thrust using ball bearings to provide smooth motion. The diameters of these devices are typically identified in both metric and American standard measurements for ease of use worldwide.
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Metric ball screws are frequently used in combination with linear actuators and slides to provide the necessary movement for transporting devices, parts and equipment in a single straight line. The threading of the nut and the threading of the screw are complementary. Small balls made of chrome steel spin in the helical grooves between the screw and nut, providing rolling friction and smooth, precise movement. The assembly is made from strong metal; steel is most commonly used, though the nut can be constructed from plastic. Metric ball screws use motor power very efficiently, reaching levels of 90% efficiency while consuming little energy. Many industries benefit from metric ball screws, especially the manufacturing sector. Metric ball screws are widely used in automated assembly lines, material handling equipment, conveyors, machine tools, fly by wire control, precision assembly equipment and more. They are also used by many industries for the precise control they offer including the aerospace, computer, electronic, automotive and medical industries.
Metric ball screws can be manufactured using a variety of techniques. Common processes include conventional rolling, milling and grinding. There are three main ways that the threads on metric ball screws are fabricated: through rolling, milling and grinding. Metric rolled ball screws are cold rolled from a blank and are inexpensive but less precise, though still mechanically efficient. Milled threading is the result of machining that uses tools to cut and remove selected material, carving it away. Ground threads are the result of a three stop process. First, the steel is machined to its gross shape. It is then case hardened and ground on machines with abrasive materials that spin at rapid speeds. This process allows the resulting metric ground ball screws to withstand high temperatures that would otherwise distort the shape and efficiency of the screw. The nuts are fabricated in a similar fashion. There are a few variations of metric ball screws available for use in industrial settings. Ball screw manufacturers commonly produce acme screws, lead screws and ground metric ball screws, each differing in size and output. Lead screws use lubrication and fine machining between the screw and nut to slide instead of using actual rollers to create movement. They are placed in the same category as ball screws because of their similar function and capacities. Lead screws can accommodate high shock loads. Acme screws are the most widely used lead screw and are often used in applications that require high accuracy while at low speeds.
