Common PVC Twin Screw Extruder Problems and Solutions: A Practical Troubleshooting Guide

PVC twin screw extruders are widely used for manufacturing PVC drainage pipes, water supply pipes, electrical conduits, window profiles, and other plastic products. During long-term production, operators may encounter problems such as abnormal motor current, unstable extrusion, material burning, screw wear, or black streaks on the pipe surface.

If these issues are not identified and resolved promptly, they can reduce product quality, increase maintenance costs, and even damage key machine components such as the gearbox, screw, and barrel.

This guide summarizes several common problems encountered during PVC extrusion production and provides practical troubleshooting methods based on real production experience.

1. What Is the Normal Current of a 65 Conical Twin Screw Extruder?

For a SJZ65 conical twin screw extruder producing standard PVC drainage pipes, the motor current normally operates between 40 A and 50 A.

Under normal production conditions, the operating current should not exceed 60 A.

Running the machine above this level for extended periods increases screw torque, accelerates gearbox wear, and may even cause screw damage. Therefore, monitoring motor current is one of the simplest ways to evaluate whether the extrusion process is operating correctly.

2. Why Does the Extruder Current Suddenly Increase?

A sudden increase in motor current usually indicates that the screw is experiencing excessive resistance.

Several factors may cause this problem.

Gearbox Bearing Damage

Damaged gearbox bearings increase mechanical resistance, causing the motor load to rise rapidly.

Poor Material Flow

If the PVC compound loses its normal flowability because of formulation changes, insufficient lubrication, or overheating, screw torque will increase immediately.

3. Why Does the Current Fluctuate When Producing High-Calcium PVC Pipes?

Many PVC pipe manufacturers increase calcium carbonate content to reduce raw material costs.

However, high-calcium formulations require much better feeding stability.

If the machine operates normally during startup but the current begins fluctuating after four or five hours, possible causes include:

• unstable feeding;

• inconsistent material mixing;

• mismatch between screw speed and feeding speed;

• insufficient lubrication in the PVC formulation.

Instead of adjusting only machine parameters, manufacturers should also optimize the formulation and ensure continuous, uniform material feeding.