Ball & Lead Screws

Many factors must be considered when designing or selecting a linear positioning device. Operating load, speed, accuracy, environment, and power requirements all play major roles in the design decision. Whether the engineer selects a rolled ball screw, precision ground ball screw, or an Acme lead screw, the lubricant should also be carefully considered. A properly selected lubricant minimizes friction, reduces torque, increases the screw’s efficiency, and extends performance life.

Enhancing grease performance.

High quality synthetic greases offer many performance advantages over mineral-based lubricants. Synthetic lubricants function over wider temperature ranges; they offer greater thermooxidative stability and lower volatility; and they retain the viscosity needed to provide an adequate film thickness through a specified range of operating temperatures, speeds and loads. Special additive packages can further improve a grease’s natural ability to resist water wash-out and reduce wear in the presence of shockloading and vibration. Other additives can improve lubricity, to further reduce friction.

Specifying a lubricant.

Proper lubrication plays an especially vital role in the performance and life of Acme lead screws with bronze or polymer nuts, because they are subject to higher friction and greater wear than ball screws. Even with self-lubricated nuts, lead screw performance can be significantly enhanced with light greases. Additional lubrication can also reduce heat in these units. Polymer or plastic nuts benefit from silicone-based greases and PTFE additives, which lower friction, increase efficiency and prolong performance life. Solid lubricants such as PTFE may also improve the roughness associated with the increased preloads of anti-backlash nuts.

Precision ground ball screws, where precise motion and smooth, quiet operation are desired, can take advantage of ultrafiltration technology. Pioneered by Nye Lubricants, ultrafiltration of grease and oil results in lubricants with unsurpassed cleanliness. For greases, ultrafiltration also improves the homogeneity of the thickening agent.

Ultrafiltration.

Ultrafiltration removes virtually all particulate matter from grease and oil. For greases, it also improves the homogeneity of the thickening agent. Nye will ultrafilter any oil or grease and typically will recommend this service for precision bearing and ball screw applications to extend the bearing life.