Rubber sealing strips are a very common product in our daily lives. During production, they are primarily formed by extrusion using a rubber extruder. Based on their structure, rubber sealing strips can be classified into single‑extrusion seals and composite seals. Single‑extrusion seals are manufactured by a single rubber extruder that shapes the product through extrusion. After extrusion, a conveyor belt transports the parts into a hot‑air curing oven for vulcanization, followed by water cooling to produce the desired single‑extrusion seal. Examples include sealing strips for architectural doors and windows, as well as those used in cabinets. In contrast, the sealing strips employed on automobile doors belong to the category of three‑component composite seals. These typically consist of foamed rubber, solid rubber, and a steel strip. During manufacturing, the steel strip is fed from a steel‑strip storage rack; it enters the composite die head, where it bonds with rubber extruded by two separate rubber extruders, forming the required seal structure. Each of the two extruders produces a different type of rubber, and the specific machine models are selected according to the proportion of each rubber component in the final product. Following extrusion, the parts undergo vulcanization in a hot‑air curing oven and are then cooled in a water‑cooling tank. However, after cooling, the products must still pass through punching machines, strip‑cutting equipment, and sealing‑strip forming machines before they are fully finished.

1. Operating Principle

Extrusion molding is a manufacturing process in which a plasticizable compound is continuously forced through a die under specific conditions, thereby producing a product with a defined cross-sectional shape.

As the rubber compound advances along the screw, mechanical and thermal effects cause changes in its viscosity and plasticity, transforming it into a viscous fluid. Based on the material’s behavior during extrusion, the working section of the screw is typically divided into three distinct zones—feeding, compression, and metering—each serving a different function.

2. Cold-feed extrusion

Advantages: It saves on hot‑melt processing equipment, facilitates mechanization and automation, and, thanks to the extruder’s enhanced screw shear and plasticizing action, ensures uniform temperature and plasticity of the compound. It also improves the quality of extruded products, enhances surface finish, and produces semi‑finished extrudates with more stable and consistent dimensions. Furthermore, cold‑feed extrusion is less sensitive to pressure fluctuations and offers greater operational flexibility, while requiring lower capital and operating costs.

3. Equipment Features

Suitable for extruding rubber compounds (EPDM, natural rubber, nitrile rubber, butyl rubber, and reclaimed rubber), it is used in the production of composite sealing strips for architectural doors and windows, single‑extruded sealing strips, as well as various dense and foamed rubber products—such as strip‑shaped, bar‑shaped, tubular, and sheet‑like items—for applications in construction, electrical appliances, machinery, water conservancy, and other industries.

Cold-feed rubber sealing strip extruder: This is a type of equipment that uses cold rubber for production, with forced cold feeding as the standard feeding method. Cold-feed rubber extruders are characterized by high production efficiency and stable operation. Extruders are commonly used to manufacture products such as sealing strips and rubber hoses that can be produced via extrusion. An extruder is a rubber‑processing machine employed to extrude tread compounds, inner tubes, rubber hoses, and various rubber profiles.

Hebei Shuangda Rubber & Plastics Machinery Co., Ltd. is a modern enterprise integrating research and development, manufacturing, and sales of complete sets of extrusion equipment for rubber, silicone, and plastics. The company’s main products include rubber extruders, rubber hose extrusion lines, three‑layer composite sealing strip extrusion lines, silicone sealing strip production lines, plastic sealing strip production lines, plastic profile production lines, plastic pipe production lines, elastomer extruders, and other extrusion equipment, as well as production machinery for engineering seals, automotive seals, wire and cable applications, air‑conditioning hoses, braided hoses, automotive hoses, waterstop strips, and related products.