White Paper: Packaging & Sterilization
Quality, American Made Miniature Ball Screws from PBC Linear
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PBC Linear miniature ball screw assemblies are USA made at their Illinois headquarters, allowing for quick shipping and integration into your linear motion applications. Our head of Engineering gives a quick overview on how ball screws work and when to choose between a ball screw and a lead screw. Ball screws are available in 6 mm, 8 mm, and 10 mm diameters with various leads and quality grades of 5, 7, and 10.
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Overview
The document provides an overview of ball screws, a mechanical assembly that converts rotary motion into linear motion using a screw, nut, and ball bearings. The ball bearings roll within the threads of the screw and nut, resulting in low rolling friction, which enhances the efficiency of ball screws compared to lead screws, which rely on sliding friction. This efficiency allows ball screws to require lower torque to move the same load, have higher load ratings, and offer more precise positioning due to controlled clearances between the threads and ball bearings.
Ball screws are typically made from hardened steel, which contributes to their durability and load capacity. In contrast, lead screws are often made from softer materials, such as polymers or bronze, which limits their performance. Additionally, ball screws can operate at higher rotational speeds without generating excessive heat, a common issue with lead screws due to friction.
The document also addresses the concept of backlash in ball screws, defined as the free axial movement of the nut when the screw is stationary. Backlash can be minimized by using larger diameter bearing balls or double-nut designs, with standard backlash being ≤ 0.050 mm and reduced backlash being ≤ 0.013 mm.
Another important topic covered is the phenomenon of "back driving," which occurs when an actuator's carriage moves due to an external force overcoming the drive train's resistance. This is particularly relevant in vertical applications where weight loads can cause the carriage to drop when power is removed. To prevent back driving, designers may opt for low-efficiency drive systems or incorporate brakes into the drive train.
Regarding installation, the document notes that ball screws may come with only a rust inhibitor applied, which is insufficient as a lubricant. Therefore, they should be cleaned and properly lubricated before use.
PBC Linear's ball screw assemblies are manufactured in the Midwest, ensuring quick shipping and integration into various applications. The company offers a range of screw diameters (6 mm, 8 mm, and 10 mm) and leads, along with high-quality test stands for accuracy verification. Overall, the document highlights the advantages, functionality, and considerations of using ball screws in linear motion applications.