The purpose and material selection of Guide strips

导向带的用途和材质选用

DMS Seals Technology Co., Limited specializes in the production of various types of seals and has extensive experience in the design, production and use of seals. Customers often ask about the performance and use of seals. Let me introduce them to you now.

What are Guide strips:

        Guide strips are strips that guide moving parts. Its main function is guidance. In order to realize this function of guidance, it must support the guided part and guide and correct its movement trajectory. In order to realize the function of the guide well, it also requires isolation, shock absorption and noise reduction of the guide parts.

Guide strips are mainly used in oil cylinders and cylinders. Due to their excellent performance, they are also widely used in other motion mechanisms.

1. Main requirements:

1）Support and positioning: Provide radial support and motion positioning to the piston and piston rod in the cylinder barrel.

2） Isolation: Isolate the two pairs of moving pairs, the piston and the cylinder barrel, the piston rod and the guide sleeve, to prevent direct scratches, wear and strain between the moving pairs. Especially when the moving pairs are all made of steel, they must be isolated, otherwise they will be easily injured.

3） Friction reduction: Guide strips also play an important role in reducing friction and friction work between moving parts, reducing ineffective work and heat.

4） Vibration absorption and noise reduction to reduce system operation vibration and noise

2. Materials:

        It is mainly filled with tetrafluoroethylene and phenolic cloth, and a very small amount of polyformaldehyde, nylon and soft metal are also used.

3. Use:

        Supplied in roll or split ring form. The open ring shape can be installed and used directly. The roll shape must be cut when used. The cutting length must be calculated in advance: there can only be one opening. The opening form is a 45° inclined opening. The opening distance is about 3-15mm, or the diameter of the guide ring. 3-5%.

        Generally, the openings are inclined openings. Straight openings or Z-shaped openings are rare, and they all have specific uses and purposes. The purpose of the opening is two-fold. First, it is to facilitate installation. If there is no opening, it will be a whole ring, which is difficult or impossible to install, so the opening must be made. Secondly, the opening should be opened with a certain opening distance to facilitate the automatic coordination of volume changes. Otherwise, the movement may be stuck or the moving parts may be strained due to excessive volume expansion of the guide strip under certain conditions. Rolled ones are relatively cheap, and the same rolled material can be used to make guide rings of different sizes.

（1） Phenolic cloth is generally in the shape of an open ring, and a small amount is in the shape of a roll.

（2）PTFE is generally in roll shape, and a small amount is in open ring shape.

4. Production method:

        Extrusion method (low cost, large batch size) and cutting and shaping method (high cost, small batch size, flexible production, many styles)

5. Carrying capacity:

        Varies depending on the hardness of the material. The general phenolic cloth is hard and has a large load-bearing capacity, while the PTFE-filled cloth is softer and has a smaller load-bearing capacity.

6. Operating temperature:

        Generally, the operating temperature range of phenolic cloth is -40 ~ 120 ℃. Those filled with PTFE can be used at -200~200℃, but the load-bearing capacity decreases as the temperature increases.

7. Life span:

        Phenolic cloth guide strips are prone to physical aging at higher temperatures (greater than 80°C) and in certain working media. The material gradually becomes hard and brittle, and finally cracks and scratches the working surface. Teflon guide tape does not have similar problems.

8. Friction coefficient:

        The dry friction coefficient between PTFE guide strip and steel is 2-10%, and the wet friction coefficient is 0.1-4%. The dry friction coefficient between phenolic cloth and steel is 20-40%, and the wet friction coefficient is 10-20%.

9. Media resistance:

        Teflon is resistant to all working media, while phenolic cloth is not resistant to working media containing water or brake oil.

10. Dirt holding capacity:

         The PTFE guide strip has excellent dirt-holding capacity and can block dirt in the working medium for the main seal and prevent damage to the main seal. Generally, when a phenolic cloth guide strip is installed, a tetrafluoroethylene guide strip must be installed, the purpose of which is to block dirt.

11. Running speed:

        The PTFE guide strip can be used in extremely high-speed or extremely low-speed cylinders. The phenolic cloth guide strip has a large friction coefficient, so the effect is not ideal at extremely high speeds or extremely low speeds.

12. Application:

       The phenolic cloth guide strip has strong load-bearing capacity. This guide strip must be installed for cylinders with large eccentric load, such as various heavy-duty cylinders, high-pressure cylinders, and large cylinders.

       The PTFE guide strip has a small friction coefficient and strong dirt-holding capacity. It is actually used in all types of oil cylinders, especially high-speed oil cylinders, high-efficiency, low-friction oil cylinders, and various engineering machinery oil cylinders.

13. Notes on use:

        Rolled guide strips are generally cut as needed before installation. When cutting, two issues need to be paid attention to: angle and length. The angle should be guaranteed to be around 45°, and the length should ensure that the opening size meets the standard.

        In a word, if the load capacity is the main consideration, it is recommended to give priority to phenolic cloth guide strips, and in all other cases, priority is given to filled PTFE guide strips.