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Thread: Thin wall IML defects

  1. #1
    Join Date
    Apr 2019
    Posts
    11

    Thin wall IML defects

    Hi, everyone.

    Iím having some trouble with some defects after long production runs.

    Production starts normally without an almos 0% rejection rates, but after 12 hours the rejection rate gradually keeps increasing from 1% (acceptable) to 5% (really bad) and I donít know why.
    Tried reducing the temp, increase back pressure, adjusting injection speed, injection force, rpm, increasing cooling time and it stays the same.

    Process and settings details:

    -Thin wall IML cup
    -Temp: Front 250, Middle 240, Middle 240, Back 237, Hoper OFF
    -Material PP MFR 35, with 1% titanium oxide
    -Injection speed: 210mm/s
    -Cooling 1.5s >mold temp 18C
    -Shot 71mm Ý50mm
    -Hot runner temp: 250C
    -14KGF back pressure
    -1450KGF injection force
    -160ton clamping force
    -Filling time 0.86s
    -Hold time 1s
    -Cycle time 10.8s

    Photos of the defect:
    Click image for larger version. 

Name:	4190EC0A-5888-4736-A9CB-E331B52AFB61.jpg 
Views:	37 
Size:	7.5 KB 
ID:	366
    Click image for larger version. 

Name:	4190EC0A-5888-4736-A9CB-E331B52AFB61.jpg 
Views:	37 
Size:	7.5 KB 
ID:	366
    Attached Thumbnails Attached Thumbnails A116783A-E482-44AD-AB1C-8590CBA09E12.jpg  

  2. #2
    Join Date
    Oct 2016
    Location
    McMinnville, OR
    Posts
    152

    Re: Thin wall IML defects

    I am not sure from the pictures exactly what the defect is you are having, but looks like a burn mark on the edge? If that is correct could it be that the vents on the mold are getting plugged? Do you have a set process on how often the mold is cleaned during production. If you clean the mold do the defects get better?

  3. #3
    Join Date
    Apr 2019
    Location
    Italy
    Posts
    2

    Re: Thin wall IML defects

    Hi,
    it's single cavity or multi cavities mold... where is the split line? I'm agree that seems e burn mark, so if there are propewr venting you can try to reduce clamping force. If you share more information, may be we can help you better.

  4. #4
    Join Date
    Aug 2011
    Location
    Upstate of South Carolina
    Posts
    623

    Re: Thin wall IML defects

    I’m not really getting a good feel for defect from the pictures you put up. Can you add some more and then perhaps the root cause will be clearer.
    Rick

  5. #5
    Join Date
    Apr 2019
    Posts
    11

    Re: Thin wall IML defects

    It recently came back from maintenance with and external provider and it’s the doing the same.

  6. #6
    Join Date
    Apr 2019
    Posts
    11

    Re: Thin wall IML defects

    Quote Originally Posted by daniele_66 View Post
    Hi,
    it's single cavity or multi cavities mold... where is the split line? I'm agree that seems e burn mark, so if there are propewr venting you can try to reduce clamping force. If you share more information, may be we can help you better.
    -2 cavity arranged vertically ( I don’t like the arrangement but the EOA came like that).
    -Split line located at the cup rim.
    -Reduced clamping force and it just got a really bad flash.
    -Reduced injection force and cavity It’s not filling.

  7. #7
    Join Date
    Apr 2019
    Posts
    11

    Re: Thin wall IML defects

    Quote Originally Posted by rickbatey View Post
    I’m not really getting a good feel for defect from the pictures you put up. Can you add some more and then perhaps the root cause will be clearer.
    Rick
    https://imgur.com/sXu3fdK
    https://m.imgur.com/a/gCGHOn0

    The label is destroyed at the rim, some times the label pases tru the rim.

  8. #8
    Join Date
    Aug 2011
    Location
    Upstate of South Carolina
    Posts
    623

    Re: Thin wall IML defects

    Great pics and I totally understand the issue. Iíve seen a similar problem when back molding textiles onto plastic substrates. You need to reduce the peak pressure or length of time the label sees high injection pressure in the cavity. You may even have a problem with certain cavities that points to wall thickness variations, pressure variations or core shift.
    Slightly higher barrel or maybe mold water temperatures could reduce or eliminate the defect.
    Rick.

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