How to Choose Crossed Roller Bearings

1.Smoothness

A benefit of not recirculating is less frictional resistance fluctuation making high speed ball bearing them extre-mely quiet and smooth. Crossed roller bearings are almost as quiet as cage-limited non-recirculating linear bearing rail using balls 2.Travel limits

The length of travel is limited by the space available for the rails within an application. Since the rails move in opposition to each other, the space required is twice the distance that the load will be carried. An endstop limits travel length. Because there is little or no difference between static and dynamic frictional resistances – even under low-load conditions – crossed roller bearings are well suited for minute motion.

3.Wear

For motion control applications with extremely fast acceleration and deceleration (at dimensions ranging from 20-500 mm lengths, 3-14 mm rollers) endurance can be 160 million cycles. This affect often occurs as a result of high acceleration and uneven preloading or load distribution, as well as orientation (inclined or vertical) can easily cause creep.

4.Travel length

The longer the travel the longer the rail has to be. However, as opposed to recirculating-ball bushings, which require a shaft only as long as the travel distance, with crossed roller bearings, the whole rail assembly must be twice as long as the stroke. That’s because both rails containing crossed roller bearings move in opposite directions. So the whole assembly has to move within a space that is twice as long as the travel length.

 

5.Accuracy and deflection

Crossed rollers provide a large contact area, which reduces elastic deformation. Because of this greater stiffness, crossed rollers provide consistently precise movement.

The crossed roller is less forgiving of mounting surface inaccuracies because of the linear bearing’s rigidity and the way they are designed.  Often the bearings can be specified with mounting tables hone to exacting standards. This makes sense since for ultra precision, 2 microns is the maximum allowable deflection from the mounting surface.

6.Fit and interchangeability

The cage in any bearing prevents ball-to-ball or roller-to-roller contact, which can cause more friction and wear. Whether the cage holding crossed roller bearings are metal, resin or other material, it alters, somewhat, a crossed roller bearing’s dimensions, which affects how they fit into a design. Stoppers can also affect their size and therefore their fit.

Resin, as opposed to metal cages, allow the crossed rollers to be much closer together allowing the total number of rollers to be greater in the same space.In addition to stoppers and the cage material and design, another factor that affects interchangeability is the design of the anti-creep mechanism. External anti-creep mechanisms often obviate interchangeability. Internal mechanisms are much more accommodating.

7.Cage

In non-recirculating linear components, the retainer floats between the rails and can drift (or creep) from center position.With higher preload, it is even more difficult and damaging to skid the cage back in place. Cage creep is damaging because every time it creeps, rolling ele-ments are not rolling, instead they are slipping and causing metal to metal rubbing, which will wear out elements very quickly.