How to choose a suitable lubrication for linear guide and ball screw?

For recirculating linear bearings,such as profiled guides and ball screws,lubrication separates the bearing(ball or roller)from the raceway,minimizing friction and wear,dissipating heat and preventing corrosion.It also promotes smooth operation of seals and reduces seal wear,ensuring their effectiveness in keeping bearing lubricants in and preventing contamination.

Lubricant failure can lead to excessive wear,overheating and bearing failure.

The formation of the lubrication film depends on the viscosity of the lubricant,the speed of the bearing and the pressure between the bearing and the raceway.For profiled guide rails and ball screws,grease or oil can be used for lubrication.The choice depends on application parameters including:temperature,load,vibration,speed,environment,pollution,and stroke length.

●Grease

For most linear guides and drive applications,grease is the better lubrication choice.It adheres to bearing surfaces better than oil,lasts longer,and is less likely to fall off or pop out of rotating parts.

Grease lubricants consist of three main components:base oil,thickener,and additive(usually rust inhibitor).When choosing a grease lubricant,the viscosity of the base oil determines how the lubrication film separating the rolling elements from the raceway develops.

Linear systems typically use lithium-based greases that do not contain solid additives such as MoS2(molybdenum disulfide)or PTFE(Teflon)and have a consistency class between 0 and 3.These greases perform well in high-load applications and have good antioxidant stability.

●Oil

Oil lubrication is recommended for high-speed applications because it dissipates heat more easily than grease.It also flows and disperses better than grease.But when using oil lubrication,the direction of the bearing and the position of the lubrication port must be considered.When components are mounted side-on or vertically,oil lubrication does not flow to bearings and raceways above the lubrication port.

Using oil lubrication,the direction of the parts must be considered.

Some machine manufacturers use atomizing systems for oil lubrication.While these systems can be more complex and expensive than manual or even automatic grease lubrication systems,oil mist systems offer the added benefit of generating positive pressure inside the bearing.This helps prevent contaminants from entering the bearing and further assists in cooling.

It is important to note that incompatibility between lubricants can cause the lubricating ingredients to separate and render them ineffective.Some manufacturers offer pre-lubricated linear guides and ball screws that are ready to be installed and used,while others simply apply preservative grease or oil. To ensure compatibility between the initial lubricant and the in-service lubricant,check the manufacturer's lubrication specifications.If the two are not compatible,the component should be wiped and blown before any additional lubrication is applied.

Regardless of the type of lubrication(grease or oil),maintaining the appropriate amount of lubrication is critical to achieving optimal bearing life.Manufacturers of linear guides and ball screws publish recommended lubrication amounts and intervals,which depend on the type of lubrication used and the speed and temperature of the application.Other factors such as shock loads,vibration and pollution can also affect the life and performance of lubricants.For applications with these conditions,lubricant manufacturers can analyze operating parameters and recommend lubricants that ensure optimal bearing life.

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