Pipe Extrusion Troubleshooting

Problems

Possible Causes

Suggested Solutions

Unbalanced wall thickness
  1. Improper die setting
  2. Improper alignment of die & take-off units
  3. Hot & cold spots in die
  1. Adjust the die setting
  2. Check for alignment
  3. Check for uniformity in die heating

Surface defects appearing at the die
  1. Maybe due to moisture in material
  2. Improper mixing of resin & additives
  3. Foreign contamination
  4. Due to over heating
  1. Pre-dry material
  2. Increase rpm back pressure for better mixing
  3. Check for foreign material
  4. Check for the functioning of temperature controller.

Rough surface inisde or outside
  1. Low melt temperature
  2. Material sticking on the mandrel or sizing sleeves can cause roughness
  3. Very high linear extrusion speeds can cause melt fracture at the die
  4. Locate the exact point at its origin
  5. May be caused by misalignment of sleeve
  1. Increase melt temperature
  2. Check for material sticking on mandrel or sizing sleeves
  3. Increase melt temperature longer die hands
  4. If a strip of roughness on underside, then it is caused by uneven water cascading. Direct another cascade from bottom to upward.
  5. Check for alignment
Spitty pipe
  1. May be due to failure along weld lines
  2. Extrusion may be too cold or too fast
    3.
  1. Raise melt temperature
  2. Improve die design by increasing land length to develop more pressure.
    3.

Pipe out of round
  1. Sizing devices in adequate or out of shape
  2. Pipe is too warm when it reaches the puller
  1. Check for sizing devices
  2. Adequate cooling of pipe before reaching puller.