Injection Molding
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Low Weld Line Strength of PEEK
Problem Phenomenon
The strength at weld lines of PEEK products decreases significantly, cracking along weld lines under stress, especially prominent in deep-cavity multi-gate parts and behind holes, with visible meeting line marks in appearance.
Cause Analysis
When the two melt fronts meet, their temperature has already dropped, and PEEK's high viscosity makes molecular chain segment diffusion and entanglement insufficient; low mold temperature, insufficient injection speed, and poor venting further weaken the interface bonding.
Solution
①Raise the mold temperature and melt temperature, and speed up injection so the fronts meet while remaining at high temperature; ②Improve venting and set overflow wells in the meeting area; ③Optimize the gate position to move the weld line to a low-stress area.
Key Takeaway
PEEK weld lines cannot be completely eliminated — they can only be relocated and strengthened; high-temperature meeting is the first guarantee of interface strength; overflow wells are a worthwhile scrap cost for load-bearing parts.
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