|Linear Crossed Roller Bearings (CRB's)|
Crossed roller bearings inherently have more load capacity than ball slides because of the line contact between each roller and the raceway, as illustrated in the following figure.
However, ball slides still have the advantage of being self-cleaning, so that crossed roller bearings (CRB's) need to be carefully isolated from dust and debris. Debris which settles on the raceways or rollers is compacted by the roller instead of being driven away from the interface, and damage to the roller and raceway surface results. Protection of CRB moving parts is often accomplished through accordion-type shields that envelope the slide.
Regarding the mechanical construction of a crossed roller slide rail, rollers are alternately turned ninety degrees and are canted so that loads from all directions can be supported. CRB's can be thought of as the linear analog of tapered rotary roller bearings.
|Low Profile Linear Crossed Roller Bearings|
In a low profile design of CRB, as illustrated in the next figure, the rail raceways are integrated to the body of the carriage and base. This design is compact, especially in height. It is also strong because of the solid nature of the raceways.
Crossed Roller Bearing Slide (low profile design)
However, this type of CRB costs more than the modular kind discussed in the next section. It also tends to be heavier than a modular design since all of the carriage or base needs to a single monolithic piece of hardened steel.
|Modular Linear Crossed Roller Bearings|
The modular CRB is lighter than the low-profile design since most of the carriage and base can be made from aluminum. The raceway inserts are made from hardened steel rods which are cut in half and ground. Since as with linear ball slides the steel rods are a mechanical commodity, modular CRB's are considerably less costly than equivalent low-profile designs. However, modular CRB's suffer from a larger form factor because of all of the assembled parts and the fact that aluminum is not as rigid and strong as steel.
Crossed Roller Bearing Slide (modular rod raceway design)