100 Common Troubleshooting Tips For Twin-Screw Extrusion Lines (Part 1)

This practical guide collects typical faults and corresponding solutions occurring during twin-screw extrusion production. It covers the main unit, feeding system, die and head assembly, helping on-site staff quickly locate problems, cut downtime and maintain steady production.

1. Main Unit & Feeding System

1. Hopper bridging / No feeding: Materials form an arch above the feed opening.
Solution: Fit vibrators or mechanical agitators on the hopper to break up material arches.

2. High torque on main motor: Caused by foreign objects inside screws or insufficient preheating.
Solution: Check and replace blocked screen packs, and raise barrel temperature properly.

3. Unstable feed rate: Feed screw blockage or material bridging in the hopper.
Solution: Clean the feed channel and remove built-up materials.

4. Overflow at vacuum vent: Vacuum pressure is too high or materials are not fully melted.
Solution: Lower vacuum level and increase temperature of melting zones.

5. Abnormal noise from screws: Friction between screws and barrel.
Solution: Inspect for bent screws or installation misalignment.

6. Inaccurate temperature reading: Loose thermocouple wiring or electromagnetic interference.

7. Temperature out of control: Damaged solid-state relay.
Solution: Replace the faulty component.

8. Oil leakage on barrel body: Aging or worn sealing rings.

9. Gearbox overheating: Insufficient oil volume or damaged bearings.

10. VFD alarm triggered: Unstable power voltage or motor overload.

11. Screw slipping: Overheating in the feed zone leads to early material melting.

12. Sudden output drop: Blocked screen packs or severe screw wear.

13. Failed restart after shutdown: Residual materials inside barrel have solidified.
Solution: Fully purge the barrel before stopping production.

14. Weak vacuum suction: Low water level or poor sealing of vacuum system.

15. Damaged barrel heaters: Loose wire connections.

16. Feeder motor burnout: Long-term low-speed operation without effective cooling.

17. Shaft end leakage: Worn shaft seals.

18. Excessive unit vibration: Loose foundation bolts or unbalanced drive shafts.

19. Blocked cooling jacket: Limescale accumulation.
Solution: Carry out professional descaling regularly.

20. Strange odor in control cabinet: Overheated circuit wires due to overload.
Solution: Inspect wiring immediately to avoid safety risks.

2. Die & Head Section

21. Uneven material output: Improper adjustment of die gap.

22. Visible weld lines on products: Unreasonable flow channel design or insufficient back pressure.

23. Fluctuating die pressure: Unstable operation of melt pump.

24. Smoke coming out of die: Local overheating causes material degradation.

25. Carbon deposits inside die: Materials stay too long in dead zones.

26. Surface scratches on finished goods: Hard impurities or scratches on die lip.

27. Die drooling: Excess temperature reduces melt strength.

28. Leakage at die joints: Loose bolts or damaged gaskets.

29. Uneven wall thickness: Misaligned die core.

30. Slow heating of die assembly: Partial cartridge heaters stop working.

31. Buildup on die lip: Additive precipitation.
Solution: Clean die lip or adjust raw material formula.

32. Deviated inner diameter size: Wrong sizing sleeve or miscalculated shrinkage rate.

33. Excess die pressure: Overly dense screen packs or narrow die opening.

34. Pulsating output: Screw structure does not match processing materials.

35. Die cannot be opened: Materials solidified while the die was still hot.

36. Offset flow distributor: Installation deviation.

37. Rough inner die surface: Worn chrome coating.

38. Broken heating wire of die core: Cable squeezed and broken.

39. Deformed breaker plate: Instant pressure surge.

40. Malfunction of die temperature control unit: Blocked oil pipelines.
To be continued