Influences of oil additives on the wear behavior of ball screws

Abstract

The lubrication in a tribosystem has a significant influence on the resulting friction and wear behavior. The spectrum of the used base oils for lubrication preparation increases continuously. That affects especially the use of environmentally friendly substances in order to save the environment. Regardless of the chemical origin, the lubrication systems should primarily take over the function of positive influencing of the friction and wear behavior. The ball screw as a central component of the machine tool feed axis transforms the rotational motions of the servo motor to a linear motion of the slide and takes over the fine positioning function in machine tools. According to the roller bearing lubrication specifications a grease or oil lubrication for ball screws is indispensable. The lifetime calculation is based on an elastohydrodynamic lubrication film. Within the research activities of the collaborative research center (CRC 442) ball screws with additived oils and nonadditived synthetic ester, which are developed within the collaborative research center, are tested on the test stand. The aim is to clarify the question, which influence the oil additives have on the wear behavior and preload loss in ball screws for machine tool applications. Investigations have clarified that oil additives have a significant influence on the preloading of the ball screws which are operated in the mixed friction area. The investigations of the axial rigidity as well as the investigations of the no-load torques clearly showed that oil additives cause a lower preload loss in ball screws compared to nonadditived oils.