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AU Class
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Part-Filling Issue in Injection Molding Pens-Venting Concept Development

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    In one of our projects, we encountered difficulties molding the parts due to air trap, and all of the cavities did not get filled completely. Short filling was noticed in all 64 cavities, along with flow marks. The gate location was near the core side, so the cavity side was expected to fill last. We used Moldflow software to simulate the molding scenario. With full mold setup, 64 cavities were modeled in Moldflow simulation. We noticed flow hesitation due to a drop in the temperature and pressure of the molten material. Venting was recommended to relieve the air or gas trap, and the cavity was split into two. We finalized the cavity modification drawing proposal with gas vent clearance of 0.02mm and 3mm landing. It was also suggested that we increase runner dimensions to 4mm/4.67mm to aid the flow. After tool modification, the filling results were excellent, and we achieved 100% filling. The hole that formed due to the earlier filling issue no longer exists.

    Key Learnings

    • Learn about the importance of venting in molds
    • Learn how to avoid flow marks
    • Learn about using simulation to predict failure
    • Discover causes of short fill