A PVC pipe fitting injection molding machine differs from a general-purpose machine. PVC material releases corrosive gas when heated. This gas damages the screw and barrel severely. If a manufacturer does not solve this problem, the machine’s service life shortens and product quality suffers. Buyers choosing a PVC pipe fitting injection molding machine manufacturer need to understand the core technology of the screw and barrel.
This article explains the screw and barrel technology for PVC injection molding machines. The first section explains why PVC needs a dedicated screw. The second section describes anti-corrosion and wear-resistant designs. The third section provides procurement evaluation criteria. The fourth section shows Haichen’s technical features.
Why PVC Needs a Dedicated Screw and Barrel?
PVC Material Properties and Equipment Requirements
PVC releases hydrogen chloride gas during melting. This gas corrodes ordinary steel. PVC has poor thermal stability and a narrow processing window. It decomposes when overheated. PVC melt has high viscosity, creating strong shear force on the screw.
Professional PVC injection molding machine manufacturers need to use special plasticizing screw designs. The barrel and nozzle must have strong corrosion resistance. All parts contacting PVC melt should not allow any adhesion or retention of the plasticizing melt.
Problems with General-Purpose Screws in PVC Production
| Problem | Consequence |
|---|---|
| Screw corrosion | Pitting on surface, uneven plasticizing |
| Barrel wear | Increased clearance, melt backflow |
| Material retention | Black spots, yellowing |
| Nozzle blockage | Injection pressure fluctuation |
Haichen’s Solution
Haichen designs dedicated screws for PVC characteristics. We use bimetallic screws and barrels with hardness above HRC65. This configuration resists corrosive gas erosion and extends equipment service life.
Specific Anti-Corrosion and Wear-Resistant Technologies
Key Screw and Barrel Technologies
PVC-specific injection molding machines need optimization in three areas: material, process, and structure. Each technology affects production stability and product quality.
Bimetallic Screw Technology
A bimetallic screw has an alloy layer fused onto the base material. The alloy layer hardness reaches HRC56-65 with thickness of 0.8-3.0mm. This alloy layer resists corrosion from PVC decomposition. When the surface wears, it can be repaired, reducing replacement costs.
Screw Geometry Parameters
PVC screws typically have an L/D ratio of 18:1 to 22:1 and a compression ratio of 2:1 to 2.5:1. The compression zone length increases to improve plasticizing efficiency. The screw tip uses a pointed design to prevent material buildup.
PVC pipe fitting molds usually have many core-pulling actions. Under the same clamping force or shot volume, pipe fitting molds need more space for core pulling. Therefore, professional PVC pipe fitting injection molding machine manufacturers need to reserve enough clearance in the door design and use larger hydraulic motors to meet the high requirements of PVC plasticizing.
Barrel Anti-Corrosion Design
The barrel inner wall undergoes nitriding treatment. The nitriding layer depth is 0.45-0.8mm with surface hardness HV900-1000. Barrel temperature control uses multi-zone PID regulation. Each zone controls independently to prevent local overheating.
Haichen’s Process Standards
Haichen PVC-specific machines use bimetallic screws and barrels. All parts contacting PVC receive anti-corrosion treatment. Screw geometry parameters are optimized for PVC to reduce material shear heat. These designs have earned Haichen CE safety certification.
Procurement Evaluation Criteria
How to Evaluate PVC Injection Molding Machine Suppliers?
Buyers choosing a pvc plastic injection molding machine supplier should focus on screw and barrel technical details. The following five criteria help buyers make informed decisions.
Evaluation Criteria Table
| Evaluation Item | Check Points | Acceptance Standard |
|---|---|---|
| Screw material | Bimetallic or chrome-plated | Hardness HRC55+ |
| Barrel inner wall | Nitrided | Hardness HV900+ |
| Screw parameters | L/D ratio, compression ratio | 18:1-22:1 / 2:1-2.5:1 |
| Nozzle design | PVC-specific | Anti-retention structure |
| Temperature control | Zone control accuracy | ±1°C |
Haichen PVC Machine Technical Features
Haichen’s Screw and Barrel Solutions
Haichen has over ten years of injection molding machine production experience. Our PVC-specific machines have been verified in actual production. The table below shows Haichen’s technical configurations for screws and barrels.
Haichen Technical Configuration
| Technical Item | Haichen Configuration |
|---|---|
| Screw material | Bimetallic, hardness HRC56-62 |
| Barrel inner wall | Chrome-plated + nitrided |
| Screw L/D ratio | 20:1 (optimized for PVC) |
| Nozzle | PVC-specific anti-retention design |
| Safety gate | Widened for core-pulling molds |
| Hydraulic motor | Increased torque for high-viscosity PVC |
Haichen is a professional PVC pipe injection molding machine manufacturer offering PVC-specific models with clamping force from 1700kN to 4000kN. Buyers needing detailed technical specifications can contact the Haichen sales team for documentation.
