What Is a Ball Screw?
A ball screw is a mechanical component consisting of a screw shaft with a helical groove (or peak), a screw nut, and a ball.
It represents a mechanism for converting linear motion to rotational motion, or vice versa, and rotational motion to linear motion. The rolling motion of the ball screw between the threaded screw shaft (shaft) and the screw nut results in a highly efficient feed screw.
In this case, “screw” does not mean a screw for fastening parts, but a different way of using the threaded part.
Uses of Ball Screws
Ball screws are used in a variety of applications, including machine tools, semiconductor manufacturing machinery, and industrial robots.
For example, ball screws are used in numerically controlled machine tools called NC (numerically controlled machining) to configure the feed mechanism and obtain precision positioning accuracy. Ball screws have also long been used in steering gears that move the front wheels by the steering wheel of automobiles. Today, ball screws are also used in machines in various fields such as food equipment, medical equipment, and printing equipment, as well as for vehicles such as automobiles, trains, and airplanes.
Principle of Ball Screws
In a ball screw, a screw shaft (shaft) with screw-shaped grooves (or mountains) is called a ball screw, and when it is rotated, a ball engages the screw and the screw nut containing the ball moves left to right (or up and down). The screw nut is attached to the part or component to be moved to obtain the required motion.
A ball screw is a mechanical component that receives only an axial load and converts rotational motion into linear motion. The ball screw causes the required component to move linearly in the axial direction, and the axial load is applied to the screw shaft via the screw nut. Other loads (vertical loads, moment loads, etc.) must be supported by the guide rail.
Therefore, a linear motion mechanism that includes a ball screw consists of a ball screw + guide rail + power source (motor).
The ball screw uses tribology (friction control technology) in which a ball is placed between the screw shaft and the screw nut to allow it to roll lightly. Because the balls must circulate infinitely, a circulation component is essential in addition to the screw shaft, screw nut, and balls. Circulation methods include the following:
- Return tube type
- End deflector type
- End cap type
- Return plate type
Uses are divided according to size and precision, with small-diameter sizes mainly used in the precision field, and larger sizes mainly used in machine tools and conveying machinery.