67/22 Parallel Twin Screw Barrel

67/22 Parallel Twin Screw Barrel: High Performance Extrusion Component

Introduction

The 67/22 parallel twin screw barrel is a precision extrusion component with two screws rotating side by side. Designed for large-scale plastic processing, it provides consistent high output and superior mixing. With a screw diameter of 67 mm and a 22 L/D (length-to-diameter) ratio, this barrel supports high efficiency in demanding extrusion lines.

The parallel arrangement forces the material to pass between the intermeshing screws, ensuring homogeneous melting and continuous operation. Its robust structure allows it to handle challenging tasks with additives and fillers, making it ideal for high-quality PVC profiles, pipes, sheets, and wood-plastic composites.

🛠️ Technical Specifications Table

Design and Quality

• This twin screw barrel is made from high-quality alloy steel (such as nitrided 38CrMoAl) with a bimetallic structure for durability.

• Both screws maintain the same diameter along their lengths to ensure consistent flow.

• Advanced heat treatment (hardening, tempering, nitriding) creates a hardened surface layer (HRC ~56–58) and a strong alloy core (HRC ~56–64).

• The barrel is typically made in separate bolted halves, facilitating assembly and cleaning.

• Many barrels include interchangeable liner segments and modular screw sections.

• This modular design allows screw blocks (for feeding, compression, mixing, etc.) to be changed to accommodate different materials and reduce maintenance time.

• High-quality surface coatings (e.g., nickel or tungsten carbide) further enhance wear and corrosion resistance.

• Overall, precision machining and robust materials ensure long service life and consistent extrusion performance.

Applications

• Parallel twin screw barrels like the 67/22 are widely used in the plastic industry for the continuous extrusion of profile and pipe products.

• Typical applications include PVC and WPC flooring, PVC wall panels, rigid and flexible PVC profiles, and composite sheets.

• They are also used in the processing of filled plastics (e.g., PVC with CaCO₃) and engineering polymers (PP, PE, ABS).

• The twin screw design makes it suitable for handling high filler content and recycled materials, making it ideal for wood-plastic composites, pelletizing, and compound lines.

• Industries benefiting from this include construction, automotive, and packaging, where consistent product quality is critical.

• In these processes, the parallel twin screw barrel provides excellent mixing and gas venting, resulting in transparent, uniform sheets or dense pipes without lines or weak points.

Performance and Advantages

• Homogeneous Mixing: The twin screws intermesh to create strong shear forces, breaking up clumps and evenly distributing additives. This results in a homogeneous melt with consistent properties. Studies show that intermeshing twin screws provide superior mixing compared to single screws.

• High Efficiency: The 67/22 twin screw setup provides higher throughput under the same operating conditions. A larger combined flight area and improved pumping action push more material through the barrel. This increases production rates (typically above 100 kg/hour for PVC) while maintaining quality. In practice, as long as the screw design and speed are optimized, increasing throughput improves mixing homogeneity and particle distribution.

• Improved Quality: Consistent residence time and melting ensure that each part of the melt experiences the same thermal history. The result is more homogeneous color, density, and fewer defects. High intermeshing efficiency also balances pressure and minimizes fluctuations. Consequently, this design reduces scrap and downtime.

• Durability: Hard materials and surface treatments give the barrel high wear resistance. Nitrided steel and bimetallic liners are resistant to wear from fillers and regrind. The design typically includes robust bearings and easy cooling, keeping temperatures stable under high loads. Overall, the 67/22 twin screw barrel offers a reliable, long-lasting solution for heavy-duty extrusion.

Operation and Maintenance

• Parallel twin screw barrels are designed for ease of use and maintenance.

• The split barrel structure (upper and lower halves) provides quick access for inspection and cleaning.

• Each screw and barrel segment can be removed individually.

• Regular lubrication of bearings and drives ensures smooth rotation; the barrel typically needs to be cooled with water or air to control temperature.

• Wear parts (screw tips, mixing elements, liners) can be replaced in sections, reducing downtime.

• For example, worn kneading blocks or screw flights can be renewed without replacing the entire screw.

• Deep nitriding (0.5–0.8 mm case depth) and low roughness (Ra ~0.4 μm) help minimize wear, but routine inspection is recommended.

• Cleaning is easy: bolts are loosened to open the barrel, screws are retracted, and the interiors are cleaned.

• This self-cleaning, modular design ensures reliable operation of the extruder and reduces labor between production runs.