Introduction to the selection of linear guides

one. Introduction of linear guide

Linear guides are also called slides, linear guides, and linear slides, which are used to support and guide the moving parts to make reciprocating linear motion in a given direction. Under the same volume of motion components, it has a higher rated load and motion accuracy than linear bearings, and can bear a certain torque load at the same time. As shown in Figures 1 and 2, linear guide rails can be used for heavy-duty handling in horizontal space, precise positioning movement and precise guiding movement in vertical space, realizing reliable movement in a small space. The robotics industry has a wider range of applications.

The linear guide is assembled by slide rails, sliders, balls, ball cages, ball-return grooves, etc. The main principle is to make the steel balls circulate through the structure of the ball-return grooves, ball cages, etc., so as to achieve Low-friction linear movement of the slider on the slide rail. This structure determines that the linear guide has the following basic characteristics:

Feature 1: Because it is a point-to-surface contact, the frictional resistance is small, and fine motion can be performed to achieve high-precision positioning of the control device.

Feature 2: Because the ball has its own rolling groove, the force on the rotating surface will be dispersed, so there is a larger allowable load.

Feature 3: Linear guides are not easy to generate frictional heat during operation, and are not easy to be deformed by heat, so they are suitable for high-speed motion.

Feature 4: Usually the contact angle of each ball row is 45°, so that the 4 acting directions (radial, reverse radial and lateral) on the slider all have the same rated load.


Figure 3 Schematic diagram of linear guide rail structure

two. Classification of linear guides

Misumi can provide a wide variety of linear guides suitable for various application scenarios. According to the applicable load, it can be divided into miniature, medium and heavy load. Linear guides are mainly loaded by balls, so the difference between miniature and medium and heavy-duty types is mainly the number of rows of balls. As shown in Figures 5 and 6, the miniature linear guide generally has 2 rows of steel balls, which are in contact with the track surface at 4 points, and the structure is compact; the medium and heavy-duty linear guides generally have 4 rows of steel balls, which improves the carrying capacity. Generally, the basic dynamic load rating of miniature linear guides is within 10KN, and the basic dynamic load rating of medium and heavy-duty types can be as high as 80KN.

Figure 5 Mini linear guide

Figure 6 Medium and heavy-duty linear guide

Misumi linear guides are classified as follows according to the width of the track and the width and length of the slider:

Widened rail use occasions:

The ratio of the total height of the standard rail to the width of the track is about 1.1, while the aspect ratio of the widened track is about 0.65. Compared with the standard track, the total height of the widened track is reduced by 40%. Therefore, it is most suitable for use in the occasions where the height direction is limited. Widen the track; on the contrary, when there is a limit in the width direction, please use the standard track.

On the other hand, the aspect ratio of the widened track is reduced. Compared with the standard track, the static allowable moment is increased by more than twice, and the rigidity is greatly improved. It is most suitable for the structure of the center of gravity shift.

Use occasions of widened slider:

The widened slider and the standard slider are roughly the same in terms of basic rated load and static allowable moment, and there is no change, but the fixing bolts on the widened slider are larger than the standard slider, and the fixing strength is improved.

Use occasions of various length sliders:

After selecting the track, what length of the slider to use, the main consideration is that the longer the slider, the greater the basic rated load and static allowable moment.