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Thread: Quality Issues with Valve Gate running PC/ABS w/FR

  1. #1
    Join Date
    Sep 2012
    Location
    Lakewood, WI
    Posts
    85

    Quality Issues with Valve Gate running PC/ABS w/FR

    Struggling quite a bit with a couple molds that are valve-gated running PC/ABS w/FR. I cannot run the valve-gate temperatures at the recommended temps. without delamination, gate blush or halo appearance. But, running the temps. so low is causing leakage between the valve-gate components.

    I would take any advise anyone has, but also would like to know what experiences you have had with PC/ABS FR in valve-gate systems. I'd also like to know if there are better or worse valve-gate manufactures out there. I'm not going to mention who built this one though given we have not determined to be supplier specific.

    See attachment.
    Attached Thumbnails Attached Thumbnails Capture.JPG  

  2. #2
    Join Date
    Aug 2014
    Location
    Saint Paul, MN
    Posts
    135

    Re: Quality Issues with Valve Gate running PC/ABS w/FR

    Only thing I can suggest is make sure your valve pins have enough travel that they are not interfering with melt flow during injection.

  3. #3
    Join Date
    Aug 2011
    Location
    Upstate of South Carolina
    Posts
    597

    Re: Quality Issues with Valve Gate running PC/ABS w/FR

    If the valve gates don’t have enough cooling around them these issues can happen as well. I’d put them on tower water providing you have enough flow. If not separate them from mold base and run off water temperature controller at about 100*F. The mold steel may not have enough cooling near the drop. Use a thermal camera or contact temperature probe to confirm. The pins should be TiN coated to keep resin from sticking to them.
    Yes I prefer Synventive hot runners with or without valve gates.
    You may be causing this issue due to barrel heats. Usually with FR resins I end up with reverse barrel heat profiles and low back pressure. Most of that is FR bloom. Residence time also makes this worse.
    Now you didn’t mention these other items that may have a negative impact on your process. Are you sequential filling the part? What is the wall stock in these areas? Do you leave any vestige on the part? Are all valve gates shooting into a depression or reverse melt puddle?
    Rick.

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