Material Drying
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POM product silver streaks
Fenómeno do problema
Silvery-white streaks appear on the product surface along the material flow direction, and the silver streaks are significantly reduced after drying the pellets and cleaning the barrel.
Análise das causas
The pellets contain water or humid air is drawn in during plasticizing and metering, and the water vapor forms bubbles in the melt that burst into silver streaks; gas produced by overheating decomposition of the resin also causes similar streaks.
Solução
①Fully dry the pellets at 80~90℃ for 3~4 hours; ②adjust back pressure to improve plasticizing venting; ③lower the temperature at overheated spots; ④remove stagnant material in the barrel and nozzle.
Conclusão principal
POM silver streaks need to be distinguished between two sources: moisture and decomposition; verify by drying first and then troubleshoot temperature, and item-by-item confirmation according to the mechanism can avoid blind machine adjustment.; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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