Applications of Linear Rails.

Linear rails are linear assemblies with twin parallel rails containing balls or bearing rollers. The backbone of many industrial applications, providing low-friction, high-rigidity guidance for loads ranging from a few grams to thousands of kilograms. Due to their various sizes, accuracy classes, and preloads, linear rails are suitable for almost any performance requirement.

There are many reasons to use a linear rail, but the most obvious advantages over other types of guides are load capacity, travel precision, and stiffness. For example, circular axle guides can only support downward or lifting loads, while linear rail guides can support both downward / lifting loads and momentary loads. Also, unlike cross roller guides where travel distance is limited to less than 1 meter, linear rails can provide very long travel lengths. Compared to plain bearing guides, linear rails are highly rigid and rigid, and often have better load / life characteristics.

Linear guides precisely machine one or both edges of the rail to provide a high level of movement precision that acts as a reference plane. And with two, four, or six rows of rolling elements, such as spherical balls or cylindrical rollers, stiffness is high and deflection of the bearing block is minimized. All of these properties combine to provide a linear guide system that is perfectly suited for applications requiring high precision, high rigidity and long life.

Single lane application:-

Linear rails have load bearing balls (or rollers) on each side of the rail, allowing it to withstand cantilever loads even with a single rail. Conversely, if you have a cantilever load, you should use a circular axis linear guide in pairs, this feature saves space by using a single linear rail in many applications or avoids misalignment problems between different system components. Here are some examples of applications that use a single linear rail.

Linear Actuators:- Linear rails are often guide mechanisms for actuators driven by belts, screws, or pneumatic cylinders due to their ability to support moment loads. It can also accommodate travel speeds of up to 5m / sec, which is important in belt or pneumatic drive systems.

Linear actuators often incorporate a single linear rail with one or two support blocks.

Overhead Transport System:- As with load  transport systems, it is recommended to use a linear rail when the load is centered below the rails and support blocks. It can carry heavy loads with high load capacity, and the stiffness of the linear rail helps strengthen the entire system.

Gantry Robot:- A feature of the gantry is that it has two X-axis axes (sometimes two Y and two Z axes). Individual shafts generally contain a single linear rail and are driven by a screw or belt and pulley system. When two axes work in parallel (eg X and X '), very good moment capacity is achieved even if there is only one linear rail on each axis.

When two axes operate in parallel, the moment capacity is very high, even if there is only one linear rail on each axis. This example shows two X axes (each with a linear rail), one Y axis, and one Z axis.

Dual rail application:-

Linear rails can be used in pairs in the presence of high moment loads, allowing moment loads to be interpreted as the forces of a supporting block. In this configuration, the drive mechanism can be mounted between linear rails, making the entire system very compact. Dual linear rail applications include:

Linear stage:-  Stages are generally high-precision systems, so high movement precision and minimal deflection are paramount. Even when the load is in the center of the stage with little or no moment load, double linear rails are often used to maximize rigidity and bearing life.

Linear rails are often used in stages that require longer strokes than can be provided by air bearings or cross roller sliders.

Machine tools:-  Machine tools, like stages, require a high level of movement precision and stiffness to produce high-quality parts. By using 2 rails in parallel with 2 support blocks per rail, buckling can be minimized. Machine tools also experience very high loads, so solving the load on all four bearing blocks can maximize bearing life.

Depending on the load capacity and rigidity requirements of the machine tool, it is often necessary to use double linear ball or roller rails.

Cartesian robots:-  Cartesian robots usually use a linear system per axis, so each axis must be able to withstand high moment loads. This is the reason why most of the axes of the Cartesian robot consist of linear actuators that contain two linear guides in parallel.

The Cartesian robot consists of individual axes using dual linear rails, such as the ball screw actuated double rail actuator shown here.

Robotic Transport Device:- 6-axis robots provide flexible movement for applications that need to reach and rotate in multiple directions. However, if the robot needs to move to another station or work area, the dual rail system can act as a "seventh axis" to transport the entire robot to a new location. The main advantage of linear rails in these applications is the ability to combine multiple rails for very long runs (generally more than 15 meters).

Definitely, linear rails are not the perfect solution for all applications. Linear rails, for example, are generally not suitable for consumer space applications such as door guides and drawer slides due to their cost. In addition, linear rails require a very precise mounting surface, which not only benefits from high movement precision, but also avoids restriction of the support block, which can shorten the service life. It must also be fully compatible, unlike a linear axis system that can only end the bracket. This means that the prepaid cost of a linear rail is generally higher than the cost of a circular shaft or a plain bearing system, as well as the cost of set-up and mounting.

Linear rails can be perceived as less smooth or "notched" in driving characteristics than other types of bearings. This is due to the contact between the load transport ball (or the roller) and the surface of the raceway. Preloading a linear rail system that is often done to increase stiffness can exacerbate the "notch" feel when the support block is moved along the rail. (This effect disappears when a load is applied to the bearing, but recognition often remains.)

For applications that do not require load capacity, rigidity, or driving precision of linear rails, other linear guides such as circular axis systems, flat bearing guides, or cross roller sliders may be suitable and inexpensive.