Processing Machinery
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POM excessive back pressure degradation and discoloration
Fenómeno do problema
The product color yellows and performance becomes brittle; process records show the back pressure setting is too high, and the color recovers after lowering the back pressure.
Análise das causas
High back pressure increases screw shear heat, causing the actual material temperature to exceed the set value and triggering degradation and discoloration; excessive back pressure also extends plasticizing time, aggravating thermal history.; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solução
①Control back pressure in the low range of 3~8MPa; ②monitor actual melt temperature; ③increase melt temperature to compensate plasticizing if necessary; ④avoid long-time high back pressure operation.; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Conclusão principal
POM is shear sensitive, and back pressure is an overlooked source of temperature rise; low back pressure with reasonable melt temperature is a safe setting that balances plasticizing quality and degradation prevention.; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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