Molds & Tooling
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Corrugation/roughness on the inner wall of PP-R pipes
Problem Phenomenon
The inner wall of PP-R pipes shows corrugated undulations or roughness, affecting water flow resistance and hygienic performance, while the outer wall may be normal.
Cause Analysis
Uneven distribution of the melt or pressure fluctuation by the die head (die and mandrel) makes the melt flow unstable before sizing; improper sizing cooling, unsuitable mandrel temperature, or local melt degradation and adhesion all cause poor inner wall forming.
Solution
①Check the die head flow channel and spider design to ensure uniform melt distribution; ②stabilize the extrusion pressure and temperature; ③optimize the sizing sleeve and cooling to avoid premature or delayed sizing of the inner wall; ④regularly clean the die head deposits; ⑤select a low-shear die head with a wide forming window.
Key Takeaway
PP-R inner wall problems mostly originate from die head distribution and pressure stability, not simply temperature; inner wall forming quality reflects the 'state' of the melt before entering sizing, so investigate from both the die head and pressure fluctuations.
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