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LYMC Precision Crossed Roller Bearing

Crossed Roller Bearing

A crossed roller bearing is a special type of bearing with a split inner ring and a rotating outer ring. Since the divided inner ring or outer ring is installed with the roller and spacer, it is fixed with the cross roller ring to prevent separation from each other, so it is easy to install the cross roller ring.

Since the rollers are arranged in a cross, only one set of Cross Roller Rings can withstand loads in all directions, and the rigidity is 3 to 4 times higher than that of conventional models.

At the same time, since the inner ring or outer ring of the crossed roller bearing is divided into two structures, the bearing clearance can be adjusted, and even if a preload is applied, high-precision rotational motion can be obtained. Moreover, due to its special structure, it is usually used as a joint bearing in industrial robots.

1.product description

Their rollers are arranged at right angles to each other at intervals between the inner and outer wheels. They can bear loads from all directions at the same time (such as axial, thrust or momentum loads, etc.).

Because the rollers are in linear contact with the track surface, the possibility of elastic deformation of the bearing under load is very small.

This type of bearing is widely used in such occasions as industrial automatic robots, working machinery and medical facilities, etc., where high rigidity, tightness and high speed are required to ensure accuracy.

In a crossed roller bearing, since the cylindrical rollers are arranged perpendicular to each other through spacers, a single crossed roller bearing can withstand loads in all directions, including radial load, axial load, and moment load.

The size of the inner and outer rings is minimized, especially the ultra-thin type is a small size close to the limit, and has high rigidity, so it is most suitable for the joint part or rotating part of industrial robots, the rotary table of machining center.

It is used for robot rotating parts, precision rotary tables, medical equipment, measuring instruments, IC manufacturing equipment, etc.

crossed roller bearing Alt.

2.Use features

For crossed roller bearings, since the divided inner ring or outer ring is installed with rollers and spacers, it is fixed with the crossed roller collar to prevent separation from each other, so it is necessary to install the crossed roller collar. Simple.

Since the rollers are arranged in a cross, only one set of Cross Roller Rings can withstand loads in all directions, and the rigidity is 3 to 4 times higher than that of conventional models.

At the same time, since the inner ring or outer ring of the crossed roller bearing is divided into two structures, the bearing clearance can be adjusted, and even if a preload is applied, high-precision rotational motion can be obtained.

1. Excellent rotation accuracy

The internal structure of the crossed roller bearing adopts the rollers arranged at 90° perpendicular to each other.

There are spacers or spacers between the rollers, which can prevent the rollers from rubbing against each other due to the inclination of the rollers.

In addition, there is no contact phenomenon or locking phenomenon of one side of the roller; at the same time, because the inner and outer rings are divided structures, the gap can be adjusted, and even if a preload is applied, high-precision rotational motion can be obtained.

2. Simplified operation and installation

The outer ring or inner ring, which is divided into two parts, is fixed together after the rollers and cages are installed, so it is very easy to install.

3. Bear large axial and radial loads

Because the rollers are arranged perpendicular to each other on the 90° V-groove running surface by spacers.

4. Significantly save installation space

The size of the inner and outer rings of the crossed roller bearing is minimized, especially the ultra-thin structure is a small size close to the limit, and has high rigidity, so it is most suitable for the joint parts or rotating parts of industrial robots, and the rotation of machining centers.

Widely used for worktables, manipulator rotating parts, precision rotary tables, medical instruments, measuring instruments, IC manufacturing equipment, etc.

5. High speed capability

6. Reduced shaft length and machining cost, limited change in geometry due to thermal expansion

7. Using nylon divider, low moment of inertia, low starting torque, easy to control angle indexing

8. Optimized pre-tightening force, high rigidity and high running accuracy of guide rollers

9. Carburized steel provides excellent impact resistance and surface wear resistance

10. Simple but well lubricated

Classification and Model Series of Domestic Crossed Cylindrical Roller Bearings

RB type (outer ring split type)

The RB series is the basic type of the crossed cylindrical roller bearing. The inner and outer rings are minimized in size. The structure is that the outer ring is a split type and the inner ring is an integral design. It is suitable for parts that require high rotation accuracy of the inner ring. .

RE type (inner ring split type)

The RE series model is a new type produced by the design concept of the XRB type, and the main dimensions are the same as the XRB type. Its structure is that the inner ring is a split type, and the outer ring is a one-piece design, which is suitable for parts requiring high rotation accuracy of the outer ring.

RU type (inner and outer ring integrated type)

The RU series model does not need a fixed flange and a support seat due to the machining of the mounting holes. In addition, since the integrated inner and outer ring structure with seat is adopted, installation has little effect on performance, so stable rotation accuracy and torque can be obtained. Can be used for outer and inner ring rotation.

RBC type (outer ring split type)

The RBC series model (corresponding to the CRBC series of IKO company) has a structure that the outer ring is a split type, the inner ring is an integral design, and a full complement roller bearing with a cage. It is suitable for parts that require high rotation precision of the inner ring.

CRBH type (inner and outer ring integrated type)

The inner and outer rings of the CRBH series are of one-piece structure for rotation of the outer and inner rings.

RA type (outer ring split, ultra-thin type)

The RA series model is a compact model that reduces the thickness of the inner and outer rings of the RB type to the limit. Ideal for applications requiring a lightweight, compact design, such as robotic and manipulator rotation.

SX type (outer ring split type)

The structure of SX series models is similar to that of RB series. The outer ring is a two-part structure, connected by three spring snap rings, and the inner ring is designed as one piece, which is suitable for places requiring high rotation precision of the inner ring.

XRU08 type (integrated type of inner and outer rings)

The XSU08 series is similar to the RU series, and the inner and outer rings have been processed with mounting holes, so there is no need for a fixed flange and a support seat.

Due to the integrated inner and outer ring structure with seat, installation has little effect on performance, so stable rotation accuracy and torque can be obtained. Can be used for outer and inner ring rotation.

First thrust angular contact ball bearing

The contact angle of thrust angular contact ball bearings is generally 60°. Commonly used thrust angular contact ball bearings are generally bidirectional thrust angular contact ball bearings, which are mainly used for precision machine tool spindles.

It has the advantages of high precision, good rigidity, low temperature rise, high speed, and convenient assembly and disassembly.

Second deep groove ball bearing

Structurally, each ring of a deep groove ball bearing has a continuous groove-type raceway with a cross-section of approximately one third of the equatorial circumference of the ball.

Deep groove ball bearings are mainly used to bear radial loads, and can also bear certain axial loads. When the radial clearance of the rolling bearing increases, it has the properties of an angular contact ball bearing and can bear axial loads alternating in two directions.

Compared with other types of bearings of the same size, this type of bearing has a small friction coefficient, high limit speed and high precision, and is the preferred bearing type for users when selecting models. Deep groove ball bearings have a simple structure and are easy to use. They are the type of bearing with the largest production volume and the widest application range.

Third thrust tapered roller bearing

Since the rolling elements in the thrust tapered roller bearing are tapered rollers, the rolling busbar and the raceway busbar of the washer meet at a certain point on the axis of the bearing, so the rolling surface can form pure rolling and high limit speed. for thrust cylindrical roller bearings.

Features: Thrust tapered roller bearings can withstand unidirectional axial loads. The type code of thrust tapered roller bearing is 90000 type.

Introduction to Crossed Cylindrical Roller Bearings

There are two types of crossed roller bearings, one is crossed cylindrical roller bearings, the other is crossed tapered roller bearings; crossed roller bearings have a long history of application abroad, but only recently in China.

It has only entered the public’s vision for a few years, and it is widely used due to its own particularity and incomparable advantages over other bearings.

cheap crossed roller slewing bearings manufacturers china

Crossed Roller Slewing Bearings

A crossed roller slewing bearing is a special type of bearing with a split inner ring and a rotating outer ring. Since the divided inner ring or outer ring is installed with the roller and spacer, it is fixed with the cross roller ring to prevent separation from each other, so it is easy to install the cross roller ring.

Since the rollers are arranged in a cross, only one set of Crossed Roller Slewing Bearings can withstand loads in all directions, and the rigidity is 3 to 4 times higher than that of conventional models. At the same time, since the inner ring or outer ring of the crossed roller slewing bearing is divided into two structures, the bearing clearance can be adjusted, and even if a preload is applied, high-precision rotational motion can be obtained. Moreover, due to its special structure, it is usually used as a joint bearing in industrial robots.

Their rollers are arranged at right angles to each other at intervals between the inner and outer wheels. They can bear loads from all directions at the same time (such as axial, thrust or momentum loads, etc.). Because the rollers are in linear contact with the track surface, the possibility of elastic deformation of the bearing under load is very small.

This type of bearing is widely used in such occasions as industrial automatic robots, working machinery and medical facilities, etc., where high rigidity, tightness and high speed are required to ensure accuracy.

In a crossed roller slewing bearing, since the cylindrical rollers are arranged perpendicular to each other through spacers, a single crossed roller bearing can withstand loads in all directions, including radial load, axial load, and moment load.

The size of the inner and outer rings is minimized, especially the ultra-thin type is a small size close to the limit, and has high rigidity, so it is most suitable for the joint part or rotating part of industrial robots, the rotary table of machining center, It is used for robot rotating parts, precision rotary tables, medical equipment, measuring instruments, IC manufacturing equipment, etc.

Use features
For crossed roller bearings, since the divided inner ring or outer ring is installed with the rollers and spacers, it is fixed with the crossed roller collar to prevent separation from each other, so it is necessary to install the crossed roller collar.

Simple. Since the rollers are arranged in a cross, only one set of Crossed Roller Slewing Bearings can withstand loads in all directions, and the rigidity is 3 to 4 times higher than that of conventional models. At the same time, since the inner ring or outer ring of the crossed roller bearing is divided into two structures, the bearing clearance can be adjusted, and even if a preload is applied, high-precision rotational motion can be obtained.

crossed roller slewing bearing Alt.

1. Excellent rotation accuracy

The internal structure of the crossed roller slewing bearing adopts the rollers arranged at 90° perpendicular to each other.

There are spacers or spacers between the rollers, which can prevent the rollers from rubbing against each other due to the inclination of the rollers. In addition, there is no contact phenomenon or locking phenomenon of one side of the roller; at the same time, because the inner and outer rings are divided structures, the gap can be adjusted, and even if a preload is applied, high-precision rotational motion can be obtained.

2. Simplified operation and installation

The outer ring or inner ring, which is divided into two parts, is fixed together after the rollers and cages are installed, so it is very easy to install.

3. Bear large axial and radial loads

Because the rollers are arranged perpendicular to each other on the 90° V-groove running surface by spacers.

4. Significantly save installation space

The size of the inner and outer rings of the crossed roller bearing is minimized, especially the ultra-thin structure is a small size close to the limit, and has high rigidity, so it is most suitable for the joint parts or rotating parts of industrial robots, and the rotation of machining centers. Widely used for worktables, manipulator rotating parts, precision rotary tables, medical instruments, measuring instruments, IC manufacturing equipment, etc.

5. High speed capability

6. Reduced shaft length and machining cost, limited change in geometry due to thermal expansion

7. Using nylon divider, low moment of inertia, low starting torque, easy to control angle indexing

8. Optimized pre-tightening force, high rigidity and high running accuracy of guide rollers

9. Carburized steel provides excellent impact resistance and surface wear resistance

10. Simple but well lubricated

Classification and Model Series of Domestic Crossed Cylindrical Roller Bearings

RB type (outer ring split type)

The RB series is the basic type of the crossed cylindrical roller bearing. The size of the inner and outer rings is minimized. Its structure is that the outer ring is a split type, and the inner ring is an integral design, which is suitable for parts that require high rotation accuracy of the inner ring. .

RE type (inner ring split type)

The RE series model is a new type produced by the design concept of the XRB type, and the main dimensions are the same as the XRB type. Its structure is that the inner ring is a split type, and the outer ring is a one-piece design, which is suitable for parts requiring high rotation accuracy of the outer ring.

RU type (inner and outer ring integrated type)

The RU series model does not need a fixed flange and a support seat due to the machining of the mounting holes. In addition, since the integrated inner and outer ring structure with seat is adopted, installation has little effect on performance, so stable rotation accuracy and torque can be obtained. Can be used for outer and inner ring rotation.

RBC type (outer ring split type)

The RBC series model (corresponding to the CRBC series of IKO company) has a structure that the outer ring is a split type, the inner ring is an integral design, and a full complement roller bearing with a cage. It is suitable for parts that require high rotation precision of the inner ring.

CRBH type (inner and outer ring integrated type)

The inner and outer rings of the CRBH series are of one-piece structure for rotation of the outer and inner rings.

RA type (outer ring split, ultra-thin type)

The RA series model is a compact model that reduces the thickness of the inner and outer rings of the RB type to the limit. Ideal for applications requiring a lightweight, compact design, such as robotic and manipulator rotation.

SX type (outer ring split type)

The structure of the SX series is similar to the RB series. The outer ring is a two-part structure, connected by three spring snap rings, and the inner ring is designed in one piece, which is suitable for places requiring high rotation precision of the inner ring.

XRU08 type (integrated type of inner and outer rings)

The XSU08 series is similar to the RU series, and the inner and outer rings have been processed with mounting holes, so there is no need for a fixed flange and a support seat. Due to the integrated inner and outer ring structure with seat, installation has little effect on performance, so stable rotation accuracy and torque can be obtained. Can be used for outer and inner ring rotation.

First thrust angular contact ball bearing
The contact angle of thrust angular contact ball bearings is generally 60°. Commonly used thrust angular contact ball bearings are generally bidirectional thrust angular contact ball bearings, which are mainly used for precision machine tool spindles. It has the advantages of high precision, good rigidity, low temperature rise, high speed, and convenient assembly and disassembly.

Second deep groove ball bearing
Structurally, each ring of a deep groove ball bearing has a continuous groove-type raceway with a cross-section of approximately one third of the equatorial circumference of the ball. Deep groove ball bearings are mainly used to bear radial loads, and can also bear certain axial loads. When the radial clearance of the rolling bearing increases, it has the properties of an angular contact ball bearing and can bear axial loads alternating in two directions.

Compared with other types of bearings of the same size, this type of bearing has a small friction coefficient, high limit speed and high precision, and is the preferred bearing type for users when selecting models. Deep groove ball bearings have a simple structure and are easy to use. They are the type of bearing with the largest production volume and the widest application range.

Third thrust tapered roller bearing
Since the rolling elements in the thrust tapered roller bearing are tapered rollers, the rolling busbar and the raceway busbar of the washer meet at a certain point on the axis of the bearing, so the rolling surface can form pure rolling and high limit speed. for thrust cylindrical roller bearings. Features: Thrust tapered roller bearings can withstand unidirectional axial loads. The type code of thrust tapered roller bearing is 90000 type.

Introduction to Crossed Cylindrical Roller Bearings

There are two types of crossed roller slewing bearings, one is crossed cylindrical roller bearings, the other is crossed tapered roller bearings; crossed roller bearings have a long history of application abroad, but only recently in China. It has only entered the public’s vision for a few years, and it is widely used due to its own particularity and incomparable advantages over other bearings.

Crossed Roller Bearings

Crossed-roller bearings are bearings for high-precision applications whose dimensions conform to ISO dimension series 18 as per DIN 616. They comprise outer rings, inner rings, rolling elements and plastic spacers. The outer ring is split and is held together by three retaining rings.

Due to the X arrangement of the cylindrical rollers, these bearings can support axial forces from both directions as well as radial forces, tilting moment loads and any combination of loads by means of a single bearing position. As a result, designs involving two bearing positions can be reduced to a single bearing position.

Crossed roller bearings are very rigid, have high running accuracy and are supplied with normal clearance, low clearance or preload. The bearing outer rings are easily fixed to the adjacent construction using clamping rings.

The Basis of crossed roller bearings

Crossed roller bearings provide more accuracy, rigidity, and weight-bearing capacity for linear motion than other commonly used friction-reducing devices such as ball bearings. And unlike ball bearings, they can support moment loads, radial forces or tilting loads. This lets one crossed roller bearing replace more than one ball bearing, thus saving the space required by ball bearings, lowering the associated material costs.

Crossed roller bearings are preferred for high-precision linear-motion applications with relatively short linear movements that require smooth motion. They are also durable, lasting 150 million cycles, even for linear-motion applications with high levels of acceleration and deceleration when using 2 to 12-mm rollers and 30 to 600-mm lengths.

They can be found in medical and lab equipment, machine tools, semiconductor processing, clean rooms, vacuum environments, material handling, and automation machinery. And as technology becomes more demanding, requiring greater and greater precision, crossed roller bearings will also become more common.

Crossed Roller Bearing Basics

A crossed roller bearing, also called a crossed roller slideway, is effectively two sets of
bearings and races combined at right angles to each other. Cylindrical bearings or rollers mount along the length of a rail in a carriage. The rollers are held in place with a cage, preventing roller-to-roller contact, which increases friction and wear. Keeping rollers separated also eliminates any risk of them jamming.

If you were to number the cylindrical rollers along the rail, the even ones would be mounted at 90° to the odd ones. In other words, the rollers alternate orientation. This lets the line of alternating rollers support loads from all directions, including high overturning moments, and because they do not recirculate like some ball bearings that line linear rails, all the rollers are constantly carrying the load except for pure radial loads, where, due to the criss-cross arrangement, only half of the rollers take loads at any one time.

The cylindrical rollers are mounted such that they create a protruding V-shape on the sliding rail. It fits into a corresponding V notch in the other rail that is likely carrying
the load.

crossed roller bearing

Rollers provide a full line of contact rather than just the point of contact a ball bearing provides. This gives crossed roller bearing a broader contact surface and the ability to carry heavier loads. It also increases the bearing’s rigidity so it deforms less and is thus more accurate. Plus, erosion is slower due to the crossed rollers’ consistency of contact between the carriage and the base.

There is a direct correlation between the combined contact area of all the rollers and load capacity: the greater the area, the higher the capacity. This lets bearing designers adjust load capacity by up to 250% by mounting rollers closer together. This permits more rollers to fit in the same space and increases the amount of weight per inch the bearing can carry.

Cross roller bearing do not use seals due to their construction, high precision, and low friction. Still, it is important to keep contaminants away from the rollers to prevent damage and wear. One way this is done, especially in IC manufacturing and lab equipment, is to install the machines using crossed roller bearings in clean, contamination-free environments.

It is also important to lubricate crossed roller bearings to get the most operational life out of them. A standard lubricant for them is lithium-soap-based #00 grease.

The configuration of crossed roller bearings gives designers all the benefits of a two-row bearing, including stability, in a single-row space.

Accuracy and Rails

Because of crossed rollers large contact area, they deform less than recirculating ball bearings and are stiffer, creating more precise and consistent motion. Because of this greater stiffness, crossed rollers provide consistently precise movement.

Crossed rollers are less forgiving of mounting surface inaccuracies than recirculating ball bearings due to their rigidity and the way they are designed. Ball bearings can handle imperfections on the order of five to ten 10 microns while crossed roller bearings need imperfections smaller than two microns for ultra precision.

Metal and Plastic Cages

One factor that determines how close rollers can be to each other is the cage (or retainer) holding them all in place, so its design is critical. An important factor in the design of the cage is whether it is made of metal or plastic.

Traditional metal cages use tabs on the carriage that fit into notches on the top and bottom of the rollers to keep them in place. This limits how closely a roller can be positioned between neighboring rollers, which then limits the crossed roller bearing’s load-carrying capacity.

But metal cages are less expensive and can be plain or stainless steel. Metal is more compatible with working in vacuums, including outer space, because plastic can out-gas and cause problems with electronics and optics. Stainless steel can also be beneficial in high-temperate applications and those requiring washdowns and where rust is unacceptable.

Plastic cages fit smoothly around each roller, exposing more of it to the load than a metal cage can. Plastic cages also pack rollers closer together so more rollers can be housed in the same rail. These two features mean the cage and rollers can be shorter while maintaining the same load capacity or the number of rollers can be increased within the same cage (compared to a metal version) and thus increase the load capacity. In fact, a plastic cage can yield a 30% to 58% increase in contact area compared to a metal cage. This increase translates to a 250% increase in load capacity.

Recent development in plastic cages has increased the number of design options available to engineers. They can now be shaped so that there’s even a larger contact area with less space between rollers. Plastic cages can also be thinner in critical areas.

Preventing Cage Creep

Metal and plastic cages both effectively float between the bearing’s rails and they both tend to drift away from the bearing’s longitudinal center over time, a phenomenon called cage creep. It happens when the linear bearing only makes partial strokes, especially when mounted vertically. The cage can restrict slide travel because once the cage has moved and the bearing makes its next full stroke, the off-center cage hits a rail endstop and is forced to center itself by skidding.

Hitting the endstop and skidding can damage the retainer, rollers, and slideway. And it could require a more powerful and expensive motor to offset the effects of creep. Cage creep also means the rollers are not rolling but slipping and causing metal-to-metal rubbing, which leads to wear.

If a crossed roller bearing has no defense against creep, technicians will often have to regularly readjust the linearmotion equipment and replace worn components. Creep
is particularly bad when applications require high levels of acceleration and deceleration, uneven preloading or load distribution, or vertical or inclined strokes.

Fortunately, there are anti-creep mechanisms that stop retainers from slipping by holding the rollers between the two V-grooved slideway rails. As a result, the rails can be used in any mounting orientation, and lower-momentum motors such as linear motors can be used to move the loads. Anti-creep devices also reduce downtime and the cost of maintenance.

One anti-creep device, a rack-and-pinion mechanism, consists of external plastic gears and a metal gear inside the rail. Though effective, this approach is costly and makes it impossible to change out failed or worn bearing components.

Another approach to preventing creep uses rollers with spherical studs circling the middle of the roller’s round surface. As the rollers turn in the rail, they mesh with a row of holes or dimples machined down the exact center of the raceway tracks. This design, called Studroller at NB, prevents slipping regardless of the rail’s orientation or position. It creates smoother tracking motion than gear-based anti-creep mechanisms, so it is quieter and more accurate. Keeping the rollers aligned along the center of the rail also keeps all components aligned.

With the Studroller approach, the number of effective rollers increases by 20% to 55%. Contact area between rollers and the raceway surface jumps by 42% to 58%, which lets the load rating increase by 140% to 230%. This should lead to savings in cost and space required to mount the linear bearing.

Costs vary for crossed roller bearings with anti-creep devices depending on the complexity of the device whether the application must be custom designed and manufactured to accommodate them. The Studroller approach, being the simplest non-slip design, is priced the same as a standard crossed roller slideway, which is roughly half the cost of other anti-creep devices. And there are no redesign costs to replace a standard slideway.

Travel Lengths

For crossed roller bearings on linear sliderails, the rails’ lengths determine the length of the stroke or travel. The entire rail assembly must be twice as long as the stroke. That’s because both rails containing crossed roller bearings move in opposite directions. That means the whole assembly has to have room to move inside a space twice as long as the travel length. (Recirculating-ball bushings used for linear motion need shafts only as long as the required travel because the only moving component is the bushing.)

When the bearing uses plastic cages, stroke length can be longer on a given length of rail because the cage can be shorter for a given load.

So one limit on a crossed roller bearing’s travel is the space available in the application. As mentioned, with the rails moving in opposition to each other, the overall space required is twice the distance the load will travel. Endstops are components mounted on linear rails that physically limit travel length, stopping the rails from going farther.

Ratings and Life

The dynamic load ratings of crossed rolling bearings are based on the industry standard of 50 km of travel. In effect, it means that when you purchase several crossed bearings, 90% of them will last at least 50 km under normal operating conditions at its rated load. Using bearings with load ratings higher than an application requires usually lets the bearing last longer or withstand more demanding conditions.

It’s also important to select bearings with a margin of extra load capacity if accuracy is paramount. That’s because rollers and rails can deform when nearing their load limits, which can change the accuracy, sometimes permanently.