Linear ball carriages for profile rail guides

What are linear ball bearing carriages and what are they used for?

A linear ball bearing in the form of a carriage is part of a profile rail guide that travels along the rail and carries a machine component, table, tool holder or other moving assembly. The rail defines the axis of motion, while the carriage takes up the loads and transfers them to the rail.
Unlike plain (sliding) guides, the carriage does not slide on the rail; instead, balls roll along it. Friction is therefore low and uniform, and motion can be precise even at higher speeds and with frequent strokes.
Profile rail guides with ball carriages are today a standard solution in mechanical engineering wherever a combination of accuracy, rigidity and load capacity from several directions is required. They are used in machine tools, gantry systems, robot axes, assembly equipment and many other applications.
This category contains carriages only. The matching rails are in the ball guides category, where you can select a rail from the same manufacturer, series and size.

How does a ball carriage work?

The carriage body contains raceways along which the balls move. As the carriage travels along the rail, the balls in the loaded zone roll between the carriage and the rail and then recirculate through a return channel in the end cap back to the start of the loaded zone.
This recirculation of the rolling elements allows an unlimited stroke length, determined only by the length of the rail. A carriage usually has several rows of balls arranged so that it can take up loads in the vertical and horizontal directions as well as moments about all three axes.
The carriage also includes end seals that keep out contamination and a lubrication nipple through which lubricant reaches the raceways. For some series, additional seals, scrapers or lubricant reservoirs are available, depending on the manufacturer and version.

Main features of linear ball carriages

The properties of a carriage depend on its series, size, body shape, preload and accuracy class. The most important features include:

• low friction and uniform displacement force,
• precise and repeatable guidance along the rail,
• load capacity from several directions and for moments,
• unlimited stroke length, determined by the rail length,
• different body shapes for different mounting methods,
• choice of preload level according to the required rigidity,
• choice of accuracy class according to the required precision,
• lubrication with grease or oil,
• seals for protection against contamination,
• interchangeability of carriages within the same series for versions where the manufacturer permits it.

A carriage only works correctly in combination with a suitable rail. Size, series and accuracy class must be matched; otherwise uneven running, increased wear or problems during mounting may occur.

Types of ball carriages in the M&M Intercom range

Our range includes ball carriages for standard profile rail guides, miniature guides and wide guides. They differ mainly in body shape, height, length and mounting method.

Flanged ball carriages

Flanged carriages have a wider body with a flange that allows the machine component to be fastened from above or from below. They are suitable for applications where secure mounting and good load transfer to the structure are important.
In the Bosch Rexroth type code, these carriages are marked with the letter F, for example FNS or FLS. At Hiwin they can be recognised by versions such as HGW and EGW.

Narrow ball carriages

Narrow carriages have no flange and are fastened from above. They take up less space in width, which makes them suitable for compact designs.
At Bosch Rexroth they are marked with the letter S at the beginning of the type code, for example SNS, SNH, SKS or SLS. At Hiwin they are found among versions such as HGH, HGL and EGH.

Short, normal and long carriages

The body length affects the number of load-bearing balls and therefore the load capacity and rigidity. A longer carriage can generally take higher loads and moments, while a short one allows a longer usable stroke on the same rail and a shorter installation length.
At Bosch Rexroth, the second letter of the type code indicates the length (K short, N normal, L long) and the third the height (S standard, H high). SLH, for example, is a narrow, long, high carriage.

Low-profile ball carriages

Low-profile carriages have a smaller installation height and are intended for designs with limited space. The range includes Hiwin EG series carriages (EGH, EGW) and HGL versions, among others.

Miniature ball carriages

Miniature carriages are intended for small mechanisms, measuring equipment, electronics, optics and compact automation. Our range includes Bosch Rexroth MWA in sizes 7 to 20 and Hiwin MGN and MGW in sizes 5 to 15, among others.
With miniature guides, cleanliness, correct lubrication and careful mounting are particularly important, as the rolling elements are small.

Wide ball carriages

Wide carriages are designed for wider rails that provide greater stability under moment loads, especially when only one rail is used. Examples in our range are Hiwin WE series (WEH, WEW), wide Bosch Rexroth versions marked B and Bosch Rexroth LWA carriages.

Manufacturers and series of ball carriages

The category contains carriages from several manufacturers that differ in designations, dimensions and additional equipment. The most extensive range is from Bosch Rexroth, followed by Hiwin and other manufacturers.

Manufacturer	Example series in the range	Characteristic
Bosch Rexroth	KWD, KWC, MWA, LWA	Standard, miniature and wide carriages
Hiwin	HGH, HGW, HGL, EGH, EGW, MGN, MGW, QHH, QHW, WEH, WEW, CGH	Standard, low-profile, miniature and wide carriages
FAG INA	KWVE, KWSE	Carriages for FAG INA profile guides
TOCO, LSK	HGH, HGW, EGH, MGN, FL, GL	Carriages dimensionally comparable with individual series

In addition, the range includes individual carriages from NTN/SNR, PMI, TBI, NSK and SKF.
It is important not to combine a carriage from one manufacturer with a rail from another without checking compatibility. Even where designations or main dimensions are similar, the raceway profile, tolerances and preload may differ.

Preload of ball carriages

Preload means that the balls are fitted between the carriage and the rail with a slight oversize. This reduces or eliminates clearance and increases the rigidity of the guide.
The range includes carriages with different preload classes. At Bosch Rexroth they are designated C0, C1, C2 and C3, where C0 means a version without preload and a higher number means higher preload. At Hiwin the levels are designated ZF, Z0, Z1, ZA and ZB, depending on the series.
Higher preload increases rigidity and reduces deflection under load, but it also increases the displacement force and can affect service life. Lower preload is suitable for applications with lighter loads and a requirement for smooth running.
Check the exact meaning of each designation and the recommended field of application in the manufacturer's catalogue, as the classes differ between manufacturers and series.

Accuracy classes

The accuracy class defines the permissible deviations in height and lateral position of the carriage relative to the rail, as well as the differences between several carriages on the same rail.
Bosch Rexroth carriages in our range are available in accuracy classes N, H, P, SP, UP and XP, and Hiwin carriages mainly in classes C and H. The class must be matched to the rail and the requirements of the application.
For general automation and handling, normal or high classes are often sufficient. For machine tools, measuring equipment and systems with demanding motion geometry, higher accuracy classes are selected.

Seals, lubrication and maintenance

Seals prevent contamination from entering the carriage and keep the lubricant inside. For Bosch Rexroth carriages, the shop lists SS and DS seals, which differ in their sealing design. The choice depends on the environment and the required displacement force.
Lubrication is essential for the service life of the carriage. The lubricant reduces friction between the balls and the raceways and protects the surfaces against corrosion. The type of lubricant and lubrication intervals are determined according to the manufacturer's recommendations, taking into account speed, load, stroke length and environment.
Suitable greases and pastes for manual or central lubrication can be found in our lubricants range.
During maintenance we regularly check:

• cleanliness of the rail and carriage,
• condition of the end seals and scrapers,
• sufficient quantity of lubricant,
• smooth running and any noise,
• damage or corrosion of the raceways.

In dusty environments, with coolants or chips, additional protection is advisable, for example cover strips or additional seals from the accessories for rail guides.

Mounting ball carriages on the rail

When mounting a carriage, cleanliness and correct orientation are important. Slide the carriage onto the rail carefully and without impact, so as not to damage the seals or lose balls if the carriage has no ball retainer.
Mounting surfaces must be flat and clean, and the screws must be tightened to the torque specified by the manufacturer. With two parallel rails, correct parallelism and height alignment must be ensured; otherwise additional forces occur in the system.
Carriages are often supplied on a mounting rail that protects the balls during transport. The carriage is pushed from the mounting rail directly onto the working rail.

Use of linear ball carriages in industry

Ball carriages are used wherever precisely guided linear motion is required. Typical applications include:

• CNC machine tools and machining centres,
• gantry and Cartesian robots,
• assembly and test equipment,
• packaging and filling machines,
• handling and feeding systems,
• measuring and inspection equipment,
• woodworking machines,
• laser and plasma cutting machines.

To drive the axis, carriages are often combined with ball screws, toothed belts or linear motors. For fast assembly of axes, linear guide sets of rails and carriages are also available.

Ball or roller carriage – what is the difference?

With profile rail guides, you can choose between ball and roller carriages. Ball carriages have point contact between the rolling elements and the raceway, which allows low friction, smooth running and good performance at higher speeds.
Roller carriages have line contact and therefore achieve higher load capacity and rigidity for the same size. They are used mainly in heavy machine tools and applications with high loads.
For most applications in automation and general mechanical engineering, ball carriages are a suitable choice. Where maximum rigidity and load capacity are decisive, also consider linear roller bearings – carriages.

How to choose the right linear ball carriage?

When selecting a carriage, first determine the rail it will run on, or choose the rail and carriage together. Then check the requirements of the application. Important criteria are:

• manufacturer, series and size of the rail,
• magnitude and direction of loads and moments,
• required rigidity and thus the preload level,
• required accuracy and accuracy class,
• body shape and mounting method (flanged, narrow, wide),
• available installation height and length,
• speed and acceleration of motion,
• operating environment and required seals,
• lubrication method,
• required service life.

When replacing an existing carriage, the most reliable approach is to start from the complete designation on the carriage or the catalogue number. The designation contains information on the series, size, type, preload and accuracy class, which must be identical or matched to the rail.

Linear ball carriages available from M&M Intercom

At M&M Intercom we offer 3,000+ linear ball carriages for profile rail guides. Flanged, narrow, wide, low-profile and miniature versions are available in sizes 5 to 65, in different lengths, heights, preload classes and accuracy classes.
The range includes carriages from Bosch Rexroth, Hiwin, FAG INA, NTN/SNR and other manufacturers. In addition to carriages, our range includes linear guides, rails, sets, accessories and other linear technology components.
If you need to replace an existing carriage or are selecting components for a new axis, send us the designation or details of the application. We will help you choose a carriage that matches the rail, the loads and the required accuracy.

 

Frequently asked questions about linear ball carriages

1. What is a linear ball carriage?
A linear ball carriage is part of a profile rail guide that travels along the rail by means of recirculating balls. The moving machine component is mounted on it, and the carriage transfers the loads to the rail.
The balls in the carriage roll along the raceways and recirculate through return channels, allowing unlimited travel along the rail. The result is precise motion with low friction.
2. Can I buy a ball carriage without a rail?
Yes. This category contains carriages only, which you can order as spare parts or to complete an existing guide.
Rails are in the ball guides category. When purchased separately, the carriage and rail must belong to the same series and size from the same manufacturer, and the accuracy class must be matched.
3. Are carriages from different manufacturers interchangeable?
Not automatically. Although some series have similar mounting dimensions, the raceway profile, tolerances, preload and height may differ.
A carriage from one manufacturer should only be used on another manufacturer's rail if the manufacturer or the technical documentation explicitly confirms compatibility. Otherwise, always select a carriage from the same series as the rail.
4. What do preload designations such as C1 or ZA mean?
Preload designations indicate the oversize with which the balls are fitted in the carriage. Higher preload means higher rigidity and less deflection under load, but also a higher displacement force.
At Bosch Rexroth the classes are designated C0 to C3, and at Hiwin with designations such as ZF, Z0, Z1, ZA and ZB. The exact meaning of each class is defined in the manufacturer's catalogue.
5. Which accuracy class should I choose?
The accuracy class is chosen according to the required precision of motion. For general automation, normal or high classes such as N, H or C are often sufficient.
For machine tools and measuring equipment, higher classes such as P, SP or UP are used. The accuracy classes of the carriage and rail must be matched, as the accuracy of the system is determined by both elements.
6. What is the difference between a flanged and a narrow carriage?
A flanged carriage has a wider body with a flange and can be fastened from above or from below. A narrow carriage has no flange and is fastened from above, so it takes up less space in width.
The choice depends mainly on the design of the moving component and the available space. For the same size and length, both versions have comparable basic load characteristics.
7. When should I choose a miniature ball carriage?
A miniature carriage is chosen for small mechanisms where space is limited and loads are lower. Typical examples are measuring equipment, optical devices, laboratory automation and compact feeding systems.
Our range includes Bosch Rexroth MWA and Hiwin MGN and MGW miniature carriages. With these versions, cleanliness and proper lubrication are particularly important.
8. How often does a ball carriage need to be lubricated?
The lubrication interval depends on load, speed, stroke length, temperature and environment. Manufacturers specify recommended lubrication intervals and quantities for individual series and sizes.
In practice, the carriage is lubricated regularly via the lubrication nipple or with a central lubrication system. With short strokes, it is often necessary to move the carriage several times along its full travel during lubrication so that the lubricant reaches all raceways.
9. How do I select a replacement carriage for an existing guide?
The most reliable approach is to start from the complete carriage designation or the manufacturer's catalogue number. From it, the series, size, body type, preload and accuracy class can be determined.
If the designation is not legible, we need the manufacturer and series of the rail and the main dimensions of the carriage. Based on this information, we will help you find a suitable replacement.
10. How do I choose the right linear ball carriage for a new application?
First, determine the loads, moments, speed, stroke length and required accuracy. On this basis, select the size and series of the guide, and then the carriage shape, preload and accuracy class.
The selection should also take into account the installation space, mounting method, environment and lubrication. At M&M Intercom we will help you choose a carriage and matching rail that together ensure reliable operation of the linear axis.