The Source of Precision Power—— The Core Role of Ball Screws in Arm Robots

Robotic arms are playing an increasingly important role in industrial automation, medical surgery, and even space exploration. They can perform complex tasks such as welding, painting, handling, precision assembly, and even minimally invasive surgery. While we marvel at the precision, high speed, and heavy-load capacity of robotic arms, a key component plays a crucial role: the ball screw. It converts rotary motion into precise linear motion.

A ball screw is a mechanical transmission element primarily composed of a lead screw, nut, balls, and an inverter.

Lead screw: A shaft with a precise helical groove.

Nut: A component with matching helical grooves inside that mates with the lead screw.

Balls: Interposed between the helical grooves of the lead screw and nut, they act as an intermediary.

How it works: When a servo motor drives the lead screw, the balls circulate within the grooves, pushing the nut for precise linear motion along the lead screw axis. This "rolling friction" is the source of its high performance.

Ball screws offer irreplaceable advantages in the design of robot joints (especially linear joints) and end effectors:

1. High Precision and Positioning Accuracy

Ball screws are manufactured with extremely precise technology, resulting in extremely low lead errors. This means that a specific rotation of the motor produces an extremely precise linear displacement of the nut. This is crucial for robots that must repeatedly reach the same position for tasks such as chip picking and precision dispensing.

2. High Efficiency

Due to their rolling friction design, ball screws can achieve transmission efficiencies exceeding 90%.

More Energy Efficient: Less energy is wasted as heat during transmission.

Easier Control: High efficiency means lower backlash and improved reversibility, resulting in faster system response and more precise control.

3. High Rigidity and Load Capacity

The point contact between the ball and the groove allows them to withstand significant axial loads. This allows robot arms using ball screws to lift heavier workpieces or maintain extreme stability during tasks such as milling and grinding, resisting machining reaction forces and preventing vibration and deflection.

4. Long Life and High Reliability

Rolling friction causes much less wear than sliding friction. With proper selection, lubrication, and maintenance, ball screws offer an exceptionally long service life, ensuring industrial robots can meet the demanding demands of 24/7 continuous production while reducing maintenance costs and downtime.

Ball screws are already widely used in arm robots, such as:

Industrial robot joint actuation, end effectors for high-grip grasping, and SCARA robots for Z-axis lifting, widely used in assembly and handling.

Despite their significant advantages, ball screw applications also face certain challenges:

Cost: Manufacturing costs are higher than those of ordinary sliding screws.

Noise: Some noise is still generated even at high speeds.

Maintenance: Regular lubrication is required, and they are sensitive to dust and debris, typically requiring protective covers.

As robotics advance towards higher speeds, higher precision, and greater intelligence, ball screw technology will continue to innovate.