When determining which types of screws is best for a movement-centric application, an engineer has several options. Often, the decision must be made as to whether a lead screw assembly or a ball screw assembly will work best in the application. While these two types of screws will accomplish the same task, they each have key differences in the way they function and are maintained.
How do ball screws and lead screws work?
The key difference between ball screws and lead screws is the way that the load is carried between each moving surface. The name “ball screw” comes from the recirculating ball bearings within the screw used to reduce friction between the surfaces. Each ball screw assembly features matching helical grooves with its nut that eliminate the sliding friction found in other types of screws.
Lead screws do not use these recirculating ball bearings. This means there is greater contact between the two surfaces, leading to increased sliding friction in the application. For some assemblies, this friction does not negatively impact operation, but in other situations where limiting friction is crucial, this can be a deciding factor between the two types of screws.
Benefits of a Lead Screw Assembly
Lead screws are often viewed as a low-cost alternative to ball screws. Though this low cost does mean less efficient operation, some applications can function effectively with the level of efficiency lead screws provide.
Applications with short cycle times at slow speeds can often function well with a lead screw assembly at a lower cost than ball screws. Though lead screws do often require more up-front testing than ball screws, they can be customized to meet some performance requirements. In addition, they perform better than ball screws in vertical applications and are often used by OEM applications. ACME screws in particular also typically have a higher dynamic capacity than ball screws.
Benefits of a Ball Screw Assembly
Though ball screws have a higher cost, many applications require the high level of efficiency and speed available with these screws. Ball screws are more reliable and predicable, and are therefore replaced less frequently than lead screws. They also have the ability to perform during long cycle times.
A ball screw assembly works best in applications when smooth motion is required, due to its limited friction. They also may be best for assemblies that have strict requirements in other areas, such as speed or weight.
Which screw type is best for you?
Though ball screws and lead screws are used to accomplish the same tasks, they each have areas of strength and weakness that may make them a better fit for one application over another. Having an expert ball screw or lead screw manufacturer that you can rely on to provide recommendations based on your specific application is crucial in finding the screw type that is the best fit for your application.
Still unsure which types of screws are best for your application? The PST team is only a few clicks away. Contact us today.