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Thread: Pin Hole in Gate

  1. #1
    Join Date
    Mar 2019
    Location
    Nebraska
    Posts
    11

    Pin Hole in Gate

    Hello all!

    Just wondering if anyone has any advice or guidance on dealing with a pin hole in the gate.

    Cavitation: 96
    Material: PET
    Hot Runner: Valve Gate

    I was inspecting tubes for bubbles when I found this defect and began to wonder the possible causes. I am new to injection molding, hence the name, and I am just starting to learn processing (with the help of Robust Process Development and Scientific Molding: Theory and Practice).

    This is my first project, and I would really like to hit a homerun! Thanks for any help.
    Attached Thumbnails Attached Thumbnails IMG_6489.jpg   IMG_6490.jpg  

  2. #2
    Join Date
    Dec 2016
    Posts
    108

    Re: Pin Hole in Gate

    Hello,

    Try, (one at a time)

    1. Slow the injection rate, as it enters the gate area
    2. More pack time
    3. Reduce Drop Temps

    Joel

  3. #3
    Join Date
    Feb 2016
    Location
    San Francisco Bay Area, CA
    Posts
    174

    Re: Pin Hole in Gate

    Yea too hot drop temps or gate temps can cause voids like that. If the material is too hot near the gate, during mold opening the material will either stick to the gate side or stick to the part side. In the case it sticks to the gate side, it can tear a void like or pin-hole like feature through your gate into your part. And by lowering your gate temps you're allowing the material to cool in that area so when mold is opened that part stays whole. At least that's how I understand the defect shown above!
    In terms of steel mods moving the drops or gate temps back away from the actual gate can help too

  4. #4
    Join Date
    Mar 2019
    Location
    Nebraska
    Posts
    11

    Re: Pin Hole in Gate

    Joel and Chris,

    Thanks for sharing! The mold is currently out for PMs, so I will give an update when we get it back in.

    Rook

  5. #5
    Join Date
    Aug 2011
    Location
    Upstate of South Carolina
    Posts
    619

    Re: Pin Hole in Gate

    Is it always the same cavity in the mold? You could have a core cooling issue at the tip. Is there water in the entire core, a bubbler or cooling pin?
    Rick

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