Material Drying
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PARA Shrinkage Depression
Problem Phenomenon
PARA products show shrinkage depression and insufficient density; multiple factors of excessive wall thickness, gas and thermal shrinkage.
Cause Analysis
Insufficient product density; gas contained in the melt; product wall thickness too thick exceeding 7~10mm; large thermal shrinkage; insufficient drying with moisture influence.; during on-site troubleshooting, verify item by item according to this mechanism, avoiding blind machine adjustment based only on experience
Solution
①Increase melt volume, raise injection pressure and extend injection time; ②Fully dry the material; ③Product thickness not exceeding 7~10mm; ④Reduce barrel temperature and mold temperature.
Key Takeaway
The 7~10mm wall thickness upper limit for PARA shrinkage depression is a design red line; drying and density management are given equal weight; lowering temperature reduces thermal shrinkage.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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