Plastic Pipe Extrusion Production Line Faults and Maintenance

The plastic pipe extrusion production line, as the core equipment for plastic pipe manufacturing, has its operational stability directly related to product quality, production efficiency, and enterprise costs. However, during long-term continuous operation, due to fluctuations in raw materials, equipment aging, improper operation, or environmental factors, the production line inevitably experiences various faults. Scientifically identifying common problems and implementing standardized maintenance strategies are crucial to ensuring efficient, safe, and high-quality production.

I. Common Faults and Troubleshooting of the Extrusion Main Machine

1. Unstable or fluctuating extrusion volume
Possible causes:
Screw wear or material accumulation;
Damaged heating elements leading to uneven temperature;
High moisture content or impurities in the raw materials;
Drive motor or inverter malfunction.
Suggested solutions:
Regularly clean the screw and barrel, and check for wear (every 500–1000 hours);
Use an infrared thermometer to calibrate the temperature in each zone;
Ensure raw materials are dry (especially for hygroscopic materials such as PVC and PET);
Check electrical system wiring and parameter settings.
2. Melt temperature too high or yellowing (especially PP, PVC)
Causes: Shear overheating, unreasonable screw design, excessive back pressure, insufficient stabilizer.
Solutions:
Optimize screw speed and feeding ratio;
Use a low-shear barrier screw;
Check if the vent is blocked (for twin-screw extruders);
Appropriately increase heat stabilizers or lubricants in the formula.

II. Forming and Sizing System Faults

1. Uneven pipe outer diameter or excessive ovality
Main causes:
Insufficient or uneven vacuum in the vacuum sizing tank;
Cooling water temperature too high or uneven spraying;
Mold concentricity deviation;
Mismatch between traction speed and extrusion speed.
Solutions:
Clean the vacuum holes and check the performance of the vacuum pump;
Control the cooling water temperature at 15–25℃ (depending on the material);
Regularly calibrate the mold installation accuracy;
Enable speed linkage control (extrusion-traction synchronization).
2. Pipe surface is rough, scratched, or exhibits a “shark skin” phenomenon.
Analysis:
Carbon buildup or damage to the die lip;
Melt fracture, commonly seen in high-speed extrusion;
Rapid cooling leading to surface stress concentration.
Countermeasures:
Clean or polish the die opening;
Reduce extrusion speed or increase processing temperature;
Add processing aids (such as fluoroelastomers) to improve melt flowability.

III. Traction and Cutting System Problems

1. Traction slippage or insufficient clamping force
Commonly seen in: small-diameter thin-walled pipes or pipes with smooth surfaces (such as PEX).
Solutions:
Replace the track pads with those having a higher coefficient of friction;
Adjust the pneumatic or hydraulic clamping force;
Add anti-slip guide rollers before the traction section.
2. Inaccurate cutting length or uneven cut
Reasons:
Encoder signal interference or measuring wheel slippage;
Cutting blade dullness or looseness;
The pipe is cut before it is fully cooled.
Maintenance points:
Regularly calibrate the encoder and measuring wheel;
Check and tighten the blade sharpness every shift;
Ensure the cutting point is in a fully cooled area.

IV. Electrical and Control System Faults

PLC crash or communication interruption: Check power supply stability and proper grounding, avoid strong electrical interference;
Temperature control failure: Replace thermocouples or solid-state relays, regularly calibrate the temperature control module;
Human-machine interface (HMI) unresponsive: Restart the system, back up the program, prevent viruses or memory card damage.
Tip: It is recommended to configure UPS power for critical control units and establish a complete equipment parameter backup mechanism.

The stable operation of a plastic pipe extrusion production line depends not only on high-quality equipment hardware but also on a scientific maintenance system and standardized operation management. Through the concept of “prevention first, repair second,” combined with intelligent monitoring methods (such as vibration sensors and AI early warning systems), companies can significantly reduce failure rates, extend equipment life, and improve product consistency. In the context of the current manufacturing industry’s transformation towards lean and digital manufacturing, shifting equipment maintenance from “passive emergency repair” to “proactive health management” has become an important path for pipe manufacturers to enhance their core competitiveness.