O óleo é adequado para lubrificar fusos de esferas?

Is the oil suitable for lubricating ball screws?

ball screws

The short answer is yes: ball screws can be lubricated with grease or oil. Grease is most commonly used for ball screw lubrication because it does not involve complicated delivery methods and requires less frequent relubrication intervals. But despite the simplicity of using grease, in many applications oil lubrication is the best choice for ball screw assemblies.

First, the oil provides cooling and minimizes heat build-up inside the ball screw assembly. Heat causes thermal expansion of the screw shaft, which changes the size of the screw threads and negatively affects positioning accuracy, so reducing heat can be critical in applications requiring high speed and/or accuracy. And if the oil is circulated through an external lubrication system, the cooling effect of the oil can be significant. Circulation systems also filter oil residues, extending lubrication life and reducing wear on the screw assembly. The disadvantage is that an external circulation system adds complexity and cost to the assembly.

When using oil for ball screw lubrication, it is important to use the right viscosity in the right quantity. If the viscosity of the oil is too high or there is too much oil, excessive heat may be generated. On the other hand, if the viscosity of the oil is too low or if there is not enough oil lubrication, the screw will experience additional friction and wear will be accelerated. The correct oil viscosity is based on the screw's average speed, diameter, and operating temperature. If the applied load is high, typically greater than 15-20% of the dynamic load capacity, manufacturers often recommend using oil with extreme pressure (EP) additives for additional wear protection.

ball screw lubrication

Manufacturers often provide selection guides to help choose the proper viscosity of oil for ball screw lubrication, based on operating temperature and average screw speed.
Image credit: Thomson Industries, Inc.

With oil lubrication, it is also essential that the application conditions are sufficient to allow the formation of an elastohydrodynamic (EHD) lubricating film. This film separates the ball holders from the tracks and prevents metal-to-metal contact.

ball screw lubrication

An oil of the right viscosity and in the right quantity will allow a ball screw to operate in the region of elastohydrodynamic friction.
Image credit: Anton Paar GmbH

There are three main conditions that determine whether a lubricant film will develop: the viscosity of the lubricant, the screw speed, and the pressure between the balls and the raceway. Due to the influence of speed on EHD lubrication, low-speed applications often require grease, which provides better protection under conditions of boundary lubrication (essentially metal-to-metal contact) or mixed lubrication (a combination of metal-to-metal contact and backing lubrication). .

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