Step 1: Verify External Conditions and Overall Process
This is the starting point of troubleshooting. First, ensure that the external environment and basic parameters for the production line are correct.
Check utility systems: Verify that the workshop's power, water, and compressed air supplies are stable, and that all pressure readings are within normal ranges.
Verify raw material condition: Confirm that the raw materials are correct and free from moisture (especially important for materials like PE), and check that the formulation and mixing ratios meet process requirements.
Verify operating parameters: Quickly review all key process parameters on the control panel to ensure their set values have not been accidentally altered.
Step 2: Inspect Section by Section to Pinpoint the Problem Area
If external conditions are normal, the problem lies within the production line, and you need to trace the issue back by examining product defects. The production line primarily consists of the following four systems, with different defects typically corresponding to different areas.
1. Extruder Section
Risk Factors: Instability, fluctuations ("shark skin" phenomenon), poor plasticization, or scorching.
Related Issues: Fluctuations in output, rough pipe surface with an orange peel texture, carbonization on the inner wall with black spots.
2. Die Section
Risk Factors: Uneven wall thickness, surface grooves, bending, rough surface, rough inner wall.
Related Issues: Uneven pipe wall thickness, wavy grooves or patterns on the outer surface, bending.
3. Sizing and Cooling Section
Risk Factors: Excessively high or uneven water temperature, insufficient or unstable vacuum, scratches on the sizing sleeve, and clogged spray nozzles.
Related Defects: Pipe dimensional deviations, roundness deviations, rough outer surface, longitudinal scratches on the surface.
4. Traction and Cutting Section
Risk Factors: Slippage, unstable speed, encoder misalignment, blade wear, limit switch failure.
Related Defects: Abnormal pipe outer diameter, wall thickness fluctuations, inaccurate cutting length, uneven cut edges.
Step 3: Conduct a detailed troubleshooting analysis based on the symptoms of the problem
1. Longitudinal grooves on the outer surface
→ This is usually caused by scratches or material buildup on the inner wall of the sizing sleeve or die.
Quick check: After stopping the machine, feel the inner wall of the sizing sleeve with your hand to see if it is smooth. If there are any rough spots, gently sand them down with fine sandpaper.
2. Wavy rings (resembling waves) on the pipe wall
→ This is caused by unstable cooling water, fluctuating vacuum pressure, or slippage in the haul-off.
Quick check: Ensure the water spray in the cooling tank is flowing continuously; check if the vacuum gauge reading is stable; verify that the haul-off belt is firmly pressing against the pipe.
3. Uneven wall thickness
→ Common causes: Die misalignment, excessive temperature difference in the heating zones, or fluctuating haul-off speed.
Quick check: Check the temperature readings around the die; a difference exceeding 5°C is abnormal; observe whether the traction wheels are slipping; realign the die head and sizing sleeve.
4. No vacuum or very low vacuum
→ The vacuum pump is faulty, there is an air leak in the piping, or the small holes in the mandrel are blocked.
Quick Check: Listen for unusual noises from the vacuum pump; check if the inlet hose is properly connected; use a thin wire to clear the small hole in the center of the core mold.
5. Pipe is bent (not straight)
→ The production line is not aligned in a straight line.
Quick Check: Visually inspect or use a string to check whether the main machine, setting table, haul-off machine, and cutting machine are aligned in a straight line.