1. Screw Runs But No Output

Symptoms: Motor runs normally but no material exits the die.

Causes:

Discontinuous feed from the hopper

Foreign object jammed at the feed throat

“Bridging” — material clumping above the screw

Metal object lodged in the screw channel, blocking flow

Solutions:

Increase feed rate to maintain continuous, stable supply

Stop the machine and clear obstructions from the feed throat

Break up bridging by agitating material or using a bridge breaker

If metal contamination is confirmed, stop immediately, remove the screw, and extract the foreign object. Inspect blades for damage before restart.

2. Motor Will Not Start or Stops Instantly

Symptoms: Main motor fails to start or trips immediately after starting.

Causes:

Main power circuit disconnected or breaker tripped

Insufficient warm-up time — cold plastic creates excessive torque

Faulty heater or poor contact, leaving material partially solidified

Solutions:

Verify power supply, check circuit breakers, and confirm all safety interlocks are engaged

Allow full warm-up time per material specification (typically 30–60 minutes)

Check temperature displays against setpoints. Test heaters and thermocouples for failure or loose connections. Replace damaged components.

3. Material Leaking from Vent Port

Symptoms: Molten or partially melted plastic escapes from the degassing or vent opening.

Causes:

Contaminated feedstock with excessive moisture or volatile impurities

Feed rate too high for screw design, causing unstable extrusion pressure

Insufficient plasticization temperature — material not fully melted before reaching the vent zone

Solutions:

Pre-dry raw material or replace the filter mesh. Consider adding a pre-treatment drying stage for hygroscopic materials

Reduce feed rate to match screw capacity and stabilize extrusion

Gradually raise barrel temperature in the compression zone. Monitor melt temperature to avoid overheating and degradation

4. Motor Runs But Screw Does Not Rotate

Symptoms: Main motor turns but the screw remains stationary.

Causes:

Drive V-belt loose or worn, causing slip

Shear pin or safety key broken or dislodged

Solutions:

Adjust motor center distance to tighten the V-belt. Replace if cracked or glazed

Inspect the shear pin or safety key. If broken, identify the root cause — typically overload from foreign material or cold start — before installing a replacement