Ball screw seals: Types, options, and applications

球螺丝用于各种applications, many of which expose the screw and nut assembly to harmful contamination in the form of dust, chips, or liquids. And like any bearing that uses metal balls (or rollers) on metal raceways, ball screws can experience abrasive wear when exposed to solid contaminants, while liquid contaminants can interfere with proper lubrication — with both conditions reducing the expected life of the assembly and potentially causing catastrophic failure.

One way to protect ball screws from contamination is to completely enclose them in a bellows or telescoping-style enclosure. But the suitability of bellows or telescoping covers should be carefully evaluated, because the negative and positive air pressure caused by their contraction and expansion can act to “suck in” particulates. This air flow can also cause otherwise stationary particles in the environment to become airborne, essentially “stirring up” harmful dust and chips.

In most applications, the best way to protect a ball screw against contamination is by using seals on each end of the ball nut.

制造商使用不同的术语来描述各种球螺钉密封选项，但大多数提供三种基本的密封类型：非接触，全面接触和高性能版本。

Non-contacting ball screw seals

顾名思义，非接触密封件在密封轴和螺杆之间留下很小的缝隙，最常见的设计是塑料labyrinth seals. The lack of contact between the seal and the screw shaft means these designs don’t increase friction and running torque. However, they can allow smaller particulates and liquids to enter the ball nut, so they’re primarily used in environments where contaminants are in the form of larger, solid particles.

Full-contact ball screw seals

有几种形式的密封与球螺钉轴的外径接触。最简单的是刷密封。尽管刷子没有用螺杆提供紧密的，连续的密封件，但它们在擦拭或刷掉较大的污染物方面非常有效，并防止它们进入球螺母。刷子通常与其他类型的全接触密封件结合使用，例如唇部密封或带有预加载的“手指”的分段密封。

Lip seals and segmented seals are both designed to make full contact with the raceway of the screw shaft, providing excellent sealing against both fine particulates, such as ceramic dust, and liquids. Segmented seals typically use a spring mechanism to preload protruding “fingers” against the screw shaft. Lip seals are molded in a profile that matches that of the screw cross-section, ensuring there are no gaps between the seal and the screw shaft.

完整的唇封具有一个内部轮廓，与螺杆的横截面完全匹配。
*Image credit: Bosch Rexroth*

It’s important to note that although full-contact seals offer the best protection against fine particulates and liquids, they do increase friction and drag torque, which should be taken into account when sizing and selecting the motor. This additional friction also causes heat generation, which can affect lubrication.

密封件被认为是球螺钉组件中的维护部分，并且相对易于视觉检查和更换。如果密封材料降解，或者接触型密封的安装变得松动，则更换是一种简单的低成本程序，可以防止螺钉组件的损坏或故障。

High-performance ball screw seals

每个制造商都有自己的“高性能”密封或印章的特殊条件。这些范围从双唇和三重密封到两种或多种密封类型的组合到专门为低摩擦操作设计的完整接触密封。尽管标准的球螺钉密封通常是由Viton（由Chemours制造的一种FKM）制成的，但制造商提供的其他材料（例如EPDM）可以承受高温和低温极端并预防特定化学物质。