Injection Molding
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PPO gate jetting snake patterns
Problem Phenomenon
Jetting flow marks (snake patterns) appear in front of the gate of PPO products, appearance defects are concentrated in the gate area, especially obvious on large products.
Cause Analysis
The high-viscosity PPO melt jets when passing through a small gate, and the melt strand condenses before contacting the wall, forming snake patterns; mismatched gate form and size is the main cause; excessive injection speed aggravates jetting.
Solution
①Select film-shaped or fan gates for large parts; ②pin-point or submarine gates can be used for small parts but with the diameter appropriately enlarged; ③use slow-fast multi-stage injection in the gate area; ④design runner dimensions with large diameters.
Key Takeaway
PPO jetting marks are an exclusive defect explicitly pointed out by material suppliers; gate form selection is more curative than parameter adjustment; multi-stage injection is an effective process compensation means.
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