What is a Linear Guideway?

Figure 1: Linear guideways.

1. Definition

Linear guideway, also known as linear guide rail, slide rail, linear guide and linear slide rail, is used for high-precision or high-speed linear reciprocating motion. It can bear a certain torque and realize high-precision linear motion under high load.

2.Structure

Figure 2: Structure of a linear guideway

The rolling circulation system of linear guideway mainly consists of slider, ball retainer, end cover, slide rail and steel ball.

1.The slider is the main structure sliding on the guideway(Other parts such as end cover and steel ball are installed inside it).

2.The slide rail: the slide rail of linear guideway can be regarded as the "track of train". It mainly carries the sliding block to move back and forth. The common slide rail length is not fixed and can be customized according to the actual needs of customers.

3.The end cover: the end cover of linear guideway is generally made of metal and has strong heat resistance. The sealing performance of an end cover is directly related to whether foreign matters can be prevented from entering the guide rail.

4.The steel ball: the diameter of steel ball used for linear guideway of each specification and model is different. Generally, the diameter of different steel ball models varies by 2μm.

5.The steel ball holder: we can know from the name that it is an auxiliary accessory for holding steel balls. Generally, when manufacturing the guide rail, first turn the steel balls into the holder and then install the sliding block.

3. Working principle

The working process of linear guideway can be understood as a kind of rolling guidance, which is an infinite rolling cycle between the sliding block and the guide rail by steel balls, so that the load platform can easily carry out high-precision linear movement along the guide rail. It can reduce the friction coefficient to one fiftieth of the normal traditional sliding guidance and can easily achieve high positioning accuracy.

The final unit design between the sliding block and the guide rail makes the linear guideway bear the load in the up, down, left, right and other directions at the same time. The refined and simplified structural design makes the linear guideway move more smoothly and with low noise.

The design of the guide rail system strives to maximize the contact area between the fixed elements and the moving elements. It can not only improve the bearing capacity of the system, but also the system can withstand the impact force generated by intermittent cutting or gravity cutting. In addition, it can also widely spread the force and expand the bearing area.

In order to achieve this, the groove shapes of the guideway system are diverse and there are two representative ones. One is called Gothic (pointed arch), the shape is the extension of semicircle, and the contact point is the vertex. The other one is circular arc, which can also play the same role. No matter which structural form there is only one purpose, that is to strive for more rolling steel ball radius to contact with the guide rail (fixed elements). The factor that determines the performance characteristics of the system is how the rolling element contacts the guide rail, which is the key to the problem.

4. Classification

Figure 3: Different linear guideways

Linear guideway can be divided into Ball Type Linear guideway and Roller Type linear guideway. The speed of Ball Type linear guide is slow, but the precision is very high. So it is suitable for high-speed and light load.

The linear guideway is divided into Circular arc groove linear guideway and Gothic groove linear guideway according to the groove shape. The circular arc groove linear guideway is two-point contact, and the Gothic groove linear guideway is four point contact.

According to the contact form, it is divided into DF type and DB type. DF type guide rail can be self-aligning allowing more assembly errors. And DB type guide rail has high rigidity.

According to the nature of friction, the linear guideway can be divided into Sliding friction linear guideway, Rolling friction linear guideway, Elastic friction linear guideway, Fluid friction linear guideway and so on.

5. Function and Application

The function of linear guideway is to support and guide moving parts to make reciprocating linear motion in a given direction. When linear guideway is used in reciprocating motion, it will save workers' effort. Linear bearings are mainly used in automatic machinery, such as machine tools, bending machines, laser welding machines imported from Germany and so on. Of course, the linear bearing is matched with the linear shaft.

The linear guideway is also mainly used in mechanical structures with high precision requirements. A rolling steel ball is used instead of an intermediate medium between the moving element and the fixed element of the linear guide rail. Because the rolling steel ball is suitable for high-speed movement, small friction coefficient and high sensitivity. So it can meet the working requirements of moving parts, such as tool holder and carriage of machine tool.

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