Custom Ball Screws
Ball screws are devices that convert radial motion into linear motion through an
assembly that uses ball bearings to smoothly slide a nut up and down the threaded shaft. Custom ball screws create the movement necessary to move parts, devices and loads along a single axis and they do so at up to 90% efficiencies when attached to a motor. They are typically made out of a strong metal such as steel or titanium; the nut is infrequently made from plastic. Custom ball screws are used by multiple industries including aerospace, computer, electronic, automotive, medical and especially the manufacturing industry. Because the parts are made to customer specifications, these ball screws can be tailored for use in a variety of applications including medical instruments, material handling equipment, conveyor systems, machine tools,
precision assembly equipment, fly by wire aircraft control and others.
Custom ball screws are composed of two parts: the shaft and the nut. The shaft is threaded along the length of the rod whose diameter varies from fractions of an inch to feet. The
ball screw nut is cylindrical and longer than a traditional nut for a bolt. Its threading matches up with the threading on the shaft. The two parts do not rotate together, however; ball bearings inside the nut's housing travel along the helical grooves. The balls spin and rotate, allowing the nut to remain radially stationary as it moves along the shaft. Because the nut does not rotate, carriages and loads are attached and can be transported this way. The balls are lubricated and, despite the high surface area contact and friction, provide smooth movement. Deflectors and ball return systems circulate the balls inside the housing. Custom ball screws are manufactured through one of three processes.
Rolled ball screws are the least expensive and the least precise. The workpieces are pressed by dies into the desired shape. For custom parts, a custom die would be created and then the ball screws could be quickly produced. The second way, milling, uses tools to machine and cut the workpiece into shape as material is removed mechanically. For
ground ball screws, the workpiece is applied to abrasive materials that are being spun on a machine at rapid speeds, grinding away the excess metal. Ground ball screws are the most dimensionally accurate and precise.
