Molds & Tooling
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PA6 Shrinkage and Post-Shrinkage
Problembeschreibung
The part dimensions are qualified at demolding, but after several days of storage the dimensions go out of tolerance and assembly fit fails
Ursachenanalyse
PA6 shrinkage is 1-1.5% and post-shrinkage continues after molding, while water absorption expansion partially offsets the shrinkage; the dual action of shrinkage and expansion causes dimensions to drift with time and ambient humidity
Lösung
①Allow margin in the mold according to the 1-1.5% shrinkage and reserve space for mold trial and correction; ②Perform conditioning treatment on precision parts after molding to pre-stabilize dimensions; ③Perform dimensional inspection after conditioning reaches equilibrium
Wichtigste Erkenntnis
PA6 dimension management must account for both the shrinkage bill and the water absorption bill; conditioning pretreatment plus post-equilibrium inspection is the only way to lock dimensions in the service state; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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