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Re: Molding small run parts

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  • Rob Goebel
    But what would you use to fill the mold? What is similar to plastic that you could mold and be affordable? My design requires a 2 piece steel mold with a
    Message 1 of 8 , Oct 1, 2008
      But what would you use to fill the mold? What is similar to plastic that you
      could mold and be affordable? My design requires a 2 piece steel mold with a
      insert for the bottom, so it basically almost a 3 sided mold to be able to
      extract the parts.

      I have made prototype parts from acrylic sheet tube and rods and glued and
      sanded everything that I can use to cast, but I don't think it will peal off
      easily.




      <http://groups.yahoo.com/group/casting/message/31428;_ylc=X3oDMTJwZW51bXVoBF
      9TAzk3MzU5NzE1BGdycElkAzIzMjA0BGdycHNwSWQDMTcwNTA2MzUxMQRtc2dJZAMzMTQyOARzZW
      MDZG1zZwRzbGsDdm1zZwRzdGltZQMxMjIyNzI1MTA0> Re: Molding small run parts

      Posted by: "Ted Quick"
      <mailto:rim_molder@...?Subject=%20Re%3A%20Molding%20small%20run%20part
      s> rim_molder@... <http://profiles.yahoo.com/rim_molder> rim_molder


      Mon Sep 29, 2008 8:59 am (PDT)

      Yes, you're definitely on the right list.

      Most people will use silicone RTV to cast a rubber mold around an existing
      part
      or a model of 1. Real question is if you have a part to start from, though
      that can be
      created or made by modifying something.

      A website that shows an example of how to do it is at:

      <http://www.danperezstudios.com/workshoppages/molding_casting.htm>
      http://www.danperezstudios.com/workshoppages/molding_casting.htm

      Ted Quick





      [Non-text portions of this message have been removed]
    • John McCann
      Look through the videos here to see if it gives you ay ideas. I m new here so I have been looking rather than doing. John
      Message 2 of 8 , Oct 1, 2008
        Look through the videos here to see if it gives you ay ideas. I'm new here
        so I have been looking rather than doing.
        John
        http://www.youtube.com/results?search_query=mold+casting&search_type=&aq=f

        ----- Original Message -----
        From: "Rob Goebel" <archeryrob@...>
        To: <casting@yahoogroups.com>
        Sent: Wednesday, October 01, 2008 7:39 AM
        Subject: [casting] Re: Molding small run parts


        But what would you use to fill the mold? What is similar to plastic that you
        could mold and be affordable? My design requires a 2 piece steel mold with a
        insert for the bottom, so it basically almost a 3 sided mold to be able to
        extract the parts.

        I have made prototype parts from acrylic sheet tube and rods and glued and
        sanded everything that I can use to cast, but I don't think it will peal off
        easily.




        <http://groups.yahoo.com/group/casting/message/31428;_ylc=X3oDMTJwZW51bXVoBF
        9TAzk3MzU5NzE1BGdycElkAzIzMjA0BGdycHNwSWQDMTcwNTA2MzUxMQRtc2dJZAMzMTQyOARzZW
        MDZG1zZwRzbGsDdm1zZwRzdGltZQMxMjIyNzI1MTA0> Re: Molding small run parts

        Posted by: "Ted Quick"
        <mailto:rim_molder@...?Subject=%20Re%3A%20Molding%20small%20run%20part
        s> rim_molder@... <http://profiles.yahoo.com/rim_molder> rim_molder


        Mon Sep 29, 2008 8:59 am (PDT)

        Yes, you're definitely on the right list.

        Most people will use silicone RTV to cast a rubber mold around an existing
        part
        or a model of 1. Real question is if you have a part to start from, though
        that can be
        created or made by modifying something.

        A website that shows an example of how to do it is at:

        <http://www.danperezstudios.com/workshoppages/molding_casting.htm>
        http://www.danperezstudios.com/workshoppages/molding_casting.htm

        Ted Quick





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


        ------------------------------------

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      • Bob Davies
        I may have missed it in an earlier posting, but depending on the size, you could make parts from polyurethene resin. If you had been considering injection
        Message 3 of 8 , Oct 1, 2008
          I may have missed it in an earlier posting, but depending on the
          size, you could make parts from polyurethene resin.

          If you had been considering injection moulding, you would need to
          ensure you have no undercuts whatsover on the mould, or you would
          need multi part moulds. You could apply the same basics to a silcon
          rubber mould and make your resin parts from it.

          Huntsman do range of resins called PIM (Parts in Minutes) which have
          to be injected to the mould, so is specialist, but should be cheaper
          than conventional injection moulding, provided you can find someone
          with the right equipement.


          --- In casting@yahoogroups.com, "Rob Goebel" <archeryrob@...> wrote:
          >
          > But what would you use to fill the mold? What is similar to plastic
          that you
          > could mold and be affordable? My design requires a 2 piece steel
          mold with a
          > insert for the bottom, so it basically almost a 3 sided mold to be
          able to
          > extract the parts.
          >
          > I have made prototype parts from acrylic sheet tube and rods and
          glued and
          > sanded everything that I can use to cast, but I don't think it will
          peal off
          > easily.
          >
          >
          >
          >
          >
          <http://groups.yahoo.com/group/casting/message/31428;_ylc=X3oDMTJwZW51
          bXVoBF
          >
          9TAzk3MzU5NzE1BGdycElkAzIzMjA0BGdycHNwSWQDMTcwNTA2MzUxMQRtc2dJZAMzMTQy
          OARzZW
          > MDZG1zZwRzbGsDdm1zZwRzdGltZQMxMjIyNzI1MTA0> Re: Molding small run
          parts
          >
          > Posted by: "Ted Quick"
          > <mailto:rim_molder@...?Subject=%20Re%3A%20Molding%20small%20run%
          20part
          > s> rim_molder@... <http://profiles.yahoo.com/rim_molder>
          rim_molder
          >
          >
          > Mon Sep 29, 2008 8:59 am (PDT)
          >
          > Yes, you're definitely on the right list.
          >
          > Most people will use silicone RTV to cast a rubber mold around an
          existing
          > part
          > or a model of 1. Real question is if you have a part to start from,
          though
          > that can be
          > created or made by modifying something.
          >
          > A website that shows an example of how to do it is at:
          >
          > <http://www.danperezstudios.com/workshoppages/molding_casting.htm>
          > http://www.danperezstudios.com/workshoppages/molding_casting.htm
          >
          > Ted Quick
          >
          >
          >
          >
          >
          > [Non-text portions of this message have been removed]
          >
        • Ted Quick
          Rob, There are several kinds of casting resins available, which are mixed in a cup and poured into a mold. You can hand cast epoxies for rigid parts,
          Message 4 of 8 , Oct 1, 2008
            Rob,

            There are several kinds of casting resins available, which are mixed in
            a cup and poured into a mold. You can hand cast epoxies
            for rigid parts, urethanes for flexible to rigid parts, or RTV silicone rubbers
            for very flexible parts. there are also polyester and vinyl ester resins, though
            these aren't usually as good, but can have specialized applications.

            Most people prefer urethanes for a "plastic" part quality, since they are more
            flexible than the all too rigid (therefore usually brittle) epoxies. Urethanes can also
            be found with a wide variety of flexibilities, from very soft flexible to fairly rigid,
            though they are all classed as elastomers.

            Using RTV silicone rubber for molds makes it possible to handle undercut areas
            that would lead to needing a 3 (or more) part steel mold. In some cases a highly
            flexible RTV mold can be made in a 1 piece "glove mold" supported by an
            epoxy "mother mold" shell to keep the mold shape while casting. That's mostly
            used for statuettes, but thought I'd mention it, never can be totally sure and it's best
            to know what might be useful.

            You say it needs an insert for the bottom, is that a mold part or something that
            stays with the part permanently?

            So, to get the resin into a mold you an pour it into the open mold cavity, then put
            the core (plug for the inside or back of the part), and push it in to compress the
            resin to force out or shrink air bubbles to leave a solid part. The core and cavity
            need to fit tightly and have a straight wall riser so that the plug will be like a piston
            in a cylinder, but of whatever shape the part requires. This would best be put
            into a pressure chamber and pressurized at 40 to 50 psi to keep the bubbles
            too small to see until the resin has set, after which they can't expand. The
            pressure chamber and an air compressor may NOT be necessary, but that
            has to be found by trial and error at first.

            In some cases it may be better to make a 2 part mold that is closed up and filled by
            pouring the resin into a "sprue" opening that leads to the bottom of the part cavity,
            often through a funnel slanted through the core to a lower corner so that the resin
            fills the cavity from the bottom up, with the air pushed out through vents to the top
            to avoid bubbles.

            Ted Quick




            ----- Original Message ----
            From: Rob Goebel <archeryrob@...>
            To: casting@yahoogroups.com
            Sent: Wednesday, October 1, 2008 10:39:40 AM
            Subject: [casting] Re: Molding small run parts


            But what would you use to fill the mold? What is similar to plastic that you
            could mold and be affordable? My design requires a 2 piece steel mold with a
            insert for the bottom, so it basically almost a 3 sided mold to be able to
            extract the parts.

            I have made prototype parts from acrylic sheet tube and rods and glued and
            sanded everything that I can use to cast, but I don't think it will peal off
            easily.

            <http://groups. yahoo.com/ group/casting/ message/31428; _ylc=X3oDMTJwZW5 1bXVoBF
            9TAzk3MzU5NzE1BGdyc ElkAzIzMjA0BGdyc HNwSWQDMTcwNTA2M zUxMQRtc2dJZAMzM TQyOARzZW
            MDZG1zZwRzbGsDdm1zZ wRzdGltZQMxMjIyN zI1MTA0> Re: Molding small run parts

            Posted by: "Ted Quick"
            <mailto:rim_molder@yahoo. com?Subject=%20Re% 3A%20Molding% 20small%20run% 20part
            s> rim_molder@yahoo. com <http://profiles. yahoo.com/ rim_molder> rim_molder

            Mon Sep 29, 2008 8:59 am (PDT)

            Yes, you're definitely on the right list.

            Most people will use silicone RTV to cast a rubber mold around an existing
            part
            or a model of 1. Real question is if you have a part to start from, though
            that can be
            created or made by modifying something.

            A website that shows an example of how to do it is at:

            <http://www.danperez studios.com/ workshoppages/ molding_casting. htm>
            http://www.danperez studios.com/ workshoppages/ molding_casting. htm

            Ted Quick

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






            [Non-text portions of this message have been removed]
          • Rob Goebel
            Thank you guys, my one part, I have several, and this one is a smaller one. It is 4 ½” tall, made of a flat riser to thin the plastic, has a ¾” pin that
            Message 5 of 8 , Oct 2, 2008
              Thank you guys, my one part, I have several, and this one is a smaller one.
              It is 4 ½” tall, made of a flat riser to thin the plastic, has a ¾” pin that
              sticks out, a hole for a screw to be set in it, a round pulley type part at
              the bottom that is 90 degrees to the top that had cut outs and webbing to
              thin the plastic and reinforce the bottom and a hole to rest on another part
              which is a pin to insert in this part. This hole requires an insert from the
              3rd section I spoke of. My original ideas was to have it made with high
              impact polystyrene as it is a hunting product and probably treated rough in
              cold weather.



              So any ideas you have that I can run with and try I would like to hear about
              them. Maybe even refer companies that it can e bought from. I tried reading
              up on the Smooth-on type stuff, but it seemed I would not get many parts
              from those expensive containers and it looked to take a lot of labor to
              produce from what I originally researched. But to attach an investor I might
              need to sell parts to be able to have the funds to produce them properly. My
              research before I did not seem to see a way to produce it to where a
              consumer could afford it from me.



              Thanks, and all help is appreciated.

              Rob



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