Linear guides with own hands

Profiled linear guides, made or purchased with their own hands, are roller or ball high precision rolling bearings, which serve in linear movements. They have the ability to perceive forces acting in all directions, excluding the direction of movement.

Types of linear guides

Linear guides are of two types:

• With the circulation of balls;
• With the circulation of rollers.

Ball guides make two-, four- and six-row. They are miniature, suitable for use in a limited installation space. Linear guides are manufactured with different drives. Among them, more often there is a toothed belt or a ball screw drive (ball screw drives).

Roller made in the form of cylindrical guides and guides with a flat separator.

All guides must have the main properties:

• Small friction;
• High efficiency;
• Smooth linear movement;
• Ability to maintain operational parameters.

Linear Motion Modules

Recently, in connection with the development of automation, the use of linear displacement modules, which consist of:

• A strong bearing profile;
• Accurate guide system;
• Durable drive mechanism;
• Servo motor with simple control.

In such a modular component, the guides are used both with ball bearings and with roller bearings. The operating drive is carried out by means of a linear motor, a toothed belt or a ball screw mechanism.

The linear tables, which are used when large masses are to be moved along the axes, also found their application. Due to the dimensions, they perceive large moment loads. Linear tables use:

• Linear displacement bushings;
• Guides with the circulation of balls.

Method for measuring accuracy

If you make linear guides yourself, you need to control the accuracy. This is done quite simply. A rail is placed on the installed base surface. In this case, the accuracy is the expression of the mean value of the indicator readings in the central part of the measured surface. Also, the accuracy of linear guides is determined by measuring the width and length. In this case, the size tolerance for each block is measured, which is set on the rail.

Stiffness and preload

During operation, the profile rail guides undergo, due to the applied load, the elastic information. The indication of the magnitude of the deformation depends on the types of rolling elements. But somehow it becomes smaller when the load increases.

To increase the rigidity of the system, preload is applied. It reduces the life of linear guides, causing internal stress in them, but is also capable of absorbing deforming loads when the linear guide operates under conditions of strong vibration or impact load. Due to the fact that pre-tension causes elastic deformation of bearings, they become dependent on the negative effect of errors during installation. This suggests that more attention should be paid to the accuracy of machining the mounting surface.

Types of preload:

• Normal - it is applied in the presence of insignificant vibrations;
• Lightweight - used in the presence of light vibrations and light torque;
• Medium - it is used for shock loads and strong vibrations, as well as for overturning loads.

Mounting of rail guides

It is important to know that linear rail guides are subject to the action of force and torque. For them, the values should be determined: the permissible static moment and load-carrying capacity, which are calculated using formulas. Calculating the nominal life of ball and roller guides, you need to use different formulas.

With a constant stroke length and displacement frequency, the service life is expressed in time. With compact mounting dimensions, profile rail rails have a high load capacity. Installed in different types of machines or in other equipment, they are mounted in two different ways: in the form of a horizontal rail and a lateral installation method.

Since the configuration is carried out from two parallel rails, the location of the first rail is executed on the base side, and the other on the regulated side.

When working with large shock loads and vibrations, the installation of additional lateral parts - the side pressure plate, the set screws, the conical wedge - helps to eliminate them.

Installation of additional clamping parts when working with low load and low speeds of movement is not necessary.

Linear guides for CNC machines

What constitutes a linear displacement system? This is a combination of transmission and linear guides.

Linear guides for CNC are linear bearings, guide bushings, shafts. The guides themselves must solve three main tasks:

• Be a support for the acquisition of the machine;
• With minimum friction, to ensure the movement of machine components with the necessary accuracy along a given trajectory;
• To accept the loads arising during the work process.

Linear guides are divided according to the method of attachment to the machine. These guides, providing full support - the method of fastening to the bed along the entire length of the rails, and partial support - the method of end fastening.

Guides with full support have a large load capacity, in contrast to guides with partial support. Sometimes there are options when linear axes are set on the axes - both with full and partial fixation.

Representatives of this group are linear cylindrical guides. They realize the possibility of using several types of cylindrical guides:

• Guide polished shafts - is the most common (high availability, easy to install);
• Splined shafts - high wear resistance and rigidity, the ability to take torsional forces from the bushing. Used for the final installation of guides;
• The shafts on the support are cylindrical rails. They are used as a direct attachment to the machine.

Accuracy of the mounting surface

The profile rail guides are installed by fastening to the treated base surface. The method of fastening consists in creating a bead on the landing surface at the formation of a base surface or carriage on it. Elimination of misalignment is possible if there is a groove in the corner of the shoulder itself.

There is a direct relationship between the accuracy of the rail surface and the accuracy of the displacement. The accuracy of all equipment will depend on this. In this case, the accuracy of the machined mounting surface necessarily corresponds to the specified accuracy of movement. It is important to remember that it is necessary to take into account the flatness of the block, excluding the deformation of the carriage.

Base surfaces

To ensure an accurate and simpler installation, it is necessary to create basic surfaces that must be placed on the carriage and on the rail on one side.

The label should be on the opposite side. If sufficient accuracy is not ensured in view of the features of the wiring diagram, then the base surfaces are also processed on the second side.

Protection against corrosion and grease

To protect the guides from corrosion, they are made of stainless steel. There is a variant with a special protective coating. Its application is carried out if necessary in a high degree of protection against corrosion.

Finished factory guides are lubricated with grease, made on the basis of lithium soap. After that, they can be used for their intended purpose. Different operating conditions will require the desired periodicity of adding the same type of lubricant.