The EPDM rubber sealing strip production line uses a cold-feed extruder/vulcanization tunnel.

Here is a detailed breakdown of a typical EPDM Rubber Sealing Strip Production Line based on a Cold-Feed Extruder and Vulcanization Tunnel system.

This line is designed to produce continuous lengths of precisely shaped, dense, and vulcanized EPDM rubber seals for automotive, construction, appliance, and industrial applications.

Core Principle: A shaped die (the "head") is fitted to the end of an extruder. The unvulcanized EPDM compound is forced through this die to create a continuous profile, which is then cured in a continuous vulcanization tunnel.

• Internal Mixer (Banbury) & Two-Roll Mill: Raw EPDM, carbon black (for black strips), fillers, oils, vulcanizing agents, and pigments (for colored strips) are compounded into a homogeneous, sheeted rubber compound.

• Strip Feeder / Pre-former: The compound is often cut into continuous strips or "ropes" that serve as the consistent feed for the cold-feed extruder. This ensures steady pressure and a void-free extrudate.

• Cold-Feed Extruder: Unlike a hot-feed extruder, this unit accepts the unheated, room-temperature rubber strip. It has a longer barrel (higher L/D ratio) with precisely controlled heating/cooling zones.

  • The screw shear-heats and plastifies the rubber as it conveys it forward.

  • Key advantage: Better temperature control, mixing, and suitability for modern, faster-curing compounds.

• Extrusion Head & Profile Die: This is the tooling that defines the final shape of the sealing strip (e.g., door seal, glass run channel, bulb seal, sponge seal).

  • The die is meticulously machined from hardened steel.

  • Design is critical to account for "die swell" – the tendency of the elastic rubber compound to expand after exiting the die.

This is where the shaped, soft rubber profile is permanently cured into its final elastic form.

• Types of CV Tunnels:

  • Hot Air Vulcanization (HAV) Tunnel: The most common method for dense EPDM seals. The profile passes through a multi-zone oven with precisely controlled, circulating hot air (typically 180°C - 250°C). The length and temperature determine the cure time.

  • Microwave (UHF) + Hot Air Hybrid Tunnel: Very common and efficient for EPDM. The microwave energy heats the rubber internally and instantly, while subsequent hot air zones complete the cure and control surface finish. This allows for higher line speeds.

  • Salt Bath (LCM) or Liquid Curing Medium: Less common for EPDM seals today due to environmental and cleaning concerns, though very efficient.

• Cooling Trough: A long water bath or misting chamber that rapidly cools the vulcanized profile, stopping the chemical reaction and setting its properties.

• Laser / Optical Profile Scanner: Critical for quality control. Continuously measures the strip's dimensions against the CAD drawing tolerance in real-time.

• Caterpillar Haul-Off / Puller: Provides the constant, tension-controlled pulling force that drives the entire continuous line, synchronizing speed from extruder to cutter.

• Cutting / Spooling Unit:

  • Flying Knife Cutter: For cutting strips to precise lengths (e.g., for automotive door seals).

  • Coiling or Spooling Station: Winds continuous lengths onto reels or spools for bulk shipping (e.g., for construction weather-stripping).

• Surface Treatment (Optional): Some lines include a station to apply a silicone-based lubricant or flocking (adhesive + fine fibers) to the seal surface immediately before spooling.

• Compound Rheology: The flow characteristics of the EPDM compound must be perfectly matched to the die design and vulcanization speed to prevent defects (sharkskin, tearing, porosity).

• Die Design & Compensation: This is an art and science. The die orifice is not the final shape; it is engineered to deform predictably as the rubber swells and sags after exiting.

• Vulcanization Profile: The temperature-time profile in the CV tunnel must ensure the thickest section of the profile is fully cured without scorching (premature vulcanization) the thinner sections.

• Dimensional Stability & Tolerances: Automotive and architectural applications demand extremely tight tolerances (±0.2mm). Real-time laser scanning is essential.

• Surface Finish: The tunnel atmosphere and temperature must produce a smooth, non-porous, and consistent surface.

The Cold-Feed Extruder/Vulcanization Tunnel line is the industry-standard, high-efficiency method for producing high-quality, continuous EPDM sealing profiles. It is a continuous, automated process where precision in compound formulation, die design, and vulcanization control directly translates to the performance, durability, and fit of the final seal. This technology is fundamentally different from the batch/semi-continuous, size-reduction-focused process used for sports granules.