Molds & Tooling
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COC Gate Mark and Jetting Mark
Problem Phenomenon
Jetting snake patterns and gate halo marks appear near the gate of COC products, especially obvious on transparent parts, and the effect fluctuates after adjusting the temperature.
Cause Analysis
The melt passing through the small gate at high speed produces jetting, and the melt strand condenses before touching the wall, forming snake patterns; excessive shear in the gate area produces shear heat and orientation streaks; low mold temperature aggravates condensation marks.
Solution
①Adopt multi-stage injection, passing the gate area at low speed and then speeding up; ②enlarge the gate or switch to fan or overlap gates; ③increase mold temperature to enhance replication and fusion; ④keep the gate away from the main optical viewing area.
Key Takeaway
COC gate mark treatment mainly relies on multi-stage injection and gate design; the gate position of transparent parts should avoid the main viewing area at the design stage; shear control runs through the whole process.
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