Pvc screw barrel

For PVC processing, the material must withstand high friction and corrosive hydrochloric acid release. You should prioritize 38CrMoAlA (JIS SACM645) nitrided steel for standard applications. For high-filler PVC or recycled materials, Bimetallic alloys (such as Tungsten Carbide or Nickel-based alloys) are essential to provide a hardness of HRC 58-64, significantly extending the service life compared to standard nitriding.

PVC is heat-sensitive; therefore, the screw must have a low compression ratio and a specialized flight geometry to prevent material degradation. For UPVC (Rigid), a conical twin screw is often preferred for better pressure buildup, while for SPVC (Soft), a parallel twin screw or single screw with a cooling system is ideal. Ensure the design includes internal oil cooling holes for precise temperature control.

The inner wall of the barrel should have a surface roughness of Ra 0.4μm or less to prevent material stagnation. The straightness tolerance should be within 0.015mm per meter. For enhanced corrosion resistance against PVC additives, request Chrome plating or HVOF (High-Velocity Oxy-Fuel) thermal spraying to create a protective barrier against chemical erosion.

Ensure the manufacturer follows ISO 9001:2015 for quality management. Since these are pressure-bearing components, check for CE certification if importing to Europe. It is critical to request a Material Analysis Report and a Nitriding Layer Depth Report (typically 0.5mm - 0.8mm) to verify that the hardening process meets industrial durability requirements.

Screw barrels are precision-engineered parts. Never order based on model names alone. You must provide detailed technical drawings (CAD or PDF) including length, diameter, and connection flange dimensions. If drawings are unavailable, send a physical sample to the supplier for mapping. Always use Made-in-China.com's Inspection Service to verify dimensions before the final balance payment is made.

Focus the negotiation on 'Life Cycle Value' rather than just the unit price. Ask for a guaranteed service life (e.g., 10,000+ hours). Negotiate for tiered pricing if you plan to replace barrels for multiple production lines. Request that the supplier includes wear-measurement tools or spare heater bands as part of a bulk package to increase the deal's total value.

Screw barrels are heavy and prone to bending or rusting during sea freight. Insist on vacuum-sealed anti-rust oil coating and wrapping in VCI (Volatile Corrosion Inhibitor) film. The outer packaging must be a fumigated reinforced wooden crate with internal supports to prevent the screw from shifting, which could cause permanent warping during transit.

Utilize Secured Trading Services on Made-in-China.com to ensure funds are only released upon proof of shipment. For high-value bimetallic orders, require a Third-Party Hardness Test (Rockwell) and a Spectrometer Analysis of the alloy composition. Ensure the contract specifies a 12-month warranty period against premature wear or cracking under normal operating conditions.