Ball Screws:
A ball screw is a mechanical device for transforming rotational motion to linear motion. On a ballscrew, a threaded shaft provides a spiral raceway for ball bearings, which act as a precision screw. Ballscrews apply or withstand high thrust loads with minimal internal friction. They are made to close tolerances and are therefore suitable for use in situations in which high precision is necessary. Ballscrews consist of the ball assembly, which acts as the nut while the threaded shaft serves as the screw.
Ballscrews are found on machine tools, robots and precision assembly equipment. While reducing friction, ball screws can operate with some preload, effectively eliminating backlash. This feature is essential when they are used in computer-controlled motion-control systems such as machine tools and high precision motion applications. Ballscrews are considerably more expensive than acme screws. The low friction in ball screws yields a much higher mechanical efficiency compared to alternative linear motion products. A typical ball screw may be 90 percent efficient, versus 50 percent efficiency of an acme screw of equal size. The higher cost of a ball screws is often offset by the lower power requirements.
There are two types of ball screws, rolled shaft and high precision. Rolled ball screws are fabricated by rolling, yielding a less precise, less costly but still mechanically efficient product. Rolled ball screws have a positional precision of several thousandths of an inch per foot.High-precision ball screws are typically precise to one thousandth of an inch per foot or better. These ball screws are machined, case hardened and then ground.
Manufacturers:
- NSK
- Thomson (Danaher Motion)
- Nook
- RBC
- Star
- NTN
- Rockford
- SKF
- Nachi
- INA (Schaeffler)
- THK
- IKO
- Koyo
- Schneeberger
- Duff Norton
- Joyce Dayton
