125/30 Parallel Twin Screw Barrel

Executive Summary

The 125/30 Parallel Twin Screw Barrel is a precision-engineered extrusion component specifically designed for high-capacity plastic processing applications. With a 125 mm screw diameter and a 30:1 length-to-diameter (L/D) ratio, it offers an expanded plasticizing area for high output capacity.

Manufactured from high-strength 38CrMoAlA alloy steel with advanced surface treatments (nitriding, bimetallic coating), this barrel provides excellent wear and corrosion resistance. It is compatible with major twin-screw extruder brands (e.g., KraussMaffei 125-30 series, Bausano MD-125/30) and is ideal for the production of PVC/PE/PP pipes, profiles, sheets, and wood-plastic composites (WPC).

Introduction

Parallel twin screw barrels are critical components of co-rotating twin-screw extruders that provide balanced melting, strong mixing, and stable pressure during extrusion. The 125/30 barrel offers balanced compression and complete plasticization through two screws of the same diameter working side by side within a split barrel. This design is commonly used in large extrusion lines (PVC pipes, PE/ABS profiles, WPC sheets, etc.) that require homogeneous material distribution and high throughput.

🛠️ Features & Benefits

• High Throughput and Homogeneous Mixing: Co-rotating twin screws create strong shear and distributive mixing, ensuring homogeneous melting and extrusion of materials. The long L/D 30 design increases residence time for complete plasticization, providing higher production capacity (up to several hundred kg per hour depending on the material).
• Modular Segmented Design: The barrel is divided into interchangeable segments (feeding, compression, metering zones) and equipped with replaceable inner liners. The screw shafts consist of bolted elements (transporting flights, kneading blocks, cutters). This modularity allows for quick repairs and formula/product changes without the need to replace the entire barrel.
• Extreme Durability: Made from precision heat-treated, hardened 38CrMoAlA alloy steel (sourced from Baosteel). Surfaces are treated with gas nitriding or bimetallic layers (hardening depth ~0.5–0.8 mm, hardness ~HRC56–60). These processes (nitriding, chrome plating, or tungsten carbide coating) provide exceptional wear and corrosion resistance with an outer hardness of up to HRC60–65.
• Stable Pressure and Quality: Precise tolerances between the screw and barrel (e.g., screw linearity ~0.015 mm, surface roughness ~Ra0.4) ensure consistent pressure and minimal material leakage. This results in stable extrusion and homogeneous product dimensions, enhancing final product quality and reducing waste.
• Material Flexibility: Its robust structure allows for processing a wide range of thermoplastics and compounds. Common materials include PVC, polyethylene (PE), polypropylene (PP), polystyrene (PS), ABS, and wood-plastic composites (WPC). The barrel processes filled and reinforced materials (high-calcium, WPC) without performance loss.
• OEM Compatibility: Specifically designed for extruders like KraussMaffei, Bausano MD series, JSW. The 125/30 model is fully compatible with the technical specifications of KraussMaffei's KMD 36D series or Bausano MD-125/30 extruders. Custom machining ensures perfect fit for your machine's assembly, barrel geometry, and heating requirements.

📊 Technical Specifications

🏢 Typical Applications

• PVC Pipe and Profile Extrusion: Production of rigid PVC pipes, cable ducts, and profiles. The barrel's long L/D ratio and high torque easily support high-calcium and filled PVC compounds.
• Sheet and Plate Production: Extrusion of flat sheets (SPC flooring, PVC wall panels, roofing sheets) using PP, PE, or PVC. Homogeneous melting prevents streaking and gel formation in the finished sheet.
• Wood-Plastic Composites (WPC): Extrusion of wood or calcium-filled PP/PE for decking, slats, and composite panels. Its robust design effectively manages abrasive structures within wood fibers or CaCO₃.
• ABS / Engineering Plastic Processing: Production of ABS profiles or durable plastic sheets. High shear mixing provides superior advantages in filled and recycled materials.
• General Compound Lines: Twin-screw compound production for PVC granules, HDPE grinding, or special blends where precise residence time and homogenization are required.

⚙️ Materials & Surface Treatment

• Main Material: High-strength 38CrMoAlA (JIS SACM645) alloy steel known for its high toughness and fatigue resistance.
• Heat Treatment: Vacuum or induction hardening and tempering up to approximately HB280-320 hardness, followed by gas nitriding for wear surfaces.
• Surface Coatings: Gas nitriding provides a hard layer (hardness ~HV920–1000, depth 0.5–0.8 mm). Alternatively, a bimetallic liner (2–3 mm thick alloy layer) can be applied (hardness HRC56–64). Tungsten carbide or hard chrome plating options are also available.
• Precision Machining: Screw grooves and channels are machined with tight tolerances to ensure efficient melting and minimal leakage (linearity ~0.015 mm, surface roughness Ra≤0.4 μm).
• Segment Surface Finishing: Barrel halves are machined in pairs, matched, and then heat-treated. Segments are sealed with O-rings or gaskets. End sections are prepared for quick-connect heating resistors or water cooling jackets as required by the extruder design.

🔄 Compatibility & OEM Fit

This 125/30 barrel is manufactured to match industry-leading twin-screw extruders. Specifically, it provides full compatibility with KraussMaffei 125-30 (KMD 36D series) and Bausano MD 125/30 PLUS machines with a 125 mm screw diameter and L/D ≈30 ratio. It can also be supplied for other brands with the same dimensions (JSW, Battenfeld, etc.).

Key OEM Parameters:

• Mounting and Orientation: Flange connection holes, feeding neck, and barrel body are manufactured according to the original technical specifications of the extruder.
• Heating / Cooling Zones: Configured according to your machine's control system (barrel resistances, water/air cooling circuits).
• Screw Configuration: Standard screw geometry or custom screw elements (transporting flights, kneaders, combinations of cutters) are provided according to the customer's process needs.
• Custom Developments: Special elements to prevent separation for high-filled materials or easily removable screw designs are available.

🔧 Installation & Maintenance Notes

• Preparation: Inspect barrel halves and screws before assembly. Clean all parts and check centering pins/guides.
• Assembly: Place barrel halves onto the body. Tighten segment bolts evenly according to torque values. Ensure gaskets or O-rings are seated properly.
• Alignment (Shaft Adjustment): Verify alignment of screw shafts and barrel (use linearity masters or comparators). Correct any axial misalignment to prevent wear.
• Connections: Connect thermocouples, cartridge heaters, and cooling pipes. Test heating zones individually. Ensure continuous flow in cooling lines during hydraulic testing.
• Run-In Procedure: Gradually heat the extruder while running empty (without raw material) at low speed; check for abnormal sounds or vibrations.
• Routine Maintenance: Implement standard lubrication and inspection program after initial run-in. Due to the modular design, replace only worn segments or screw elements instead of the entire screw. Keep detailed records of wear limits and grinding/maintenance intervals.
• Safety: Always turn off and lock out (LOTO) the main switch before opening the barrel and wait for it to cool down. Follow all OEM safety guidelines for high-temperature and high-pressure equipment.

🧪 Quality Control & Testing

• Material Certification: All steels come with material test reports (e.g., Baosteel certification for 38CrMoAlA).
• Dimensional Inspection: Screw diameter, pitch, linearity (target ±0.015 mm), and barrel inner hole integrity are verified using CMM (3D Measurement Machine) and special masters.
• Surface Checks: Hardness testing (Rockwell scale) confirms nitriding or alloy hardness (typically HRC56–60 for nitrided layer). Metallurgical sections are examined to verify layer depth and adhesion quality.
• Runout and Balance: Screw runout and dynamic balance tests prevent vibration under production load by ensuring stable rotation at high speeds.
• Leak Testing: Each barrel group is subjected to pressure testing with a sealing component to detect any leaks from screw channels to the outer barrel.
• Final Inspection: Visual and functional checks confirm the absence of sharp edges, correct labeling, and completeness of all documentation. A comprehensive compliance report covering all features is provided.