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Re: [casting] Misaligned mold halves....

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  • steveneserin@aol.com
    HI we vulcanise at 25t usually, we use metal hollow nuts with hexagonal surfaces. we always put a ring of them around the outside but then have two or three
    Message 1 of 17 , May 1, 2005
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      HI

      we vulcanise at 25t usually, we use metal hollow nuts with hexagonal
      surfaces. we always put a ring of them around the outside but then have two or
      three in a group in just one spot, these act as the locator and make sure the
      mold is always joined correctly.

      if the mould is slipping it is either becaus eit hasnt been completely
      vulcanised so there is some movement on the nuts, or you dont have enough pressure
      in the spin caster itself, experiment by turning up the pressure on the
      mould during casting.

      hope this helps. if not you could always get a company like ine to make
      them for you, it might be cheaper in the short term at least.

      steve
      www.thefiguretrader.co.uk


      [Non-text portions of this message have been removed]
    • firebrand100
      ... You vulcanise at 25 tons? Is that a typo? That would be about 50,000lbs (1 ton = 2000lbs) The dial on my 50ton jack only goes up to 8000lbs. What size
      Message 2 of 17 , May 1, 2005
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        --- In casting@yahoogroups.com, steveneserin@a... wrote:
        > HI
        >
        > we vulcanise at 25t usually, we use metal hollow nuts with hexagonal
        > surfaces.


        You vulcanise at 25 tons? Is that a typo? That would be about 50,000lbs
        (1 ton = 2000lbs)

        The dial on my 50ton jack only goes up to 8000lbs. What size molds are
        you making?

        Cheers,

        Rod
      • steveneserin@aol.com
        In a message dated 01/05/2005 17:28:53 GMT Standard Time, RodTyson@hotmail.com writes: You vulcanise at 25 tons? Is that a typo? That would be about 50,000lbs
        Message 3 of 17 , May 1, 2005
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          In a message dated 01/05/2005 17:28:53 GMT Standard Time,
          RodTyson@... writes:

          You vulcanise at 25 tons? Is that a typo? That would be about 50,000lbs
          (1 ton = 2000lbs)

          The dial on my 50ton jack only goes up to 8000lbs. What size molds are
          you making?




          we vulcanise at about 2500psi usually, but Im pretty sure its a 35t jack, so
          we could go alot higher. working on 9, 11 and 12 inch moulds.

          hope thats clearer.


          [Non-text portions of this message have been removed]
        • Ted Quick
          OK, you re 50 ton jack s dial only goes to 8000 lbs for a reason. The dial shows the hydraulic pressure in the pump unit, NOT the pressure as applied to the
          Message 4 of 17 , May 1, 2005
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            OK, you're 50 ton jack's dial only goes to 8000 lbs for a reason. The dial shows the hydraulic
            pressure in the pump unit, NOT the pressure as applied to the mold. When you pump it up to an
            indicated 8,000 lbs (4 tons) the larger area of the cylinder multiplies that to 50 tons. I suspect
            your cylinder is about 12.5 square inches in area (or slightly larger), which equates to an 8"
            diameter for your cylinder.

            In other words, Applied pressure=area x hydraulic pressure.

            Ted Quick
            --- firebrand100 <RodTyson@...> wrote:
            > --- In casting@yahoogroups.com, steveneserin@a... wrote:
            > > HI
            > >
            > > we vulcanise at 25t usually, we use metal hollow nuts with hexagonal
            > > surfaces.
            >
            >
            > You vulcanise at 25 tons? Is that a typo? That would be about 50,000lbs
            > (1 ton = 2000lbs)
            >
            > The dial on my 50ton jack only goes up to 8000lbs. What size molds are
            > you making?
            >
            > Cheers,
            >
            > Rod
            >
            >
            >
            >

            Ted Quick
          • Pete Brown (YahooGroups)
            Hi Ted If you don t mind me asking. I m not picturing how you use the acorn nuts. I assume you mean regular old acorn nuts like these:
            Message 5 of 17 , May 1, 2005
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              Hi Ted



              If you don't mind me asking.



              I'm not picturing how you use the acorn nuts. I assume you mean regular old
              acorn nuts like these:

              http://www.mmsacc-stainless.com/html/acorn_nuts.htm



              I've also only ever used Silicon RTV for casting, so maybe this is something
              specific to the way pressure vulcanized molds are done?



              Pete

              _____________________________________________________
              Pete Brown - Gambrills, MD (Near Annapolis)
              Visit my personal site : http://www.irritatedVowel.com
              (wallpaper, western maryland ry, .net, photography, model rr)



              _____

              From: casting@yahoogroups.com [mailto:casting@yahoogroups.com] On Behalf Of
              Ted Quick
              Sent: Saturday, April 30, 2005 11:53 PM
              To: casting@yahoogroups.com
              Subject: Re: [casting] Misaligned mold halves....



              Have you tried using acorn nuts? They just have to be planted at several
              places around the mold in
              clear areas. When the mold is formed the rubber flows up inside them and
              locks them in. The domes
              make neat holes in the other side and they are self guided when putting it
              together, since they
              don't have a square cut end. The straight up flats of the acorn nut bases
              lock the mold halves
              securely together with great accuracy.

              Ted Quick





              [Non-text portions of this message have been removed]
            • Spanosnu@aol.com
              In a message dated 5/1/2005 6:51:02 PM Eastern Standard Time, YahooLists@irritatedVowel.com writes: http://www.mmsacc-stainless.com/html/acorn_nuts.htm Pete, I
              Message 6 of 17 , May 1, 2005
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                In a message dated 5/1/2005 6:51:02 PM Eastern Standard Time,
                YahooLists@... writes:
                http://www.mmsacc-stainless.com/html/acorn_nuts.htm
                Pete,


                I went to the Acorn Nut web site. Unfortunately ther was no picture. The
                Acorn nuts I use are made from sheet metal. They are hollow and are bullet or
                acorn shaped at the top.

                They are placed on the unvulcanized disc that forms the bottom half of the
                mold after both discs have been powdered with graphite, the mold release. Both
                the patterns and the acorn nuts are positioned to suit your taste. The top
                half of the mold(adisc is then placed on ttop of the patterns and acorn nuts
                and the bottom half of the mold. The graphite keeps the two rubber discs from
                sticking to each other. The patterns do not stick to the rubber. The Acorn
                nuts do not stick to the top half of the mold, but does get fastened to the
                bottom half of the mold. Actually there is no adherance; the some of the rubber
                from the bottom half squeezes into the hollow sheet metal acorn nuts whe the
                press squezzes the two halves of the mold in the "Ring" pie mold holders.

                I have never used vulcanizing silicone rubber, altough I had several blanks
                that I never got around to trying. The silicone rubber and the two part RTV
                silicone is much softer and flexible than black vulcanizing rubber. May be that
                is the reason your mold halves shift during spincasting and mine doesn't.

                I hope this explanation helps somewhat.

                Rick Spano


                [Non-text portions of this message have been removed]
              • Pete Brown (YahooGroups)
                Hi Rick Thanks for the info If you run ZoneAlarm, you might not have seen the image. ZoneAlarm blocks lots of images on sites – it is a known bug with their
                Message 7 of 17 , May 1, 2005
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                  Hi Rick

                  Thanks for the info

                  If you run ZoneAlarm, you might not have seen the image. ZoneAlarm blocks
                  lots of images on sites – it is a known bug with their software.

                  The acorn nut on that site looks like this bad ascii art:

                  Side view (top is more rounded than I can depict here)
                  ____
                  _/____\_
                  |__|___|_|

                  Top View. Imagine a circle inside the hex here.
                  _____
                  / \
                  / \
                  \ /
                  \_____/

                  The bottom is basically just a regular threaded nut.

                  You often see them covering the ends of bolts on kid's toys, fold-up chairs
                  etc.

                  These definitely aren't sheet metal. I believe they are cast. That's good,
                  because it sounds like you're using something else than a normal acorn nut.
                  If you have a link to a photo of one, I'd love to see it.

                  I'm not the originally poster of the question about the shifting parts. My
                  apologies if I confused anyone there.

                  Pete


                  _____________________________________________________
                   Pete Brown - Gambrills, MD (Near Annapolis)
                   Visit my personal site : http://www.irritatedVowel.com
                   (wallpaper, western maryland ry, .net, photography, model rr)

                  ________________________________________
                  From: casting@yahoogroups.com [mailto:casting@yahoogroups.com] On Behalf Of
                  Spanosnu@...
                  Sent: Sunday, May 01, 2005 7:47 PM
                  To: casting@yahoogroups.com
                  Subject: Re: Acorn nuts (was RE: [casting] Misaligned mold halves....)

                  In a message dated 5/1/2005 6:51:02 PM Eastern Standard Time,
                  YahooLists@... writes:
                  http://www.mmsacc-stainless.com/html/acorn_nuts.htm
                  Pete,


                  I went to the Acorn Nut web site.  Unfortunately ther was no picture.  The
                  Acorn nuts I use are made from sheet metal.  They are hollow and are bullet
                  or
                  acorn shaped at the top.

                  They are placed on the unvulcanized disc that forms the bottom half of the
                  mold after both discs have been powdered with graphite, the mold release. 
                  Both
                  the patterns and the acorn nuts are positioned to suit your taste.   The top

                  half of the mold(adisc is then placed on ttop of the patterns and acorn nuts

                  and the bottom half of the mold.  The graphite keeps the two rubber discs
                  from
                  sticking to each other.  The patterns do not stick to the rubber.  The Acorn

                  nuts do not stick to the top half of the mold, but does get fastened to the
                  bottom half of the mold.   Actually there is no adherance; the some of the
                  rubber
                  from the bottom half squeezes into the hollow sheet metal acorn nuts whe the

                  press squezzes the two halves of the mold in the "Ring" pie mold holders.

                  I have never used vulcanizing silicone rubber, altough I had several blanks
                  that I never got around to trying.  The silicone rubber and the two part RTV

                  silicone is much softer and flexible than black vulcanizing rubber.  May be
                  that
                  is the reason your mold halves shift during spincasting and mine doesn't.

                  I hope this explanation helps somewhat.

                  Rick Spano
                • firebrand100
                  ... jack, so ... Yes - thanks Steve..:) I was going to try 2500lb - 2800lbs on my next mold.
                  Message 8 of 17 , May 1, 2005
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                    > we vulcanise at about 2500psi usually, but Im pretty sure its a 35t
                    jack, so
                    > we could go alot higher. working on 9, 11 and 12 inch moulds.
                    >
                    > hope thats clearer.


                    Yes - thanks Steve..:)

                    I was going to try 2500lb - 2800lbs on my next mold.
                  • mikefordau
                    Hello my name is Mike and I make model train parts in white metal. I make both 9 an 12 molds and have at least 12 nuts (9 mold) to tie the two halves
                    Message 9 of 17 , May 2, 2005
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                      Hello my name is Mike and I make model train parts in white metal. I
                      make both 9" an 12" molds and have at least 12 nuts (9" mold) to tie
                      the two halves together. I vulcanize at 300 for 1hr at 25 ton. I cast
                      my own nuts which are similar to an acorn nut. There can also be some
                      misalignment when casting if both halves are not kept warm at the same
                      rate. I.E. one side gets cooler if left on a cold bench while removing
                      parts from the other. The amount of pressure and rpm you cast at can
                      also have an effect if there are not enough nuts, or aren't in the
                      best place.
                    • Ted Quick
                      Oops, correction here. That would be a 4 jack diameter cylinder. ... Ted Quick
                      Message 10 of 17 , May 2, 2005
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                        Oops, correction here. That would be a 4" jack diameter cylinder.
                        --- Ted Quick <rim_molder@...> wrote:
                        > OK, you're 50 ton jack's dial only goes to 8000 lbs for a reason. The dial shows the hydraulic
                        > pressure in the pump unit, NOT the pressure as applied to the mold. When you pump it up to an
                        > indicated 8,000 lbs (4 tons) the larger area of the cylinder multiplies that to 50 tons. I
                        > suspect
                        > your cylinder is about 12.5 square inches in area (or slightly larger), which equates to an 8"
                        > diameter for your cylinder.
                        >
                        > In other words, Applied pressure=area x hydraulic pressure.
                        >
                        > Ted Quick
                        > --- firebrand100 <RodTyson@...> wrote:
                        > > --- In casting@yahoogroups.com, steveneserin@a... wrote:
                        > > > HI
                        > > >
                        > > > we vulcanise at 25t usually, we use metal hollow nuts with hexagonal
                        > > > surfaces.
                        > >
                        > >
                        > > You vulcanise at 25 tons? Is that a typo? That would be about 50,000lbs
                        > > (1 ton = 2000lbs)
                        > >
                        > > The dial on my 50ton jack only goes up to 8000lbs. What size molds are
                        > > you making?
                        > >
                        > > Cheers,
                        > >
                        > > Rod
                        > >
                        > >
                        > >
                        > >
                        >
                        > Ted Quick
                        >

                        Ted Quick
                      • Ted Quick
                        OK, those are the kind I meant. The acorn nuts are just placed on the top of the lowwer half sheet of slicinoce. It s juat a big disk, usually 1/2 thick, and
                        Message 11 of 17 , May 2, 2005
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                          OK, those are the kind I meant. The acorn nuts are just placed on the top of the lowwer half sheet
                          of slicinoce. It's juat a big disk, usually 1/2" thick, and they are piled up as needed to form
                          the lower half. Acorn nuts are placed where appropriate between cavities, talc is used as mold
                          release and dusted over the surface to form the parting line. When this is placed in side of the
                          pressure flask, which is either a ring with top and bottom plates or a pan with the bottom plate
                          and ring wall as a single piece plus a top plate. The plate(s) are set into the ring with a sheet
                          of newspaper or newsprint as a gasket in between, and the whole thing is placed in a heated press.

                          When the press is pumped up it squeezes the rubber sheetes while they are heat vulcanizing, which
                          drives out air in the mold. The air escapes through the porous newspaper without leaking out of
                          the flask.

                          Rather different from siliocne RTV. Of course the inconvenient part is that the heat cure creaates
                          shrinkage in the rubber mold which is different in 2 directions. It shrinks something like 3% in
                          height and 1.5% in width (in all flat directions), so models need to be made that account for it.

                          Ted Quick
                          --- "Pete Brown (YahooGroups)" <YahooLists@...> wrote:
                          > Hi Ted
                          > If you don't mind me asking.
                          >
                          > I'm not picturing how you use the acorn nuts. I assume you mean regular old
                          > acorn nuts like these:
                          >
                          > http://www.mmsacc-stainless.com/html/acorn_nuts.htm
                          >
                          > I've also only ever used Silicon RTV for casting, so maybe this is something
                          > specific to the way pressure vulcanized molds are done?

                          Ted Quick
                        • Pete Brown (YahooGroups)
                          Ahh ok. Thanks Ted. The disconnect for me was the whole deal with the plates. The process is totally different than RTV silicone Pete
                          Message 12 of 17 , May 2, 2005
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                            Ahh ok. Thanks Ted. The disconnect for me was the whole deal with the
                            plates. The process is totally different than RTV silicone



                            Pete



                            _____________________________________________________
                            Pete Brown - Gambrills, MD (Near Annapolis)
                            Visit my personal site : http://www.irritatedVowel.com
                            (wallpaper, western maryland ry, .net, photography, model rr)



                            _____

                            From: casting@yahoogroups.com [mailto:casting@yahoogroups.com] On Behalf Of
                            Ted Quick
                            Sent: Monday, May 02, 2005 8:17 AM
                            To: casting@yahoogroups.com
                            Subject: Re: Acorn nuts (was RE: [casting] Misaligned mold halves....)



                            OK, those are the kind I meant. The acorn nuts are just placed on the top of
                            the lowwer half sheet
                            of slicinoce. It's juat a big disk, usually 1/2" thick, and they are piled
                            up as needed to form
                            the lower half. Acorn nuts are placed where appropriate between cavities,
                            talc is used as mold
                            release and dusted over the surface to form the parting line. When this is
                            placed in side of the
                            pressure flask, which is either a ring with top and bottom plates or a pan
                            with the bottom plate
                            and ring wall as a single piece plus a top plate. The plate(s) are set into
                            the ring with a sheet
                            of newspaper or newsprint as a gasket in between, and the whole thing is
                            placed in a heated press.

                            When the press is pumped up it squeezes the rubber sheetes while they are
                            heat vulcanizing, which
                            drives out air in the mold. The air escapes through the porous newspaper
                            without leaking out of
                            the flask.

                            Rather different from siliocne RTV. Of course the inconvenient part is that
                            the heat cure creaates
                            shrinkage in the rubber mold which is different in 2 directions. It shrinks
                            something like 3% in
                            height and 1.5% in width (in all flat directions), so models need to be made
                            that account for it.

                            Ted Quick



                            [Non-text portions of this message have been removed]
                          • firebrand100
                            Thank you gentlemen for your cumulative advice and points of view. Your time is very much appreciated...:) Today I made a couple of vulcanised organic rubber
                            Message 13 of 17 , May 3, 2005
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                              Thank you gentlemen for your cumulative advice and points of view.

                              Your time is very much appreciated...:) Today I made a couple of
                              vulcanised organic rubber molds in our mold press and they have both
                              been spun cast. The results were great - and I'm very pleased. Now I
                              can press on with our other projects.
                              Last night I was about to tear my hair out...I'm sure you've all been
                              there at one time or another...:P

                              All the best,

                              Rod Tyson
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