Do you know how many types of guide rails are there in CNC machining centers?

“Detailed Explanation of Guide Rail Types for CNC Machining Centers”

1. Linear Motion Guide Rail
   The linear motion guide rail is the most common guide rail type in machining centers. It guides the moving parts to move precisely in a straight line. Linear motion guide rails have the advantages of simple structure, easy manufacturing, and easy guarantee of accuracy. On each axis of the machining center, such as the X-axis, Y-axis, and Z-axis, linear motion guide rails are usually used.
   The accuracy and performance of linear motion guide rails depend on the material, manufacturing process, and installation accuracy of the guide rails. High-quality linear motion guide rails can ensure stable accuracy and reliability of the machining center under high-speed movement and heavy load conditions.
2. Circular Motion Guide Rail
   Circular motion guide rails are mainly used for the rotating shafts of machining centers or components that need circular motion. The design and manufacturing of circular motion guide rails are relatively complex, and factors such as centrifugal force and friction need to be considered due to the particularity of circular motion.
   Circular motion guide rails usually use high-precision ball or roller bearings to ensure the smoothness and accuracy of rotational motion. In some high-precision machining centers, hydrostatic circular motion guide rails are also used to further improve the accuracy and stability of the rotating shaft.

1. Main Motion Guide Rail
   The main motion guide rail is the guide rail responsible for realizing the main motion of the tool or workpiece in the machining center. The accuracy and performance of the main motion guide rail have a crucial impact on the machining accuracy and efficiency of the machining center.
   In machining centers, high-precision rolling guide rails or hydrostatic guide rails are usually used for the main motion guide rails. These guide rails have characteristics such as high speed, high accuracy, and high rigidity, and can meet the requirements of machining centers under high-speed cutting and heavy-load machining conditions.
2. Feed Motion Guide Rail
   The feed motion guide rail is the guide rail responsible for realizing the feed motion of the tool or workpiece in the machining center. The accuracy and stability of the feed motion guide rail directly affect the machining accuracy and surface quality of the machining center.
   Feed motion guide rails usually use sliding guide rails, rolling guide rails, or hydrostatic guide rails. Among them, rolling guide rails and hydrostatic guide rails have higher accuracy and stability and are suitable for high-precision machining centers; while sliding guide rails have the advantages of simple structure and low cost and are suitable for some medium and low-precision machining centers.
3. Adjustment Guide Rail
   The adjustment guide rail is the guide rail used in the machining center to adjust the position of the tool or workpiece. The accuracy and flexibility of the adjustment guide rail have an important impact on the machining accuracy and operational convenience of the machining center.
   Adjustment guide rails usually use sliding guide rails or rolling guide rails. These guide rails have a small friction coefficient and high accuracy and can easily realize fine adjustment of the tool or workpiece.

1. Sliding Guide Rail
   (1) Traditional Sliding Guide Rail
   Traditional cast iron-cast iron and cast iron-quenched steel guide rails have the advantages of simple structure, easy manufacturing, good rigidity, and high vibration resistance. However, this kind of guide rail has the disadvantages of a large static friction coefficient and a dynamic friction coefficient that changes with speed, resulting in large friction loss. At low speeds (1-60 mm/min), crawling phenomena are prone to occur, thus reducing the positioning accuracy of moving parts. Therefore, except for economic CNC machine tools, traditional sliding guide rails are no longer used on other CNC machine tools.
   (2) Plastic-Clad Sliding Guide Rail
   At present, most CNC machine tools use plastic-clad guide rails, that is, a plastic film soft belt composed of plastic and other chemical materials is pasted on the friction surface of the moving guide rail. Guide rail plastics are commonly divided into two types: Teflon guide rail soft belt and epoxy wear-resistant guide rail coating.
   Plastic-clad sliding guide rails have the following characteristics:
   • Good friction characteristics: The plastic film soft belt of the plastic-clad guide rail has a low friction coefficient, which can reduce the friction resistance of moving parts and improve the smoothness of movement.
   • Good wear resistance: The plastic film soft belt has good wear resistance and can extend the service life of the guide rail.
   • Stable movement: The friction coefficient of the plastic-clad guide rail is stable and does not change with speed. Therefore, the movement is stable and crawling phenomena are not easy to occur.
   • Good vibration damping: The plastic film soft belt has certain elasticity and can absorb the vibration of moving parts and improve the machining accuracy of the machining center.
   • Good manufacturability: The manufacturing process of plastic-clad guide rails is relatively simple, with low cost and easy installation and maintenance.
2. Rolling Guide Rail
   (1) Working Principle
   Rolling guide rails place rolling elements such as balls, rollers, and needles between the guide rail surfaces to turn the sliding friction between the guide rail surfaces into rolling friction. This friction method greatly reduces friction resistance and improves the sensitivity and accuracy of movement.
   (2) Advantages
   • High sensitivity: The difference between the dynamic friction coefficient and the static friction coefficient of rolling guide rails is very small, so the movement is stable and crawling phenomena are not easy to occur when moving at low speeds.
   • High positioning accuracy: The repeat positioning accuracy of rolling guide rails can reach 0.2 um, which can meet the requirements of high-precision machining centers.
   • Small friction resistance: The rolling friction coefficient of rolling elements is much smaller than the sliding friction coefficient, making the movement of moving parts lighter and reducing the consumption of driving power.
   • Small wear, good accuracy retention, and long service life: The contact area between rolling elements and guide rail surfaces is small, with little wear and can maintain high accuracy for a long time.
     (3) Disadvantages
     Rolling guide rails have poor vibration resistance and high protection requirements. During the machining process, vibration will affect the movement accuracy of rolling elements, thereby reducing the machining accuracy of the machining center. In addition, rolling guide rails require good protection measures to prevent dust, chips and other impurities from entering the guide rail surface and damaging the rolling elements and guide rails.
     (4) Application Occasions
     Rolling guide rails are particularly suitable for occasions where the working parts of machine tools require uniform movement, sensitive movement, and high positioning accuracy. This is the reason why rolling guide rails are widely used in CNC machine tools.
3. Hydrostatic Guide Rail
   (1) Liquid Hydrostatic Guide Rail
   • Working Principle
     There is an oil chamber between the two guide rail working surfaces of the liquid hydrostatic guide rail. After introducing lubricating oil with a certain pressure, a hydrostatic oil film can be formed, making the working surface of the guide rail in pure liquid friction without wear and with good accuracy retention.
   • Advantages
     • High accuracy: Liquid hydrostatic guide rails can provide extremely high accuracy and ensure stable accuracy of the machining center under high-speed movement and heavy load conditions.
     • Low friction coefficient: Pure liquid friction makes the friction coefficient extremely low, greatly reducing the consumption of driving power.
     • No crawling at low speeds: Even at low speeds, liquid hydrostatic guide rails do not exhibit crawling phenomena, ensuring the smoothness of movement.
     • Large carrying capacity and good rigidity: The hydrostatic oil film can withstand a large load, improving the carrying capacity and rigidity of the machining center.
     • The oil has a vibration absorption effect and good vibration resistance: The oil can absorb vibration and reduce the impact of vibration during machining on machining accuracy.
   • Disadvantages
     The structure of liquid hydrostatic guide rails is complex, requiring an oil supply system, and the cleanliness of the oil is required to be high. This increases the cost of manufacturing and maintenance.
   • Classification
     Liquid hydrostatic guide rails for machining centers can be divided into two major categories: open type and closed type. The oil chamber of an open liquid hydrostatic guide rail is directly connected to the outside world, with a simple structure but is prone to external pollution; the oil chamber of a closed liquid hydrostatic guide rail is closed, and the oil is recycled for use, with high cleanliness but a complex structure.
     (2) Gas Hydrostatic Guide Rail
   • Working Principle
     After introducing gas with a certain pressure between the two guide rail working surfaces of the air hydrostatic guide rail, a hydrostatic air film can be formed, making the two guide rail surfaces of the CNC punching machine evenly separated to obtain high-precision movement.
   • Advantages
     • Small friction coefficient: The friction coefficient of gas is extremely small, making the movement of moving parts lighter.
     • Not easy to cause heating and deformation: Due to the small friction coefficient, less heat is generated and it is not easy to cause heating and deformation of the guide rail.
   • Disadvantages
     • Small carrying capacity: The carrying capacity of gas hydrostatic guide rails is relatively small and is often used in occasions with small loads.
     • Air pressure fluctuations affect accuracy: Fluctuations in air pressure will cause changes in the air film, thereby affecting the accuracy of the guide rail.
     • Dust prevention must be noted: Dust falling into the air guide rail surface will cause damage to the guide rail surface, so effective dust prevention measures must be taken.