1. Calendering is a process in which material is subjected to stretching and deformation. The primary equipment used for calendering is a three-roll or four-roll calender. In a three-roll calender, this is achieved by the pressure exerted between two rotating rolls. As the rubber compound passes through the nip between the rolls, it is stretched under pressure into a strip of a specific cross-sectional shape, or it is applied as a coating onto fabric. This process is commonly employed for sheeting and shaping rubber compounds, applying adhesive coatings to textiles and steel‑cord fabrics, rubbing adhesives onto substrates, and laminating rubber sheets to one another or to coated fabrics.

The calendering process comprises the following basic operations: preheating and feeding of the compounded rubber; unwinding and drying of the textile fabric (sometimes followed by impregnation); calendering the rubber compound into sheets on a four-roll or three-roll calender, or applying the rubber to the textile fabric; and cooling, winding, cutting, and stacking the calendered semi‑finished products.

Prior to calendering, both the rubber compound and the textile fabric must undergo preliminary processing. Before entering the calender, the rubber compound is first passed through a mixing mill for re‑mixing; this step is referred to as “hot mixing” or “preheating.” Its purpose is to enhance the uniformity of the compound’s blending, further improve its plasticity, raise its temperature, and increase its workability. To improve the adhesion between the rubber compound and the textile fabric, the fabric should be dried to maintain a moisture content of 1%–2%. If the moisture level is too low, the fabric becomes brittle and prone to damage during calendering; if it is too high, its adhesive strength will be insufficient.

2. Extrusion molding, also known as die‑extrusion molding, is typically carried out using an rubber extruder, whose operating principle is similar to that of a plastic extruder. The material enters the barrel through the hopper and, under the action of the barrel and the rotating screw, is simultaneously heated and plasticized while being conveyed forward by the screw. It then passes continuously through the die head and, with the aid of a die, is shaped into products or semi‑finished articles of various complex cross‑sectional profiles, such as tire tread compounds, inner tube carcasses, solid rubber hoses, inner and outer layers of rubber hoses, and the sheathing of wires and cables.

3. Injection molding of rubber is a manufacturing process in which a compounded compound is directly injected from the barrel into a mold via a feeding device, similar to plastic injection molding. This method offers short cycle times, high production efficiency, reduced labor intensity, and superior product quality. It is primarily used for producing sealing rings, vibration‑damping pads, and footwear components.

The rubber injection molding process comprises feeding, plasticization, injection, pressure holding, vulcanization, and demolding. First, the pre‑compounded rubber compound is fed from the hopper into the barrel; under the rotation of the screw, it is conveyed along the helical grooves toward the front of the barrel. As it advances, vigorous mixing and deformation, combined with external heating of the barrel, rapidly raise its temperature and enhance its plasticity. Once the compound reaches the front of the barrel, the injection cylinder moves forward, bringing the nozzle at the barrel’s tip into contact with the mold’s gate. The injection cylinder then injects the rubber, which flows through the nozzle into the mold cavity, where pressure is held for a specified period. During this pressure‑holding phase, the rubber undergoes vulcanization at elevated temperatures until it is ready for demolding. The system then proceeds to the next injection cycle, repeating the sequence continuously.