Linear ball screws are devices that use a nut that rotates up and down a screw by use of ball bearings that spin in matching helical grooves. The radial motion, or torque, is converted into linear motion called thrust.
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Ballscrews are often combined with linear slides and linear actuators to provide smooth motion in one direction when moving devices, parts or equipment. The threading of the screw and the threading of the nut match one another. Ball bearings roll in the grooves of the threads to provide a rolling friction and precise controllable motion. The screw is made from a strong metal such as steel; the ball bearings are usually made of chrome steel while the nut itself can be either plastic or metal. Linear ball screws offer a number of benefits. When powered by a motor they are up to 90% efficient and consume low levels of energy. Linear ball screws perform critical functions in the manufacturing industry because of the level of control they allow operators to exert while allowing heavy loads to be transported. Ball screw manufacturers can create ball screws that are used in medical equipment, material handling equipment, conveyors and machine tools, robotic lines, precision assembly equipment, miniature instruments, semiconductor manufacturing and fly by wire aircraft and missile control among many other product applications. Numerous industries, including aerospace, computer, electronic, automotive and medical industries utilize ball screws in product applications.
Linear ball screws are generally manufactured in one of three ways. Rolled thread ball screws are cold rolled from a blank and though inexpensive, they are also less precise. Milled threading is the result of machining that uses tools to cut and remove selected material, carving it away. Ground ball screws are the result of a three step process where the steel is machined to its general shape, case hardened then ground on machines with abrasive materials that spin at rapid speeds. Once the screw is manufactured, a corresponding nut is added. The screw and nut do not twist together like a nut and bolt because the balls inside the nut housing make contact with the grooves in the nut and screw threading, spinning inside the nut as the nut rotates up and down the screw. Various deflectors and return methods are used to recirculate the ball bearings because they enable the ball screw to function. In an external ball return system, the balls are returned to the opposite end of the nut by a return tube that curves around the outside diameter of the nut. The internal ball return system employs the same idea but without using exterior tubes. Manufacturers usually identify the diameter of the screw with both metric and standard American measurements. There are certain linear ball screw specifications that are important to consider before installation and usage, including the part's desired lifespan, the temperature and humidity of the operating environment, required torque, output force, backlash, contamination, end machining and end support.
