Profile rail guides – Types / function / service life / maintenance / alternatives

Profile rail guides: Join us as we explore the world of profile rail guides. Our article highlights the different types of profile rail guides and their functions. Learn how to maximize service life with proper maintenance, and take a look at possible alternatives in this critical area of linear motion technology.

General description of profile rail guides

Profile rail guides are mechanical components that are intended to enable a guided linear movement. These systems can be adapted to specific requirements and are used under a wide range of operating conditions thanks to their different versions and designs. Their uses range from a harsh and demanding operating environment to high-precision process automation.

Likewise, they have proven themselves in many industries and industrial automation. Without limitation, profile rail guides are used in mechanical engineering and custom machine construction, pharmaceutical engineering, medical equipment, the food industry, and in conveyor technology. Profile rail guides are also often used for packaging machines and palletizers. The application and integration in handling technology and automation is now common practice.

Types of profile rail guides

A profile rail guide is an option commonly used in mechanical engineering to enable linear movement with fixed degrees of freedom. Depending on the design and type of the linear guide, the linear movement can occur on a straight and also on a curved path.

Linear guides can be distinguished by the type of bearing arrangement.

Linear bearing units, for example, make use of round or rectangular rods that can be guided by one or more linear ball bushings or plain bearing bushings or ball bearing bushings.

In this article, we primarily discuss the profile rail guide with rolling body bearing and plain bearing.

Description and function of profile rail guides

Profile rail guides are devices for guiding and positioning linear motion. The linear motion is guided by a profile rail and by one or more guide carriages. Forces from all transverse directions are absorbed.

Depending on the requirements, the profile rail can be made of steel, stainless steel or can also be surface treated accordingly.

Rolling bearing profile rail guides use rolling bodies as a bearing arrangement between the linear rail and the guide carriage, often referred to as a carriage. Balls, rollers, or needles can be used as roller bodies, wherein the various designs differ primarily in the coefficient of friction, the load-bearing capacity, and the package size.

The acting forces are absorbed and dissipated by the rolling bodies. Rolling bearings with rollers can absorb very high load capacities. Additional separator elements are used to prevent contact between the roller bodies. This approach typically involves making use of a rolling body cage or also a rolling body chain. This design reduces noise, vibration, and wear, thus making maintenance easier and more convenient.

Depending on the rail geometry and the selection of the roller body, a corresponding load distribution is created on the contact surfaces of the raceway, which affects the load capacity and friction resistance. Due to the relatively small contact surface between the roller body and the raceway of the guide rail, the coefficient of friction is very low compared to the slide guides, which requires a very low starting torque and generates less friction-induced heat.

Despite its dead weight, rolling bearing systems have proven themselves when transporting higher loads at high acceleration and travel speeds. If high precision is required for the profile rail guide, the required rigidity of the guide system can be achieved with a correspondingly high preload. A profile rail guide with low preload is characterized above all by ease of movement and less wear and tear, accompanied by lower precision.

The use in sensitive areas of medical equipment, the pharmaceutical industry and electronics processing as well as in a clean industrial environment and cleanroom technology places high demands on sealing and lubricating linear guides. Versions with special seals, covers and lubrication options are available here.

Seals and wipers can be provided on all sides to protect profile rail guides against dirt and particle ingress. Depending on the seal material and the mounting concept, high leak-tightness also has a resistance effect on the raceways. Regular maintenance and servicing is necessary in any case. Appropriate lubrication is also essential to prevent corrosion and to reduce friction and wear.

Selecting the right lubricant plays a decisive role in this. The circulation principle exerts a uniform load on all rolling elements and the lubricant introduced can be distributed evenly. The profile rail and also the guide carriage can be coated according to the respective application of the profile rail guide. The roller bodies are generally not coated. They are protected against corrosion by regular lubrication.

In addition to roller bearings in traditional mechanical engineering and custom machine construction, slide guides are the most frequently used type of bearing. Plain bearings have a simple design and have no moving parts. As a result. they have only a very low dead weight, which must be accelerated during travel.

For plain bearing guides, the sliding surfaces are made of special materials, treated by a suitable coating and, if necessary, suitable lubricants are used to achieve the lowest possible sliding friction. It is also possible to embed a dry lubricant in the materials of the sliding guide, which enables grease-free and oil-free lubrication. This type of lubrication reduces the amount of dirt in the guide rail. The plain bearing bushing pushes adhering dirt particles off the guide rail. Compared to rolling bearings, plain bearings have a relatively large contact surface between the sliding body and the bearing surface, which makes them more resistant to external influences such as vibrations and shocks. In addition to very good vibration damping, they are often characterized by good emergency running properties.

A major advantage of sliding guides is their low weight, which enables extremely high acceleration and travel speeds when transporting smaller payloads. Another advantage is the low noise emission that remains constant over the travel distance.

Maintenance and lubrication of profile rail guides

An intelligent lubrication concept increases the service life, reduces maintenance intervals to a minimum and keeps maintenance costs low.

Linear guides and profile rail guides must be lubricated regularly to reduce friction and wear. The lubrication interval varies depending on the application and ambient conditions.

Excessive lubricant should not be introduced into the linear guide, as excessive lubricant can lead to increased resistance and damage.

We recommend checking the lubrication performance at shorter intervals and to adjust it gradually to the local operating conditions.

For smaller profile rail guides, such as miniature linear guides, the linear guide can be lubricated over the linear rail. For this purpose, the lubricant can be applied to the raceways of the linear rail. Larger linear guides often have guide carriages with a lubrication adapter to guide the lubricant to the desired locations.

There are various lubricants and lubrication types that can be used in linear guides. Whether oil lubrication or grease lubrication makes sense depends on the design of the bearing, the requirements and the operating conditions. Lubrication can be performed in different ways.

For manual lubrication, the lubricant is fed to the lubrication points by hand with a brush, oil can or grease gun. For service life lubrication, the materials are already provided with lubricant ex works, which is sufficient for the service life of the bearing. To prevent premature leakage or contamination of the lubricant, the lubrication points are secured by seals and covers.

In addition to lubrication, it is of course important to monitor the state of the linear guide by regular inspection and maintenance.

This includes regular visual inspection of the components and the profile rail for signs of wear, abrasion and contamination. Regular cleaning of the guide tracks and, if necessary, other activities to be taken from the maintenance plan of the assembly instructions must also be carried out.

Linear Guide Service Life

In order to determine the service life, it is necessary to define the operating conditions and load capacity. This depends not only on the applied load, the starting torque and the lubrication, but also on many other influence factors.

After determining the rated load capacity, the useful life of a profile rail guide can be calculated depending on the application.

The following links provide information needed to calculate the useful life of a linear guide and the design of profile rail guides.

Link to calculation part 1

Link to calculation part 2

Calculation tool

Alternatives to profile rail guides

Dovetail guides are a possible alternative to profile rail guides, especially in applications that require high load capacity, stability and precision.

Dovetail guides consist of a trapezoidal recess and a matching guide rail. The carriage has a dovetail that fits into the guide rail. This structure offers a stable and low-friction guide. Dovetail guides are usually designed for high loads and can carry heavy workpieces. They offer high precision and repeatability, making them suitable for tight tolerance applications.