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What Are the Pros and Cons of Using Ball Screws?

  • February 1, 2019

Originally known as an antifriction nut, a ball screw is a mechanical device that’s used to convert rotational motion into linear motion. They feature a long threaded shaft with ball bearings to withstand significant stress and weight, all while minimizing friction. A typical ball screw, as shown to the left, has both a screw and a nut. There are helical indentions formed on the outside of both the screw and nut, allowing ball bearings to roll between them. When the ball screw rotates, the ball bearings travel to the return system before changing direction.

The ball screw was invented by Rudolph G. Boehm in the late 1920s. Today, they are used in countless manufacturing applications, some of which include airplanes, missiles, automobiles, 3D printers and machines. If you’re thinking about using ball screws in your company’s manufacturing applications, though, you should consider the pros and cons.

Ball Screws vs Lead Screws: What’s the Difference?

Ball screws look like lead screws, but only the former has ball bearings inside the nut. In lead screws, the nut doesn’t contain ball bearings, nor does it actively roll. Ball screws, on the other hand, contain a nut in which ball bearings circulate to support the load and reduce friction.

Ball Screw Pros

Ball screws offer a high level of mechanical efficiency. Statistics show that ball screws are about 90% efficient, meaning they are able to convert nine-tenths of the application’s rotational motion into linear motion. In comparison, lead screws have an average mechanical efficiency of just 20% to 25%. Based on these numbers, it’s safe to say that ball screws are between three and four times more efficient as converting mechanical energy than lead screws.

Of course, ball screws also produce minimal friction. This is because they are designed with a nut in which ball bearings circulate. The ball bearings create a smooth gliding surface for the screw, thereby reducing friction and subsequently increasing the ball screw’s lifespan.

Ball Screw Cons

The only real disadvantage to using ball screws is their susceptibility to be back-driven. Since they create such little friction, they can be back-driven at certain lead angles.

Other than the possibility of being back-driven, ball screws cost slightly more than similar mechanical devices, including lead screws. For manufacturing companies on a tight budget, the higher cost may deter them from choosing ball screws. But considering the superior mechanical efficiency and low internal friction, ball screws will remain a popular choice for manufacturers looking to improve the quality and performance of their products.

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