Injection Molding
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PVC Injection Weak Weld Line
Problem Phenomenon
Cracking at weld line, insufficient strength.
Cause Analysis
PVC melt has high elasticity, flow front convergence temperature insufficient; degraded flow front even weaker; poor venting entrapping gas further weakens it; during on-site troubleshooting, verify item by item according to this mechanism, avoid blindly adjusting the machine based solely on experience.
Solution
①Raise temperature and speed; ②Vent at convergence; ③Adjust gate position/number, change flow direction and convergence position; ④Prevent degradation; ⑤Set overflow wells at convergence to lead cold flow front out of the cavity.
Key Takeaway
PVC weld line = 'temperature + venting + anti-degradation': PVC melt has high elasticity and converges with difficulty, temperature and venting must be given sufficiently, and more importantly prevent degraded flow front from making the weld line brittle.
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