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Re: What to add to tubd RTV o cure it in a mold, was Re: [casting] Suppl

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  • midntr359@aol.com
    I need help setting up a molds to make parts. I ve been trying for years just can t seem to build quality parts. Air bubbles, half cast parts. I use just
    Message 1 of 3 , Feb 2, 2011
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      I need help setting up a molds to make parts. I've been trying for years
      just can't seem to build quality parts. Air bubbles, half cast parts. I
      use just Micro-Mark Resin and RTV 50/50 mix. $$$ many dollars down the drain.
      Thank you. Bill


      [Non-text portions of this message have been removed]
    • Mike Bauers
      ... At first reading, I think I see a trapped air problem that might also indicate additional vents would be the cure. Expansion voids in the molds are a good
      Message 2 of 3 , Feb 2, 2011
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        On Feb 2, 2011, at 5:55 PM, midntr359@... wrote:

        > I need help setting up a molds to make parts. I've been trying for
        > years
        > just can't seem to build quality parts. Air bubbles, half cast
        > parts. I
        > use just Micro-Mark Resin and RTV 50/50 mix. $$$ many dollars down
        > the drain.
        > Thank you. Bill

        At first reading, I think I see a trapped air problem that might also
        indicate additional vents would be the cure.

        Expansion voids in the molds are a good solution to use as well.

        This hints at needing spaces to let the lower parts of the mold
        overflow into along with extra venting to let the trapped air escape
        from lower parts of the mold.

        Can you post a couple of pictures of a problem mold and it's castings?
        You'll get specific help for that mold, that way.


        Best to ya,
        Mike Bauers
        Milwaukee, Wi
      • JCTrucks
        Hey Bill Post a pic of the master your trying to copy. I don t think anyone can help until you give us more details. Is your molds a 2 piece plunge mold or is
        Message 3 of 3 , Feb 2, 2011
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          Hey Bill



          Post a pic of the master your trying to copy.



          I don't think anyone can help until you give us more details. Is your molds a 2 piece plunge mold or is it a flat 1 piece mold? Has
          humidty contaminated your resin?

          If your mold has tight little spaces are you digging the bubbles out with a tooth pick? Are you using a pump to pump out your resin?
          If you are slow down and pump slow, this decreases the bubbles. If your using a plunge mold, give the bubbles time to surface then
          rake them off before you plunge the second mold. Are you mixing a total of 2 ounces or more when you mix your resin?



          I make HO railroad parts and HO trucks/vehicles. I have had many problems with different types of RTV and resin. If you would
          explain in more detail we should be able to help you more. Please start off with more base info about problems with RTV or do you
          think it's the resin problem.



          You stated below that "half cast parts" what do you mean? If you mean that the pull is soft or gooey then you are prolly not mixing
          A&B properly. Ratio is wrong or your mixing less than 2 ounces at a time.



          You stated below "air bubbles". In your molds or in your casting pulls? Air bubbles in your mold will cause BB's around edges on
          your pull. Air bubbles in your pull will cause hollow areas in your pull.



          We are here to help each other so feed us more info please! :-)

          Jay





          http://stores.ebay.com/World-of-JCT?refid=store

          1/87 model trucks-come join-> Subscribe: http://groups.yahoo.com/group/bigrigtrucks87/



          _____

          From: casting@yahoogroups.com [mailto:casting@yahoogroups.com] On Behalf Of Mike Bauers
          Sent: Wednesday, February 02, 2011 9:49 PM
          To: casting@yahoogroups.com
          Subject: Re: What to add to tubd RTV o cure it in a mold, was Re: [casting] Suppl





          On Feb 2, 2011, at 5:55 PM, midntr359@... <mailto:midntr359%40aol.com> wrote:

          > I need help setting up a molds to make parts. I've been trying for
          > years
          > just can't seem to build quality parts. Air bubbles, half cast
          > parts. I
          > use just Micro-Mark Resin and RTV 50/50 mix. $$$ many dollars down
          > the drain.
          > Thank you. Bill

          At first reading, I think I see a trapped air problem that might also
          indicate additional vents would be the cure.

          Expansion voids in the molds are a good solution to use as well.

          This hints at needing spaces to let the lower parts of the mold
          overflow into along with extra venting to let the trapped air escape
          from lower parts of the mold.

          Can you post a couple of pictures of a problem mold and it's castings?
          You'll get specific help for that mold, that way.

          Best to ya,
          Mike Bauers
          Milwaukee, Wi





          [Non-text portions of this message have been removed]
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