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Thread: Help Troubleshooting Small Injection Mold for Small Card

  1. #1
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    Default Help Troubleshooting Small Injection Mold for Small Card

    Greetings,

    I am trying to successfully inject a mold I made for a card, but I keep getting short shots. Here is a picture of the mold and the short shot:







    I am concerned that I'm not designing the mold properly, as I'm completely self-taught. I have successfully made several other molds; however, this was the largest and thinnest I have attempted. I did some research online and found a card mold with a fan gate, so I based it off of that.

    I am using an LNS 150A (a benchtop, hand operated injection machine), and the material is ABS with a melt mass-flow rate nominal value of 21g/10 min .

    Part Size: 3" x 2" x .03"
    Vent Depth: .002"
    Fan Gate Depth: 0.0225"
    Runner Width: .25"

    I realize this part is difficult to inject largely due to it being very wide and thin, along with material's viscosity.

    Any advice would be appreciated!

    - Michael

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    Default Re: Help Troubleshooting Small Injection Mold for Small Card

    I think your fan is too far from the part and it cools too fast.
    Your melt should probably be hotter and maybe heat your mold for some better performance in a very difficult part.
    ABS is tough to use.
    I would use PP or PE. ABS doesn't really melt and will cool easier which is why it stopped flowing.
    Your mold was also probably cool and froze the flow.
    Also with the fan I would guess your 0.25 sprue doesn't feed enough material fast enough.
    If you are going to use the fan as is I would make the last 0.050" (near the part) of the fan as is and make the rest deeper to get the hot material into the cavity before it cools.



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    Default Re: Help Troubleshooting Small Injection Mold for Small Card

    Gotta get that mold HOT.



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    Default Re: Help Troubleshooting Small Injection Mold for Small Card

    I suspect... as the others said ...
    heat the mold.

    Provide more details, like always, if you want more practical advice.

    Is the material going in fast enough ?
    Are You looking for good/best quality or best time ?
    Are You looking for cycle times at all ?

    Probably, pre-heated materials and pre-heated molds, would work fine. Imho.
    Slow, per molding standards, but if you do not need production speeds..



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    Default Re: Help Troubleshooting Small Injection Mold for Small Card

    1. After doing all what was mentioned before....try using a higher flow index material, even it is not ABS just see how your part fills.
    You can get PP up to 100 flow
    These higher ABS flow materials were/are made for thin wall applications (cell phones).
    2. Put some masking tape to increase air vents at opposite from the injection point, and see what happens
    3. Make fan gate height larger than card height to have it freeze much later that it is. You will then have to cut it off with some press cutter
    4. Turn your mold design 90 degrees and inject thru the shorter side to be able to fill
    5. If you heat up the mold try going up to 100 C if necessary
    Someone mentioned they used vacuum sealed molds.
    Instead of air vents you apply a vacuum to the mold to eliminate all counter pressure from pushing the air out



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Help Troubleshooting Small Injection Mold for Small Card

Help Troubleshooting Small Injection Mold for Small Card