Processing Machinery
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Weld line cracking of PP thin-wall parts
Fenómeno del problema
Stress concentrates at the weld line of thin-wall parts, and they crack along the weld line after being subjected to external force.
Análisis de la causa
The molecular chains are not fully fused where multiple melt fronts converge; thin-wall parts have fast filling speed and more obvious front cooling, so the weld line strength problem is amplified.; during on-site investigation, verify item by item according to this mechanism to avoid blindly adjusting the machine based only on experience
Solución
①Reduce the number of gates or change the gate position to relocate the weld line; ②increase the melt and mold temperatures; ③increase the injection speed in the convergence area; ④set vents and overflow wells at the confluence.
Conclusión clave
Thin-wall part weld lines should be kept away from stress-bearing areas by design means; process temperature and speed increases can only partially improve strength.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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