Injection Molding
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PMMA Stress Cracking
Problembeschreibung
Products crack during assembly, solvent contact or after storage, often starting from sharp corners and screw bosses.
Ursachenanalyse
PMMA is brittle and sensitive to residual stress; high stress from fast injection, cold demolding, sharp corners and press fits cracks under solvent or load.
Lösung
①Slow injection; ②Sufficient cooling and gentle demolding; ③Change sharp corners to rounds (25%~60% of wall thickness); ④Anneal at 70~80℃ for 2~4 hours; ⑤Avoid contact with incompatible solvents.
Wichtigste Erkenntnis
PMMA delayed cracking = the delayed detonation of internal stress, annealing is the insurance.
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