The production of PTFE bellows requires fine control throughout the entire process. The core stages include raw material pretreatment, forming, post-processing, and quality inspection. Different forming processes are suited for different application scenarios.

Raw Material Pretreatment

Raw material pretreatment is the foundation for quality assurance. It involves selecting PTFE resin with a purity of ≥99.9%, mixing it with lubricant additives in a specific ratio, and allowing it to stand for pre-forming. The mixture is then cold-press extruded into a fibrous pre-form, which is subsequently dried to remove the additives. For special properties, modified components such as anti-static masterbatches or carbon fibers can be incorporated, ensuring they are uniformly dispersed.

Forming

Forming is the core stage, with three mainstream processes:

1. Inflation Forming: A pre-formed tube is placed into a mold and heated to 275°C-285°C. Internal pressure is applied to make the tube conform to the mold's corrugated shape. After cooling and setting, it is demolded. This method is suitable for shapes like U-type and spiral corrugations, allows for flanging to connect flanges, complies with the GB-2555~81 standard, and is currently the most widely used process.

   
   

2. Stretching Forming: The material is stretched at high speed below the PTFE melting point, followed by high-temperature heat setting to form an expanded PTFE base film. This film is then reheated and pressurized to fuse and stabilize its porous network structure.

   
   

3. Spiral Corrugation Forming: This process is suitable for applications with high fatigue performance requirements (≥1000 bending cycles). A thin-walled tube is heated and rotated to form the corrugations, with the ends specially treated to restore their shape.

Post-processing

Post-processing is used to optimize performance and precision. It includes:

• Sintering and Setting: Performed via static pressure sintering, where the temperature is raised above the melting point and held to stabilize the material's structure.

  
  

• Machining: Lathe machining is used, controlling rotation speed and feed rate to precisely machine flange interfaces.

  
  

• Sealing and Reinforcement Treatment: The sealing surface can be optimized by filling with PTFE, or pressure resistance can be enhanced using a metal mesh and glass fiber composite structure, achieving a maximum pressure resistance of up to 1MPa.

  
  

Quality Inspection

Quality inspection runs through the entire production process. Core tests include hydrostatic testing, air-tightness testing, corrosion resistance testing (with an annual corrosion rate of <0.01mm), ring stiffness testing (per QB/T 1916-93), fatigue testing, and dimensional accuracy testing. These ensure the product meets industry standards and avoids defects such as bubbles, cracks, and leaks.