Detailed Explanation of the Complete Production Process of Rubber O-Rings

The core process of rubber O-ring production is as follows: mixing → molding (compression molding / injection molding) → vulcanization → post-treatment → inspection. Among them, vulcanization cross-linking is the key step that determines the physical properties.

1. Raw material preparation and mixing
   • Formula design: Select the appropriate raw rubber (such as NBR for oil resistance, FKM for high-temperature resistance, VMQ for wide temperature resistance) based on the working conditions, and add vulcanizing agents, accelerators, reinforcing agents (carbon black), antioxidants, etc.
   • Intensive mixing and plasticizing: The raw rubber is mixed and kneaded in a high-temperature extruder to ensure the uniform dispersion of the additives; some natural rubber may need to be pre-plasticized to reduce viscosity.
   • Sheet production and storage: The mixed rubber is extruded through an extruder, cooled, and then stored for 4-8 hours to eliminate internal stress and stabilize the formulation structure.
2. Semi-finished product preparation and molding
   • Gel sheet cutting: Precisely cut the rubber strips or blocks according to the theoretical weight of the O-ring, with an error controlled within ±1% to prevent insufficient rubber or excessive flying edges.
   • Molding methods:
   • Compression molding: Place the rubber sheet manually or automatically into a closed mold, suitable for small batches, large sizes, or special materials, with lower efficiency but greater flexibility.
   • Injection molding: Heat the rubber sheet and melt it under high pressure before injecting it into a multi-cavity mold, suitable for large batches, small sizes, with high dimensional accuracy and less waste.
3. Vulcanization process (core)
   • Hot vulcanization: Conducted in a flat vulcanization machine or injection press, with a temperature of typically 150-180°C, pressure of 10-30 MPa, and time of 10-30 minutes (adjustable according to the thickness and type of the rubber).
   • Reaction mechanism: Under high temperature and high pressure, the vulcanizing agent initiates the cross-linking of rubber molecules, transforming the plastic material into an elastic material, establishing key indicators such as tensile strength, compression permanent deformation, etc.
   • Parameter control: Temperature fluctuations should be within ±2°C to avoid over-vulcanization (too early vulcanization) or insufficient vulcanization.
4. Post-processing procedures
   • Deburring (trimming): After vulcanization, the product has edge defects at the parting surface, which can be removed by freezing trimming (low-temperature brittleness removal) or manual/automatic trimming to ensure a round cross-section.
   • Secondary vulcanization (post-heating): Some high-performance rubber materials (such as FKM, VMQ) need to undergo secondary vulcanization in an oven at around 200°C for several hours to remove low-molecular volatile substances, reduce compression permanent deformation, and improve heat resistance stability.
   • Cleaning and surface treatment: Clean the residual release agent with water, and apply silicone oil or lubricant as necessary to prevent adhesion.
5. Quality inspection and packaging
   • Overall appearance inspection: Check for bubbles, impurities, cracks, missing rubber, and residual edge defects.
   • Size inspection sampling: Measure the inner diameter, wire diameter, and roundness according to GB/T 3452.1 or AS568 standards.
   • Performance testing: Regularly sample for hardness, tensile strength, elongation at break, compression permanent deformation, and medium resistance tests.
   • Packaging and storage: Qualified products are packaged in a light-protected, low-temperature, and dry environment to avoid deformation under pressure, with the batch number noted for traceability.