Material Drying
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Bubbles in thick-walled PVA '2079851475616104452
Problembeschreibung
Dense bubbles of 0.1-0.5mm appear inside PVA injection molded thick-walled products, concentrated in the wall thickness center
Ursachenanalyse
Holding pressure insufficient <40MPa or holding time short, thick-wall center not compacted; raw material contains moisture; injection speed too fast, entrapping air; poor mold venting
Lösung
1) Increase holding pressure to 60-80MPa; 2) Extend holding time so the thick wall is fully compacted; 3) Fully dry raw material to moisture <0.02%; 4) Add vent grooves or vent pins to the mold; 5) Gradually decelerate injection to avoid air entrapment
Wichtigste Erkenntnis
Thick-wall bubbles are caused by a combination of insufficient holding pressure, moisture and poor venting
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