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Thread: Cavities blockage

  1. #1
    Join Date
    Aug 2018
    Posts
    16

    Cavities blockage

    My cap mould has been having problems , the cavities get blocked easily, some of them have 'short mould', I have been flushing it, and after 2 days 5 or 6 cavities get blocked again. The material is clean, if I increase the Injection pressure, I will start having flash. What can I do?

  2. #2
    Join Date
    Oct 2016
    Location
    McMinnville, OR
    Posts
    155

    Re: Cavities blockage

    When you are saying they get "blocked" what are they getting blocked with? That would help with troubleshooting.

  3. #3
    Join Date
    Aug 2018
    Posts
    16

    Re: Cavities blockage

    Quote Originally Posted by iautry1973 View Post
    When you are saying they get "blocked" what are they getting blocked with? That would help with troubleshooting.
    Nothing, material will just stop coming out, and the cavity will be hot, sometimes it will be forming warps

  4. #4
    Join Date
    Feb 2016
    Location
    San Francisco Bay Area, CA
    Posts
    191

    Re: Cavities blockage

    What material?
    Cold/hot runner? Hot tip cavities? Valve gate?
    Fill time? back pressure? Melt temp? Injection pressure?
    How is venting?

    Material may be freezing off or gassing out

  5. #5
    Join Date
    Aug 2011
    Location
    Upstate of South Carolina
    Posts
    651

    Re: Cavities blockage

    I’d bet it’s something in the colorant. Try running parts without color and see if it happens. Last thing you probably need a melt filter with the ability to filter particles smaller than the tips.
    Rick

  6. #6
    Join Date
    Aug 2018
    Posts
    16

    Re: Cavities blockage

    Quote Originally Posted by chrisprocess View Post
    What material?
    Cold/hot runner? Hot tip cavities? Valve gate?
    Fill time? back pressure? Melt temp? Injection pressure?
    How is venting?

    Material may be freezing off or gassing out
    HDPE, hot runner, hot tip, fill time about 12secs, melt temp - 220, pressure -75

  7. #7
    Join Date
    Aug 2018
    Posts
    16

    Re: Cavities blockage

    Quote Originally Posted by rickbatey View Post
    I’d bet it’s something in the colorant. Try running parts without color and see if it happens. Last thing you probably need a melt filter with the ability to filter particles smaller than the tips.
    Rick
    Can the colourant cause blockage?

  8. #8
    Join Date
    Nov 2012
    Posts
    101

    Re: Cavities blockage

    how big are the caps? the 12 sec inj. time for HDPE is a loooong time….

  9. #9
    Join Date
    Feb 2016
    Location
    San Francisco Bay Area, CA
    Posts
    191

    Re: Cavities blockage

    shot weight?
    12s does seem like a long time - I'm not so sure how much process control you have with this fill time

  10. #10

    Re: Cavities blockage

    Could be that you are timing out during injection. Check all heaters. Maybe take an actual "Melt Temp" reading of the material if you have the ability. Do you see fluctuations in fill time when all parts come out and when cavities are blocked? Are there differences in peak pressure at transfer?

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