Material Drying
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Silver streaks on PP injection molded parts
Fenómeno del problema
Silvery-white streaks appear on the product surface along the flow direction, which diminish after drying.
Análisis de la causa
Moisture adsorbed on the surface of PP pellets vaporizes in the melt; degradation gas or shear overheating can also produce similar silver streaks.; during on-site investigation, verify item by item according to this mechanism to avoid blindly adjusting the machine based only on experience
Solución
①Dry the pellets appropriately; ②control the melt temperature to prevent degradation; ③reduce the screw speed to reduce shear; ④check the moisture content and quality of the regrind.; after adjustment, continuously sample and verify the effect, and resume mass production after confirming stability
Conclusión clave
Investigate PP silver streaks along the three clues of moisture, degradation, and shear; verify by drying first, then check the temperature history.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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