Common Problems And Solutions In The Process Of PE Pipe Extrusion

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In the plastic pipe production line, the operator’s unskilled technology and the machine operation will cause the plastic pipe to appear rough on the outer surface, jitter ring inside, uneven wall thickness, insufficient roundness and so on. Therefore, timely adjustment of plastic pipes’ production process and troubleshooting of the plastic pipe production line can improve product quality.

1. The outer surface of the plastic pipe is rough

  • Adjust the process temperature;
  • Lower the cooling water temperature, the best cooling water temperature for PE pipes is 20~25℃;
  • Check the waterway to see if there is blockage or insufficient water pressure;
  • Check whether the heating ring of the barrel, head, etc. is damaged;
  • Adjust the inlet water flow of the sizing sleeve;
  • Check the properties and batch numbers of raw materials;
  • Check the temperature of the core of the mould. If it is higher than the temperature of the die section, lower the temperature of the heart;
  • Clean the aggregates of the mould;
PVC PPR PE pipe extrusion line
PVC PPR PE pipe extrusion line

2. Grooves appear on the outer surface of the plastic pipe

  • Adjust the water outlet pressure of the sizing sleeve, and the water output is required to be balanced;
  • Adjust the nozzle angle in the vacuum shaping box to make the pipe cool evenly;
  • Check the die, sizing a sleeve, cutting machine, and other hardware for debris, burrs, etc.;

3. Grooves appear on the inner surface

  • Check whether water enters the inner tube. If water enters, pinch the tube embryo of the mould just after the exit to seal the inner cavity;
  • Reduce the internal temperature of the mould;
  • Clean and polish the mould;
PVC PPR PE pipe extrusion line
PVC PPR PE pipe extrusion line

4. A jitter ring appears inside the pipe

  • Adjust the water outlet of the sizing sleeve to make it evenly;
  • Adjust the vacuum degree of the second chamber so that the vacuum degree of the back chamber is slightly higher than the vacuum degree of the front room;
  • Check whether the vacuum seal is too tight;
  • Check whether the tractor is shaking;
  • Check whether the main machine discharges evenly;

5. No vacuum

  • Check if the water inlet of the vacuum pump is blocked. If it is blocked, unblock it;
  • Check whether the vacuum pump is usually working;
  • Check whether the vacuum pipeline is leaking;
  • Check whether the small hole in the middle of the core mould compression screw is blocked. If it is blocked, use a thin iron wire to clear it;

6. The outer diameter of the pipe is out of tolerance

  • The size of the outer circle can change by adjusting the vacuum degree;
  • The size of the outer ring can change by altering the traction speed;
  • Correct the size of the inner hole of the sizing sleeve;

7. The roundness of the pipe is out of tolerance

  • Adjust the nozzle angle in the vacuum setting machine and spray box to cool the pipe uniformly;
  • Check the vacuum forming apparatus, the water level in the spray box, and the pressure of the water pressure gauge to make the spray volume large and powerful;
  • Check the water temperature of the vacuum setting machine and spray box. If it is >35℃, a chilled water system or a spray cooling box should add;
  • Check the waterway and clean the filter;
  • Adjust the process;
  • Check and correct the roundness of the inner hole of the sizing sleeve;
  • Adjust the pipe guide and clamping device to update the ovality of the pipe;
PVC PPR PE pipe extrusion line
PVC PPR PE pipe extrusion line

8. Uneven pipe wall thickness

  • Adjust the wall thickness on the mould;
  • Adjust the nozzle angle in the vacuum setting machine and spray box to make the pipe cool evenly; adjust the water output of the sizing sleeve to make it even;
  • Disassemble the mould, check whether the screws inside the mould are loose, and re-tighten it;

9. The plasticizing temperature is too high

  • Adjust the process;
  • Adjust the heating temperature of the mould core and ventilate and cool the mould;
  • The sheer heat of the screw is too high, replace the screw;

10. Inaccurate cutting length

  • Check whether the long wheel pressed tightly;
  • Check whether the long wheel swings, and tighten the fixing bolts of the long wheel frame;
  • Check whether the stroke switch of the cutting machine is damaged;
  • Check whether the rotary encoder is damaged;
  • Whether the wiring of the rotary encoder is disconnected (whether the aviation plug seat is in good contact);

Each stand-alone enclosure (PE terminal) should be grounded separately to a total grounding point for reliable grounding. The grounding point should have a grounding stake that meets the electrical grounding requirements. It is not allowed to connect the stand-alone enclosures (PE terminals) in series and ground. Otherwise, they will introduce Interference pulse, causing inaccurate cutting length;

11. Co-extrusion label problem

Diffusion of co-extrusion identification strips: Generally, it causes improper selection of users’ co-extrusion materials. Unique materials, such as PE, should be used. If necessary, the temperature of the extrusion section can reduce;

The co-extruder cannot squeeze out: stop the main extruder, turn on the co-extrusion machine first, and turn on the co-extrusion device for about 10 minutes before turning on the host;

Co-extrusion marking strip is too thin or too wide: Generally, it causes by the mismatch between the extrusion volume of the co-extrusion machine and the traction speed of the pipe and should be adjusted, the frequency of the frequency converter of the co-extrusion engine or change the traction speed to match the two rates;

The second is the reason why the cooling water jacket of the unloading section of the co-extruder is not passing through the cooling water;

In the actual production process of the pipe production line, there will be other abnormal situations, which should deal with according to the exact condition.

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