A ball screw is a precision mechanical transmission device that converts rotary motion into linear motion or vice versa. Its core principle lies in the substitution of rolling friction for traditional sliding friction, thereby achieving high efficiency, high precision, and long service life in transmission performance. The following is an introduction to the working principle and structure of a ball screw.

I. Basic Structure of a Ball Screw

A ball screw mainly consists of a screw shaft, nut, balls, recirculating device, and sealing device, etc.

1. Screw Shaft

A threaded shaft with a helical raceway groove on its surface, usually made of alloy steel or carbon steel, and processed through heat treatment and grinding to ensure hardness and precision.

The interior is equipped with raceway grooves that match the lead screw, and the balls circulate within them. The nut structure is divided into two types: internal circulation and external circulation. The former achieves the circulation of the balls within the nut through a reverse device, while the latter guides the balls through an external conduit.

3. Balls

High-precision steel balls, as rolling elements, transfer loads between the raceways of lead screws and nuts. Their diameter tolerances are usually controlled at the micrometer level, and the material must have high hardness and wear resistance.

4. Circulation System

Ensure that the balls form a closed loop during movement to avoid jamming. The inner circulation structure is compact, while the outer circulation is more suitable for high-speed scenarios.

II. Working Principle of Ball Screws

When one of the screw or nut rotates, the balls are forced to roll in the raceways, pushing the other component to move linearly. The mechanical process can be divided into the following steps:

1. Force Transmission Path

The rotational torque is converted into axial thrust at the contact points between the balls and the raceways. Due to the rolling friction coefficient being much lower than the sliding friction, the mechanical efficiency can reach over 90%.

2. Motion Trajectory

The balls roll along a helical path within the raceway and are forced to return to the starting end through a recirculator, forming a continuous loop. For instance, a single nut structure typically contains 3 to 5 turns of balls and achieves "self-recirculation" through a reverse device.

3. Preload eliminates clearance

Axial clearance can be eliminated and rigidity improved by pre-tightening with double nuts or increasing the diameter of the balls. The preload force must be accurately calculated; too much will increase frictional resistance, while too little will fail to suppress reverse backlash. This is an introduction to the working principle of ball screws. The technical principle of ball screws integrates precision mechanical design, materials science, and tribology theory. Friends who need ball screws can click on the lower right corner of the website to get online guidance from professional engineers for selection.