Manufacturing Process of Extruded Rubber Seals (Rubber Tubes, Rubber Cords, and Custom Profile Rubber Seals)

Extruded rubber seals are essential components widely used in automotive, construction, HVAC, and industrial machinery sectors, serving critical functions such as sealing, damping, and protection. This category includes three core products: rubber tubes (for fluid transfer), rubber cords (for gasketing and binding), and custom profile rubber seals (tailored to unique equipment geometries). Renqiu Aochen, leveraging advanced extrusion technologies and strict quality control, delivers extruded rubber seals with consistent dimensions, excellent sealing performance, and superior durability. Below is a detailed, step-by-step breakdown of the manufacturing process, highlighting Aochen's expertise in meeting diverse industrial requirements.

2.1 Custom Requirement Analysis & Material Formulation

The production of extruded rubber seals begins with in-depth collaboration between Aochen's technical team and customers to clarify key requirements. For rubber tubes, parameters such as inner/outer diameter, wall thickness, pressure-bearing capacity, and compatibility with conveyed fluids (oil, water, chemicals) are confirmed. For rubber cords, diameter tolerance, tensile strength, and application environment (temperature range, UV exposure) are defined. For custom profile rubber seals, detailed drawings or samples are analyzed to determine the cross-sectional shape, size, and functional demands (e.g., weather resistance, abrasion resistance). Based on these requirements, Aochen's R&D team formulates the optimal rubber compound: common base rubbers include EPDM (for weather resistance), NBR (for oil resistance), silicone (for high/low temperature resistance), and SBR (for cost-effective general applications). Functional additives such as anti-aging agents, plasticizers, and reinforcing fillers are precisely measured and mixed to enhance the compound's performance, ensuring it meets the specific needs of the extruded product.

2.2 Rubber Compound Preparation (Mixing & Kneading)

High-quality extruded rubber seals rely on homogeneous rubber compounds, and Aochen achieves this through its advanced intelligent rubber mixing production lines. First, raw rubber (e.g., EPDM, NBR) is softened and cut into manageable chunks. Then, pre-measured additives (fillers, anti-aging agents, vulcanizing agents) are added to the internal mixer. The mixing process is conducted at controlled temperatures (100-140°C) and speeds to ensure uniform dispersion of additives, transforming the raw materials into a primary rubber compound. The primary compound is then transferred to open mills for kneading and refining, which further reduces particle size, eliminates lumps, and adjusts the compound's viscosity to meet extrusion requirements. Aochen's intelligent mixing system monitors critical parameters in real-time-including temperature, mixing time, and torque-to avoid over-mixing (which degrades rubber properties) or under-mixing (which causes performance inconsistencies).

2.3 Preheating & Extrusion Molding

Preheating is a crucial pre-extrusion step to optimize the rubber compound's flowability. The refined rubber compound is fed into a preheater, where it is heated to a temperature of 60-80°C (varies by rubber type). This softens the compound, reducing extrusion resistance and ensuring smooth, continuous molding. The preheated compound is then fed into a screw extruder, the core equipment for extrusion molding. Aochen uses single-screw or twin-screw extruders based on product complexity and production volume: twin-screw extruders are preferred for high-volume or high-precision products due to their better mixing and conveying performance.

The extrusion process varies slightly by product type:

Rubber Tubes: The rubber compound is pushed through a die with a mandrel (internal core) to form the tube's inner and outer diameter. The mandrel ensures the inner cavity's uniformity, while the die determines the outer diameter. Aochen's precision dies are machined to tight tolerances (±0.1mm) to guarantee consistent tube dimensions.

Rubber Cords: The compound is extruded through a circular die of the desired diameter. For multi-strand or braided rubber cords, multiple extruders may be used to form the strands, which are then braided together post-extrusion.

Custom Profile Rubber Seals: The compound is extruded through a custom-shaped die (e.g., U-shape, O-shape, D-shape, or irregular profiles) designed to match the customer's specifications. Aochen's die-making team uses CAD/CAM technology to fabricate high-precision dies, ensuring the extruded profile matches the design exactly.

During extrusion, the screw speed, extrusion pressure, and die temperature are strictly controlled via computerized systems to maintain stable product dimensions and surface quality.

2.4 Continuous Vulcanization (Curing)

Unlike molded rubber parts that use batch vulcanization, extruded rubber seals require continuous vulcanization to maintain their continuous length. Aochen employs three primary continuous vulcanization methods based on rubber type and product requirements:

Hot Air Vulcanization (HAV): Suitable for most general-purpose rubbers (e.g., SBR, NBR). The extruded rubber product is conveyed through a heated oven (temperature: 150-200°C) at a controlled speed. The oven's temperature is evenly distributed to ensure uniform curing, enhancing the product's tensile strength and elasticity.

Steam Vulcanization: Used for high-performance rubbers (e.g., EPDM). The extruded product is passed through a steam chamber, where high-temperature steam (160-180°C) and pressure accelerate the vulcanization process. This method ensures deep, uniform curing, improving the product's resistance to heat and chemicals.

Gamma Ray Vulcanization: Applied for thin-walled or high-precision extruded products (e.g., small-diameter rubber tubes). This advanced method uses gamma rays to initiate cross-linking, resulting in faster curing, tighter dimensional control, and no surface discoloration.

Vulcanization is a critical stage that transforms the soft, plastic extrudate into a tough, elastic material with permanent shape and sealing properties. The vulcanization time and temperature are precisely calibrated to avoid under-curing (poor performance) or over-curing (brittleness).

2.5 Cooling & Sizing

After vulcanization, the hot extruded rubber product is immediately cooled to stabilize its dimensions and prevent deformation. Aochen uses air cooling or water cooling (via a cooling tank) for this purpose. Water cooling is faster and more effective for thick-walled products (e.g., large-diameter rubber tubes), while air cooling is preferred for thin-walled or profile products to avoid surface water spots.

For products requiring strict dimensional control (e.g., custom profile seals, precision rubber tubes), a sizing step is added post-cooling. The product is passed through a sizing die or calibrated roller to fine-tune its dimensions, ensuring it meets the customer's tolerance requirements.

2.6 Cutting & Post-Processing

Once cooled and sized, the continuous extruded rubber product is cut into the desired lengths using automated cutting machines (e.g., circular saws, laser cutters). For rubber tubes and cords, common lengths include 10m, 20m, or custom lengths as requested. For custom profile rubber seals, cutting is done to match the equipment's assembly requirements (e.g., straight lengths, coiled lengths, or pre-cut segments).

Post-processing steps may include:

Deburring: Removing any burrs or excess material from the cut ends to ensure smooth, clean edges.

Surface Treatment: Applying coatings (e.g., anti-friction coatings, adhesive layers) to enhance the product's functionality or ease of installation.

Assembly: For complex sealing systems, assembling extruded profiles with metal inserts, fabric reinforcement, or other components.

2.7 Quality Inspection & Packaging

Aochen's strict quality control system ensures every extruded rubber seal meets international standards (ISO 9001/14001) and customer specifications. Inspectors conduct comprehensive tests, including:

Dimensional Inspection: Using calipers, micrometers, or coordinate measuring machines (CMMs) to check diameter, wall thickness, profile dimensions, and length tolerance.

Performance Testing: Conducting tensile strength tests, elongation tests, compression set tests, and chemical resistance tests to verify the product's performance.

Visual Inspection: Checking for surface defects such as cracks, bubbles, unevenness, or discoloration.

Qualified products are packaged according to their type and customer requirements: rubber tubes and cords are often coiled and wrapped in moisture-proof film, while custom profile seals are placed in separate compartments or boxes to prevent deformation. Each package is labeled with product information (material, size, batch number) for traceability. Aochen's extruded rubber seals are shipped to global markets, providing reliable sealing solutions for automotive door seals, HVAC duct seals, industrial fluid transfer systems, and more.

Do you have new project plans or rubber product requirements? Feel free to contact Aochen anytime-our team is prepared to offer customized product solutions and competitive quotes. If you plan to participate in the Canton Fair next year, we will exhibit our best-selling rubber products, including industrial rubber sheets, rubber mats, and indoor sports flooring. We look forward to meeting you on-site for in-depth discussions and cooperation!

For more information about Aochen's products and manufacturing capabilities, visit our official website: www.aochenrubber.com.