Injection Molding
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PCL High Melt Viscosity and Difficult Filling
Problem Phenomenon
PCL '2079851475616104452 filling is incomplete, with short shots at thin walls and long flow paths, still difficult even with high pressure and high speed.
Cause Analysis
PCL melt phase has high viscosity and poor flow; higher temperature is needed to reduce viscosity but there is degradation risk; high molecular weight aggravates it; runner and gate resistance.; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
①Appropriately increase melt temperature to 140~180°C; ②optimize injection pressure and speed; ③enlarge runner and gate sizes; ④select molecular weight grades; ⑤increase mold temperature.
Key Takeaway
PCL high viscosity is the main processing challenge; temperature and structure are equally important; molecular weight selection affects processability.; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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