Direct flow visualization of hesitation during injection molding of thermoplastic polymers

Francesco Regi*, Guido Tosello

*Corresponding author for this work

    Research output: Contribution to journalConference articleResearchpeer-review

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    A special mold provided with a glass window has been used in order to directly evaluate the flow progression during the filling phase of the injection molding process. The flow of the polymer was recorded at 500 frames per second using a high-speed camera. Two unfilled thermoplastic polymers, acrylonitrile butadiene styrene (ABS) and polypropylene (PP), were used to fill a 50 mm x 18 mm staircase geometry cavity, which was specifically designed to evaluate the hesitation effects. Complete and incomplete (short shot) filling of the cavity were performed with two different velocities and with two dimensionally different but geometrically identical cavities. Two different methods for the reproduction of the short shots were used. In the first, the maximum applied pressure was limited and progressively raised (MP Method), in the second the desired positions were obtained with a consecutive increase of the stroke length (standard SS method). The analysis of the video recordings highlighted that flow progression and hesitation were mainly influenced not only by the geometry, but also by the velocity and the material.
    Original languageEnglish
    Article number030001
    JournalAIP Conference Proceedings
    Issue number1
    Number of pages5
    Publication statusPublished - 2019


    • Glass Mold
    • High Speed Camera
    • Injection Molding
    • Afterflow
    • Hesitation
    • Thermoplastic


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