Full definition
Rubber extrusion is a continuous manufacturing process that allows for the production of rubber profiles with a constant cross-section. In this process, compounded rubber is forced through a precisely shaped die, resulting in products that can be produced at impressive rates ranging from 5 to over 100 meters per minute. The extrusion system typically consists of a screw with a diameter ranging from 60 to 250 mm, which rotates within a heated barrel. This setup feeds rubber through a die head where the desired shape is formed. Following extrusion, the rubber undergoes a curing process, often referred to as vulcanization, which can take place in a variety of environments, including hot-air tunnels, microwave ovens, salt baths, liquid curing mediums (LCM), or steam autoclaves. The choice of curing method can significantly influence the physical properties of the final product.
Rubber extrusion is utilized to manufacture a wide range of products including sealing profiles (such as P, D, E, U, J shapes, and custom cross-sections), hoses (either mandrel or mandrel-less), cord with a round cross-section, tubing, and weatherstrips. Common materials used in the extrusion process include EPDM, which is the most prevalent choice for weatherstrips and seals due to its excellent weather resistance; silicone, often used for medical tubing and oven seals; neoprene, known for its fuel resistance; and NBR, which is typically used for oil-resistant hoses. Dimensional tolerances of ±0.15-0.30 mm on critical dimensions are standard in the industry, ensuring that the extruded products meet specific application requirements.
One of the critical aspects of rubber extrusion is die design. Upon exiting the die, rubber swells by approximately 5-30%, a phenomenon known as die swell. This characteristic necessitates careful compensation in the die geometry to ensure the final product dimensions are accurate. Additionally, maintaining quality during the extrusion process is paramount; techniques such as continuous laser scanning of the profile dimensions are employed to ensure that the extruded profiles meet the required specifications consistently. This rigorous quality control is essential in industries where precision and reliability are critical, such as automotive, aerospace, and medical applications.