Loading ...
Sorry, an error occurred while loading the content.

Re: Need some advice on making two part molds

Expand Messages
  • dkopher
    ... Took the words right off of my keyboard. Let that Vaseline/naptha mix run down the sides, all around the edges of the part. I might add one more step to
    Message 1 of 14 , Mar 30 4:33 PM
    • 0 Attachment
      --- In casting@yahoogroups.com, "Tom Banwell" <tom@l...> wrote:

      > Oops, my last post should say for step #9 (not #6).


      Took the words right off of my keyboard. Let that Vaseline/naptha mix
      run down the sides, all around the edges of the part. I might add one
      more step to the mold-making process, if you're using a tin-based RTV:
      bake the completed mold halves in a convection oven, with a tray of
      water, for about 4 hours, and let cool before beginning casting. This
      will speed-up the mold shrinkage, speed up the curing of the rubber
      and help with the out-gassing of the alcohol in the mold, (especially
      if it's a thick mold.)

      By the way, This is my first posting in this forum. I've been lurking
      for a week or so. I work as a mold maker for a rapid-prototyping
      concern.

      Dana Kopher
      Johnstown, CO
    • lewis davis
      Frances, I always use plasticine for two part moulds, some always sticks to the master no matter what release you use. I m in the UK as well, once one half of
      Message 2 of 14 , Apr 1, 2003
      • 0 Attachment
        Frances,

        I always use plasticine for two part moulds, some
        always sticks to the master no matter what release you
        use. I'm in the UK as well, once one half of the mold
        has been poured and gone off I carefully remove the
        plasticene and use white spirit to clean up the master
        and any plasticene that has stuck to the RTV being
        careful not to disturb the master. I use a soft
        paintbrush or Q-Tips. I don't have any problems with
        plasticene using this method, which makes things
        easier as its cheaper and easier to get hold of.

        Lewis

        __________________________________________________
        Yahoo! Plus
        For a better Internet experience
        http://www.yahoo.co.uk/btoffer
      • mwhirailer
        if you re using a tin-based RTV: bake the completed mold halves in a convection oven, with a tray of water, for about 4 hours, and let cool before beginning
        Message 3 of 14 , Apr 1, 2003
        • 0 Attachment
          if you're using a tin-based RTV:
          bake the completed mold halves in a convection oven, with a tray of
          water, for about 4 hours, and let cool before beginning casting. This
          will speed-up the mold shrinkage, speed up the curing of the rubber
          and help with the out-gassing of the alcohol in the mold, (especially
          if it's a thick mold.)

          Dana,

          Are you saying that by baking the curing molds in an oven for 4 hours you defeat the shrinkage on your parts? I'd heard the opposite that if you bake your mold during the cure process you'll induce shrinkage. Or am I misunderstanding you?

          Best regards,
          Terry Wellman
          St. Charles, IL

          [Non-text portions of this message have been removed]
        Your message has been successfully submitted and would be delivered to recipients shortly.