1. Raw Rubber Mastication
　　Rubber processing techniques have certain requirements for the plasticity of raw rubber. To meet various process performance requirements, raw rubber must undergo mastication. However, the initial plasticity of most synthetic rubbers is controlled during synthesis, so they can be directly mixed without mastication. In addition, natural rubber, acrylonitrile butadiene rubber, isoprene rubber, and styrene-butadiene rubber all require moderate mastication.
　　Mastication can reduce the viscosity of rubber, making it easier to incorporate compounding agents; mastication can improve the rheological properties of rubber, reducing die swell and calender shrinkage; mastication can also improve the solubility and moldability of the rubber compound. Mastication must be moderate; excessive mastication will reduce the strength, elasticity, abrasion resistance, and aging resistance of the vulcanized rubber. Plasticity is mainly determined according to the process performance of the mixed rubber and the performance requirements of the product. Raw rubber mastication is generally carried out on an open mill, but it can also be carried out on a closed mill.
　　2. Compounding
　　Accurately weigh the raw rubber and various compounding agents according to the formula of the practical rubber compound.
　　3. Mixing
　　The process of combining various compounding agents with raw rubber on a mill to produce a mixed rubber compound is called mixing. Mixing is not simply a mechanical mixing process of raw rubber and compounding agents, but also a physicochemical process in which various components are infiltrated, dispersed, adsorbed, and combined to form a colloidal dispersion with a complex network structure. It is actually a rubber modification process.
　　In the entire rubber processing process, the quality of the mixed rubber has a decisive influence on the further processing of the rubber compound and the performance of the final product. Mixing is one of the processes most prone to quality fluctuations. If mixing is not good, the rubber compound will have uneven dispersion of compounding agents, fluctuations in plasticity, and even phenomena such as scorching and blooming, leading to a decrease in the performance of the vulcanized rubber and finished products.
　　Mixing can be carried out on an open mill or an internal mixer. For rubber compounds with small scale, small batches, and frequent changes in varieties, open mills are often used for mixing. In addition, open mills are also particularly suitable for the preparation of some special rubber compounds, such as sponge rubber, hard rubber, and nitrile rubber and fluorine rubber. Internal mixing is safer than open mill operation, the phenomenon of dust flying is significantly improved, the mixing process is mechanized, labor intensity is reduced, mixing time is shortened, and production efficiency is improved. The rubber compound mixed by the internal mixer must be left for 4-8 hours before further processing on an open mill, adding accelerators and vulcanizing agents.
　　4. Semi-finished Product Preparation
　　The production of O-ring rubber seals is generally still mainly based on the molding method. In order to improve production efficiency and product quality and reduce waste, pre-manufacturing semi-finished products is necessary. The traditional manufacturing process of flat vulcanized semi-finished products is that qualified mixed rubber is fully remilled and then pressed into sheets, cut into strips and blocks. For large-volume or large-specification products, it can be extruded into rubber cords according to the required specifications on an extruder, cut into a certain length, and the joints are overlapped at 45° to form O-ring semi-finished products. In recent years, many domestic manufacturers have adopted precision pre-forming machines to produce semi-finished products of O-rings and other products. This not only improves production efficiency but also ensures the accuracy of the volume and weight of semi-finished products, improving the level of rubber product production technology. When using an injection molding machine for production, semi-finished products do not require special preparation; only the pressed rubber strips need to be fed directly.
　　5. The final step is the vulcanization of the rubber seal ring