An Introduction to Ballscrews

Linear ballscrews are widely used as a form of motion control in a linear motion system, enabling linear movement rather than rotational movement. They are ideal for applications that require high levels of precision and control and can be found in applications ranging from machine tools to flight controls in aerospace, robotics, and precision engineering. 

Join Matara as we discuss what a ballscrew is and the many types of ballscrews on offer, fit for your application.

What is a ballscrew and how does it work?

A ballscrew is a mechanical device – a linear actuator – that converts rotational motion to linear motion. A threaded shaft provides a helical path for ball bearings, allowing them to behave like a screw; the ball assembly acts as the nut while the threaded shaft is the screw. The balls roll between the nut and the screw in the grooves when either the screw or the nut rotates, providing linear movement in the form of a screw actuator.

Why choose a ballscrew for linear motion?

Ballscrew actuators produce minimal friction and are generally built to much higher tolerances than standard acme or lead screws. This makes them well-suited to high-precision applications with a high payload. A linear ballscrew tends to provide the following benefits:

• Smooth movement
• Accuracy of movement and position
• Precision control
• Efficient output; smaller motors are needed thanks to lower levels of torque being required
• Continuous, high-speed movement
• Lower friction leading to cooler temperatures

Disadvantages of ballscrews

Ballscrews tend to be rather bulky because they need a mechanism to recirculate the balls. They also require braking systems to prevent back driving, which isn’t generally a problem with lead screws, their closest alternative. Ballscrews require some maintenance in that they need to be lubricated regularly and are noisy in comparison to lead screws.

What are the main types of ballscrew?

The main areas in which ball screw actuators vary, other than the apparent size and load capacity options, are in relation to the method used for the return of the balls back to the top of the nut for recirculation:

Internal Return

The contained ball return allows the balls to exit the track and directs them into the following thread, returning the ball. It keeps the overall size smaller and provides higher accuracy. This option is less robust than the external return models and unsuitable for high-load or high-speed applications. They tend to be used in delicate or high-precision applications.

External Return

The ball return is external to the nut, usually by means of a tube. This results in a larger footprint but allows it to be much better at dealing with heavy loads. Cleanliness and internal lubrication can be an issue for these types of ballscrews. They are used in high-speed and/or high-load industrial applications such as process automation or CNC machining.

End Cap Return

An end cap deflects the balls through a route bored transversely down the nut body, where the cap at the other end deflects the balls back into the threads. This type of ballscrew is generally quieter and cleaner than the other options and is, therefore, often used in food preparation and medical applications.

Ballscrews can also be categorised by how they are manufactured; rolled ballscrew threads are produced in a single process, which is the more cost-effective production method. Ground ballscrew threads are made using machining centres to carve out the threads from material blanks and are then ground to produce a precision finish. Rolled ballscrews are generally less expensive and tend to have rougher finishes than ground ballscrews, which provide a much tighter precision tolerance and are more accurate and efficient.

See how Matara ballscrews can aid your application

Matara offers all types of ballscrews suitable for a wide variety of applications. If you are interested in one of our ballscrews or need help finding the right ballscrew for your application, be sure to contact us, and a member of our team will be happy to help. 

To learn more about ballscrews and what we do at Matara, check out our technical guides and case studies for all you need to know.