Process, Controls & Plant Focus on: Seals, Bearings & Lubrication 22 | Plant & Works Engineering www.pwemag.co.uk April/May 2025 Ball screws are critical in linear motion systems, relying on proper lubrication, alignment, and contamination control—just like bearings in rotary applications. Avoiding common selection, installation, and maintenance mistakes is key to ensuring their efficiency and longevity. James Chanin, Managing Director, Matara UK reports. Avoid common mistakes when selecting ball screws In a linear motion system, a ball screw converts rotational motion into linear movement. Ball screws are both highly efficient and economical devices for motion control, ideally suited to applications where the performance required exceeds those of a lead screw. Ball screws consists of a threaded shaft with a helical path around which ball bearings move; this is the screw element of the unit. The ball assembly behaves as the nut. On first appearance then, ball screws seem relatively straightforward; one of the easiest parts of a linear motion system to specify. But looks can be deceiving! Here we look at the ball screw common mistakes made by customers in relation to ball screws for linear motion applications, from poor product choice, through to incorrect installation and maintenance practices. Product specification Let’s start with the two key ways of manufacturing ball screws: rolled and ground. The former is a lower cost method, resulting in an inexpensive, less accurate product. Grinding, on the other hand, produces a more precise thread with tighter tolerances and lead accuracies, but with a higher price tag to match. Both rolled and ground ball screws will do the job at hand, but if accuracy is key to your application don’t make the mistake of basing your decision on price; choose ground ball screws. The next key decision to be made should be the type of return you want: external, internal or end cap return. This is where things get a little more complicated as there are a number of factors that will determine which is right for you. If you have a high speed and/or high load industrial application, where the process doesn’t generate a lot of dirt, an external return ball screw will generally be a good option. If high load or speed isn’t a factor, but where there is limited space, an internal return ball screw could well be preferable. Lastly, there’s end cap return ball screws which are mostly quieter and cleaner than other designs, so are particularly popular in the pharmaceutical and food industries. Choose wisely. Once you have narrowed down the field by deciding on the type of ball screw that’s right for you, you need to get down to details and select individual ball screws that will work with the load to be carried and at the expected speed. This is frequently where things go wrong as people often miscalculate one or the other. Both speed and load calculations are based on the ball screw diameter, the end fixing and the free screw length. There are
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