Automatic or Manual Grease Lubrication
Re-lubrication of ball screws should be done with grease having the same, or compatible, thickener as the grease used for factory lubrication. The base oil viscosity should also be approximately the same. If not specified otherwise, Steinmeyer uses Kluber Staburags NBU 8 EP for factory grease fill of the nut. Please note that the factory grease fill is only enough for initial operation, until the first required re-lubrication.
Ball screws with regular plastic wipers should be re-greased every 500 hours of continuous operation, or four times a year. Ball screws with felt wipers have a recommended re-greasing interval of 1000 hours of operation, or twice a year.
If the ball screw is fitted with felt or combination wipers and is adequately protected from dirt and liquids (e.g. water, coolant), then the re-lubrication interval may be extended to 2000 hours or once a year. In such cases, Steinmeyer will pack the ball nut with long-term grease Kluber Isoflex NBU 15, and impregnate the felt wiper with an oil compatible with this grease. Please consult with our application engineers if you want your ball screw prepared for long-term lubrication.
Automatic Grease Lubrication
There are two possible ways to automatically re-lubricate ball screws. Either the nut is connected to an automatic lubrication pump with multiple ports, or a lubrication cartridge is used. Both require a grease which is not too viscous and can be reliably pumped through piping to its destination. Grease cartridges powered by chemical gas generators keep the grease pressurized all the time, which can cause the base oil to separate from the thickener resulting in clogged lines and lubrication breakdown. We recommend electromechanical cartridges, which use a gear motor and a lead screw to pump the lubricant. These do not keep the grease under continuous pressure, thus preventing such problems.
Normally, liquid greases NLGI class 0 or 00 are used for automatic grease lubrication, because they can be pumped through long lines more easily. With large enough pipe diameters, grease class 1 or even 2 can be used as well - but should first be tested.
Mineral oil based lubricants degrade with time in two ways:
- They are attacked by aggressive chemicals (for example oxygen) from their environment, which causes a polymerization of the hydrocarbon or oxidation. The lubricant turns into a solid with time, but the process is slow in a normal environment, so re-lubrication in normal intervals replaces the lubricant before it becomes too degraded. However, this chemical aging limits the storage period of pre-greased components to 2 - 5 years. Specifics can be obtained from grease manufacturers.
- During use, the hydrocarbon molecules are subjected to mechanical stresses when they are passed through the contact patches. This mechanical stress causes the molecule chains to break up over time, reducing the viscosity. The maximum usage time of the lubricant can be calculated - please contact us.