Molds & Tooling
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PET preform melt fracture
Problem Phenomenon
Sharkskin-like rough texture appears on the preform surface, the transparency decreases, and the texture diminishes after increasing the melt temperature.
Cause Analysis
When the melt passes through the gate, the shear rate is too high, and the surface melt fractures to form periodic roughness; low melt temperature and a small gate both aggravate this phenomenon.; 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 the melt temperature; ②enlarge the gate size to reduce shear; ③optimize the injection speed curve; ④check the hot runner gate wear.; after adjustment, take consecutive samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PET preform melt fracture is mostly seen in high-speed filling; coordinated adjustment of the three parameters of temperature, gate, and speed can eliminate the texture while ensuring the cycle.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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