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Seeking advice / guidance on parting lines.

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  • bagledman
    Hi. Have just got into making two piece moulds in RTV silicon rubber and have discovered parting lines, which isn t something I d particularly considered
    Message 1 of 13 , Jun 3, 2012
      Hi. Have just got into making two piece moulds in RTV silicon rubber and have discovered parting lines, which isn't something I'd particularly considered before.

      The project I am currently working on are small cylindrical objects about an inch long, which means the parting lines cannot be hidden within the design. I was wondering if you guys could give some practical guidance on how to minimize parting lines when casting items in two part moulds.

      On the subject of parting lines, is there a practical way of removing parting lines at the post casting stage. The material I am working with is Polytek easyflow casting plastic. I'll potentially have a couple of hundred or more of these castings, so am looking at something not too labour intensive. The onlyother material I work in is pewter,so would be appreciative of any guidance on that material too.

      Thanks in advance.

      Gem
    • Rob de Bie
      Maybe your project can be cast in a one-piece mold? I do all my parts this way, and here are some examples:
      Message 2 of 13 , Jun 3, 2012
        Maybe your project can be cast in a one-piece mold? I do all my parts
        this way, and here are some examples:

        http://robdebie.home.xs4all.nl/models/images/aqm34-32.jpg
        http://robdebie.home.xs4all.nl/models/images/tbird-12.jpg
        http://robdebie.home.xs4all.nl/models/images/e0234-13.jpg

        Rob

        At 14:31 03-06-2012, you wrote:
        >Hi. Have just got into making two piece moulds in RTV silicon
        >rubber and have discovered parting lines, which isn't something I'd
        >particularly considered before.
        >
        >The project I am currently working on are small cylindrical objects
        >about an inch long, which means the parting lines cannot be hidden
        >within the design. I was wondering if you guys could give some
        >practical guidance on how to minimize parting lines when casting
        >items in two part moulds.
        >
        >On the subject of parting lines, is there a practical way of
        >removing parting lines at the post casting stage. The material I am
        >working with is Polytek easyflow casting plastic. I'll potentially
        >have a couple of hundred or more of these castings, so am looking at
        >something not too labour intensive. The onlyother material I work
        >in is pewter,so would be appreciative of any guidance on that material too.
        >
        >Thanks in advance.
        >
        >Gem
        >
        >
        >
        >------------------------------------
        >
        >Yahoo! Groups Links
        >
        >
        >
      • Ted Quick
        Gem, Parting lines need to be placed according to which side of the part will be most visible. Since your items will be cylindrical it would be best to put the
        Message 3 of 13 , Jun 3, 2012
          Gem,


          Parting lines need to be placed according to which side of the part will be most visible. Since your items will be cylindrical it would be best to put the parting line at one end, so that the second mold half would be a core that ticks down into a hole in the mold, with the part extending inline with it. Then cleanup would amount to touching off the corner with a file, BUT that depends on just how visible that would be.

          Ted Quick



          >________________________________
          > From: bagledman <wjc@...>
          >To: casting@yahoogroups.com
          >Sent: Sunday, June 3, 2012 8:31 AM
          >Subject: [casting] Seeking advice / guidance on parting lines.
          >
          >Hi.  Have just got into making two piece moulds in RTV silicon rubber and have discovered parting lines, which isn't something I'd particularly considered before.
          >
          >The project I am currently working on are small cylindrical objects about an inch long, which means the parting lines cannot be hidden within the design.  I was wondering if you guys could give some practical guidance on how to minimize parting lines when casting items in two part moulds.
          >
          >On the subject of parting lines, is there a practical way of removing parting lines at the post casting stage.  The material I am working with is Polytek easyflow casting plastic.  I'll potentially have a couple of hundred or more of these castings, so am looking at something not too labour intensive.  The only other material I work in is pewter,so would be appreciative of any guidance on that material too.
          >
          >Thanks in
          advance.
          >
          >Gem
          >
          >
          >
          >------------------------------------
          >
          >Yahoo! Groups Links
          >
          >
          >
          >
          >
          >

          [Non-text portions of this message have been removed]
        • bagledman
          Thanks Ted. I guess it all comes down planning where to hide the pating lines before you even contemplate building the moulds then. Certainly something to
          Message 4 of 13 , Jun 3, 2012
            Thanks Ted. I guess it all comes down planning where to hide the pating lines before you even contemplate building the moulds then. Certainly something to delve further into.

            The cylinders will be in a display environment so I would ideally like to keep the parting lines out of sight. Somehow getting them on the end seems more logical.

            Thanks again.

            Gem

            --- In casting@yahoogroups.com, Ted Quick <rim_molder@...> wrote:
            >
            > Gem,
            >
            >
            > Parting lines need to be placed according to which side of the part will be most visible. Since your items will be cylindrical it would be best to put the parting line at one end, so that the second mold half would be a core that ticks down into a hole in the mold, with the part extending inline with it. Then cleanup would amount to touching off the corner with a file, BUT that depends on just how visible that would be.
            >
            > Ted Quick
            >
            >
            >
            > >________________________________
            > > From: bagledman <wjc@...>
            > >To: casting@yahoogroups.com
            > >Sent: Sunday, June 3, 2012 8:31 AM
            > >Subject: [casting] Seeking advice / guidance on parting lines.
            > >
            > >Hi.  Have just got into making two piece moulds in RTV silicon rubber and have discovered parting lines, which isn't something I'd particularly considered before.
            > >
            > >The project I am currently working on are small cylindrical objects about an inch long, which means the parting lines cannot be hidden within the design.  I was wondering if you guys could give some practical guidance on how to minimize parting lines when casting items in two part moulds.
            > >
            > >On the subject of parting lines, is there a practical way of removing parting lines at the post casting stage.  The material I am working with is Polytek easyflow casting plastic.  I'll potentially have a couple of hundred or more of these castings, so am looking at something not too labour intensive.  The only other material I work in is pewter,so would be appreciative of any guidance on that material too.
            > >
            > >Thanks in
            > advance.
            > >
            > >Gem
            > >
            > >
            > >
            > >------------------------------------
            > >
            > >Yahoo! Groups Links
            > >
            > >
            > >
            > >
            > >
            > >
            >
            > [Non-text portions of this message have been removed]
            >
          • bagledman
            I did have a single attempt at a one piece mould Rob, but ended up with an ellipse rather than a truly circular cylinder :-( I found myself having to slit the
            Message 5 of 13 , Jun 3, 2012
              I did have a single attempt at a one piece mould Rob, but ended up with an ellipse rather than a truly circular cylinder :-( I found myself having to slit the one piece mould down about three quarters of its depth to be able to extract the component.

              As I am planning to eventually use the home made centrifugal caster I have to give optimum results, my preference is ideally for a two piece mould. The castings in your posting look extremely good though.

              Out of curiosity how do you manage to manage to design your one piece moulds to minimise post casting finishing? Last time I casted a figurine with a one piece latex mould (few years ago), I remember having to invest a large amount of time to get the base flat, post pouring.

              Thanks

              Gem


              --- In casting@yahoogroups.com, Rob de Bie <robdebie@...> wrote:
              >
              > Maybe your project can be cast in a one-piece mold? I do all my parts
              > this way, and here are some examples:
              >
              > http://robdebie.home.xs4all.nl/models/images/aqm34-32.jpg
              > http://robdebie.home.xs4all.nl/models/images/tbird-12.jpg
              > http://robdebie.home.xs4all.nl/models/images/e0234-13.jpg
              >
              > Rob
              >
              > At 14:31 03-06-2012, you wrote:
              > >Hi. Have just got into making two piece moulds in RTV silicon
              > >rubber and have discovered parting lines, which isn't something I'd
              > >particularly considered before.
              > >
              > >The project I am currently working on are small cylindrical objects
              > >about an inch long, which means the parting lines cannot be hidden
              > >within the design. I was wondering if you guys could give some
              > >practical guidance on how to minimize parting lines when casting
              > >items in two part moulds.
              > >
              > >On the subject of parting lines, is there a practical way of
              > >removing parting lines at the post casting stage. The material I am
              > >working with is Polytek easyflow casting plastic. I'll potentially
              > >have a couple of hundred or more of these castings, so am looking at
              > >something not too labour intensive. The onlyother material I work
              > >in is pewter,so would be appreciative of any guidance on that material too.
              > >
              > >Thanks in advance.
              > >
              > >Gem
              > >
              > >
              > >
              > >------------------------------------
              > >
              > >Yahoo! Groups Links
              > >
              > >
              > >
              >
            • Rob de Bie
              I use very soft silicone rubber, 10 Shore, and this allows undercuts that are almost silly. About the design: these days I always use a rectangular block of
              Message 6 of 13 , Jun 3, 2012
                I use very soft silicone rubber, 10 Shore, and this allows undercuts
                that are almost silly. About the design: these days I always use a
                rectangular block of plastic and thin plastic card to connect the
                block to the master part. After pouring the mold, the rectangular
                block forms the resin cavity. I don't have a photo of this stage, but
                this photo of a mold plus products will also show what I mean:

                http://robdebie.home.xs4all.nl/models/images/aqm34-29.jpg

                If you want the casting to have a base that's flat on the lower side,
                I would fill the mold's resin cavity completely and then a little
                more, and drop a waxed flat piece (glass, sheet metal, plastic) on it.

                Rob

                At 20:53 03-06-2012, you wrote:
                >I did have a single attempt at a one piece mould Rob, but ended up
                >with an ellipse rather than a truly circular cylinder :-( I found
                >myself having to slit the one piece mould down about three quarters
                >of its depth to be able to extract the component.
                >
                >As I am planning to eventually use the home made centrifugal caster
                >I have to give optimum results, my preference is ideally for a two
                >piece mould. The castings in your posting look extremely good though.
                >
                >Out of curiosity how do you manage to manage to design your one
                >piece moulds to minimise post casting finishing? Last time I casted
                >a figurine with a one piece latex mould (few years ago), I remember
                >having to invest a large amount of time to get the base flat, post pouring.
                >
                >Thanks
                >
                >Gem
                >
                >
                >--- In casting@yahoogroups.com, Rob de Bie <robdebie@...> wrote:
                > >
                > > Maybe your project can be cast in a one-piece mold? I do all my parts
                > > this way, and here are some examples:
                > >
                > > http://robdebie.home.xs4all.nl/models/images/aqm34-32.jpg
                > > http://robdebie.home.xs4all.nl/models/images/tbird-12.jpg
                > > http://robdebie.home.xs4all.nl/models/images/e0234-13.jpg
                > >
                > > Rob
                > >
                > > At 14:31 03-06-2012, you wrote:
                > > >Hi. Have just got into making two piece moulds in RTV silicon
                > > >rubber and have discovered parting lines, which isn't something I'd
                > > >particularly considered before.
                > > >
                > > >The project I am currently working on are small cylindrical objects
                > > >about an inch long, which means the parting lines cannot be hidden
                > > >within the design. I was wondering if you guys could give some
                > > >practical guidance on how to minimize parting lines when casting
                > > >items in two part moulds.
                > > >
                > > >On the subject of parting lines, is there a practical way of
                > > >removing parting lines at the post casting stage. The material I am
                > > >working with is Polytek easyflow casting plastic. I'll potentially
                > > >have a couple of hundred or more of these castings, so am looking at
                > > >something not too labour intensive. The onlyother material I work
                > > >in is pewter,so would be appreciative of any guidance on that
                > material too.
                > > >
                > > >Thanks in advance.
                > > >
                > > >Gem
                > > >
                > > >
                > > >
                > > >------------------------------------
                > > >
                > > >Yahoo! Groups Links
                > > >
                > > >
                > > >
                > >
                >
                >
                >
                >
                >------------------------------------
                >
                >Yahoo! Groups Links
                >
                >
                >
              • bagledman
                Thanks for the extra info Rob. A different grade of rubber is certainly something I will try out in my experiments. The waxed flat sheet is a good tip to
                Message 7 of 13 , Jun 3, 2012
                  Thanks for the extra info Rob. A different grade of rubber is certainly something I will try out in my experiments. The waxed flat sheet is a good tip to minimise the sanding and polishing.

                  Gem


                  --- In casting@yahoogroups.com, Rob de Bie <robdebie@...> wrote:
                  >
                  > I use very soft silicone rubber, 10 Shore, and this allows undercuts
                  > that are almost silly. About the design: these days I always use a
                  > rectangular block of plastic and thin plastic card to connect the
                  > block to the master part. After pouring the mold, the rectangular
                  > block forms the resin cavity. I don't have a photo of this stage, but
                  > this photo of a mold plus products will also show what I mean:
                  >
                  > http://robdebie.home.xs4all.nl/models/images/aqm34-29.jpg
                  >
                  > If you want the casting to have a base that's flat on the lower side,
                  > I would fill the mold's resin cavity completely and then a little
                  > more, and drop a waxed flat piece (glass, sheet metal, plastic) on it.
                  >
                  > Rob
                  >
                  > At 20:53 03-06-2012, you wrote:
                  > >I did have a single attempt at a one piece mould Rob, but ended up
                  > >with an ellipse rather than a truly circular cylinder :-( I found
                  > >myself having to slit the one piece mould down about three quarters
                  > >of its depth to be able to extract the component.
                  > >
                  > >As I am planning to eventually use the home made centrifugal caster
                  > >I have to give optimum results, my preference is ideally for a two
                  > >piece mould. The castings in your posting look extremely good though.
                  > >
                  > >Out of curiosity how do you manage to manage to design your one
                  > >piece moulds to minimise post casting finishing? Last time I casted
                  > >a figurine with a one piece latex mould (few years ago), I remember
                  > >having to invest a large amount of time to get the base flat, post pouring.
                  > >
                  > >Thanks
                  > >
                  > >Gem
                  > >
                  > >
                  > >--- In casting@yahoogroups.com, Rob de Bie <robdebie@> wrote:
                  > > >
                  > > > Maybe your project can be cast in a one-piece mold? I do all my parts
                  > > > this way, and here are some examples:
                  > > >
                  > > > http://robdebie.home.xs4all.nl/models/images/aqm34-32.jpg
                  > > > http://robdebie.home.xs4all.nl/models/images/tbird-12.jpg
                  > > > http://robdebie.home.xs4all.nl/models/images/e0234-13.jpg
                  > > >
                  > > > Rob
                  > > >
                  > > > At 14:31 03-06-2012, you wrote:
                  > > > >Hi. Have just got into making two piece moulds in RTV silicon
                  > > > >rubber and have discovered parting lines, which isn't something I'd
                  > > > >particularly considered before.
                  > > > >
                  > > > >The project I am currently working on are small cylindrical objects
                  > > > >about an inch long, which means the parting lines cannot be hidden
                  > > > >within the design. I was wondering if you guys could give some
                  > > > >practical guidance on how to minimize parting lines when casting
                  > > > >items in two part moulds.
                  > > > >
                  > > > >On the subject of parting lines, is there a practical way of
                  > > > >removing parting lines at the post casting stage. The material I am
                  > > > >working with is Polytek easyflow casting plastic. I'll potentially
                  > > > >have a couple of hundred or more of these castings, so am looking at
                  > > > >something not too labour intensive. The onlyother material I work
                  > > > >in is pewter,so would be appreciative of any guidance on that
                  > > material too.
                  > > > >
                  > > > >Thanks in advance.
                  > > > >
                  > > > >Gem
                  > > > >
                  > > > >
                  > > > >
                  > > > >------------------------------------
                  > > > >
                  > > > >Yahoo! Groups Links
                  > > > >
                  > > > >
                  > > > >
                  > > >
                  > >
                  > >
                  > >
                  > >
                  > >------------------------------------
                  > >
                  > >Yahoo! Groups Links
                  > >
                  > >
                  > >
                  >
                • Ainsley Israel
                  What sort of rubber do you use rob, I would like to give it a try. I have a job which has several large undercuts; I have been racking my brain to workout how
                  Message 8 of 13 , Jun 3, 2012
                    What sort of rubber do you use rob, I would like to give it a try.

                    I have a job which has several large undercuts; I have been racking my brain
                    to workout how to do it.

                    Didn't think of softer rubber.

                    Ainsley



                    _____

                    From: casting@yahoogroups.com [mailto:casting@yahoogroups.com] On Behalf Of
                    Rob de Bie
                    Sent: Monday, 4 June 2012 5:35 AM
                    To: casting@yahoogroups.com
                    Subject: Re: [casting] Re: Seeking advice / guidance on parting lines.





                    I use very soft silicone rubber, 10 Shore, and this allows undercuts
                    that are almost silly. About the design: these days I always use a
                    rectangular block of plastic and thin plastic card to connect the
                    block to the master part. After pouring the mold, the rectangular
                    block forms the resin cavity. I don't have a photo of this stage, but
                    this photo of a mold plus products will also show what I mean:

                    http://robdebie.home.xs4all.nl/models/images/aqm34-29.jpg

                    If you want the casting to have a base that's flat on the lower side,
                    I would fill the mold's resin cavity completely and then a little
                    more, and drop a waxed flat piece (glass, sheet metal, plastic) on it.

                    Rob

                    At 20:53 03-06-2012, you wrote:
                    >I did have a single attempt at a one piece mould Rob, but ended up
                    >with an ellipse rather than a truly circular cylinder :-( I found
                    >myself having to slit the one piece mould down about three quarters
                    >of its depth to be able to extract the component.
                    >
                    >As I am planning to eventually use the home made centrifugal caster
                    >I have to give optimum results, my preference is ideally for a two
                    >piece mould. The castings in your posting look extremely good though.
                    >
                    >Out of curiosity how do you manage to manage to design your one
                    >piece moulds to minimise post casting finishing? Last time I casted
                    >a figurine with a one piece latex mould (few years ago), I remember
                    >having to invest a large amount of time to get the base flat, post pouring.
                    >
                    >Thanks
                    >
                    >Gem
                    >
                    >
                    >--- In casting@yahoogroups.com <mailto:casting%40yahoogroups.com> , Rob de
                    Bie <robdebie@...> wrote:
                    > >
                    > > Maybe your project can be cast in a one-piece mold? I do all my parts
                    > > this way, and here are some examples:
                    > >
                    > > http://robdebie.home.xs4all.nl/models/images/aqm34-32.jpg
                    > > http://robdebie.home.xs4all.nl/models/images/tbird-12.jpg
                    > > http://robdebie.home.xs4all.nl/models/images/e0234-13.jpg
                    > >
                    > > Rob
                    > >
                    > > At 14:31 03-06-2012, you wrote:
                    > > >Hi. Have just got into making two piece moulds in RTV silicon
                    > > >rubber and have discovered parting lines, which isn't something I'd
                    > > >particularly considered before.
                    > > >
                    > > >The project I am currently working on are small cylindrical objects
                    > > >about an inch long, which means the parting lines cannot be hidden
                    > > >within the design. I was wondering if you guys could give some
                    > > >practical guidance on how to minimize parting lines when casting
                    > > >items in two part moulds.
                    > > >
                    > > >On the subject of parting lines, is there a practical way of
                    > > >removing parting lines at the post casting stage. The material I am
                    > > >working with is Polytek easyflow casting plastic. I'll potentially
                    > > >have a couple of hundred or more of these castings, so am looking at
                    > > >something not too labour intensive. The onlyother material I work
                    > > >in is pewter,so would be appreciative of any guidance on that
                    > material too.
                    > > >
                    > > >Thanks in advance.
                    > > >
                    > > >Gem
                    > > >
                    > > >
                    > > >
                    > > >------------------------------------
                    > > >
                    > > >Yahoo! Groups Links
                    > > >
                    > > >
                    > > >
                    > >
                    >
                    >
                    >
                    >
                    >------------------------------------
                    >
                    >Yahoo! Groups Links
                    >
                    >
                    >





                    [Non-text portions of this message have been removed]
                  • Charles Anderson
                    ... Hi Gem, Even in a cylinder there will be parting lines, however, it depends on how complex the cylinders are. I mostly do metal casting, but I do make
                    Message 9 of 13 , Jun 3, 2012
                      On 3/06/2012 10:31 PM, bagledman wrote:
                      > Hi. Have just got into making two piece moulds in RTV silicon rubber and have discovered parting lines, which isn't something I'd particularly considered before.
                      >
                      > The project I am currently working on are small cylindrical objects about an inch long, which means the parting lines cannot be hidden within the design. I was wondering if you guys could give some practical guidance on how to minimize parting lines when casting items in two part moulds.
                      >
                      > On the subject of parting lines, is there a practical way of removing parting lines at the post casting stage. The material I am working with is Polytek easyflow casting plastic. I'll potentially have a couple of hundred or more of these castings, so am looking at something not too labour intensive. The onlyother material I work in is pewter,so would be appreciative of any guidance on that material too.
                      >
                      > Thanks in advance.
                      >
                      > Gem

                      Hi Gem,

                      Even in a cylinder there will be parting lines, however, it depends on
                      how complex the cylinders are.

                      I mostly do metal casting, but I do make cylinders out of precious
                      metals so that I can make wire.

                      If the cylinder is not attached to anything, there's is no reason why
                      you can't make an uninterrupted tube and have the parting lines on the
                      top and bottom of the cylinder.


                      Regards Charles from Oz
                    • bagledman
                      Unfortunately Charles there is more complexity to the cylinders with there being a small small structural stub on one end and a shallow internal thread on the
                      Message 10 of 13 , Jun 4, 2012
                        Unfortunately Charles there is more complexity to the cylinders with there being a small small structural stub on one end and a shallow internal thread on the other end. To use a continuous cylinder would mean drilling with two different size drills and putting a shallow tap on one end. The casting works out ok, but just need to hide the parting lines to make the item more aesthetic :-)

                        Ideally I would have liked to use centrifugal casting for these items, but guess I will have to go for gravity casting with a vibratory table to get the parting lines at the ends.

                        Thanks.

                        Gem


                        --- In casting@yahoogroups.com, Charles Anderson <charlesanderson@...> wrote:
                        >
                        > On 3/06/2012 10:31 PM, bagledman wrote:
                        > > Hi. Have just got into making two piece moulds in RTV silicon rubber and have discovered parting lines, which isn't something I'd particularly considered before.
                        > >
                        > > The project I am currently working on are small cylindrical objects about an inch long, which means the parting lines cannot be hidden within the design. I was wondering if you guys could give some practical guidance on how to minimize parting lines when casting items in two part moulds.
                        > >
                        > > On the subject of parting lines, is there a practical way of removing parting lines at the post casting stage. The material I am working with is Polytek easyflow casting plastic. I'll potentially have a couple of hundred or more of these castings, so am looking at something not too labour intensive. The onlyother material I work in is pewter,so would be appreciative of any guidance on that material too.
                        > >
                        > > Thanks in advance.
                        > >
                        > > Gem
                        >
                        > Hi Gem,
                        >
                        > Even in a cylinder there will be parting lines, however, it depends on
                        > how complex the cylinders are.
                        >
                        > I mostly do metal casting, but I do make cylinders out of precious
                        > metals so that I can make wire.
                        >
                        > If the cylinder is not attached to anything, there's is no reason why
                        > you can't make an uninterrupted tube and have the parting lines on the
                        > top and bottom of the cylinder.
                        >
                        >
                        > Regards Charles from Oz
                        >
                      • Rob de Bie
                        It s a local brand, probably repackaged: http://www.polyservice.nl/Siliconenrubber-PS-8510--set-2-kg-p-16281.html Main characteristics are 10 Shore-A, addition
                        Message 11 of 13 , Jun 7, 2012
                          It's a local brand, probably repackaged:

                          http://www.polyservice.nl/Siliconenrubber-PS-8510--set-2-kg-p-16281.html

                          Main characteristics are 10 Shore-A, addition / platinum cure, 5000
                          mPa.s viscoity (i.e. thin), pot life 15 minutes, cure time 2-3 hours.
                          My last set lasted four years, which I think is impressive for
                          silicone rubber. It has the perfect combination of specs for my
                          purposes! The only thing I don't know yet is how many polyurethane
                          castings I can pull from a mould.

                          Rob

                          At 23:49 03-06-2012, you wrote:
                          >What sort of rubber do you use rob, I would like to give it a try.
                          >
                          >I have a job which has several large undercuts; I have been racking my brain
                          >to workout how to do it.
                          >
                          >Didn't think of softer rubber.
                          >
                          >Ainsley
                          >
                          >
                          >
                          > _____
                          >
                          >From: casting@yahoogroups.com [mailto:casting@yahoogroups.com] On Behalf Of
                          >Rob de Bie
                          >Sent: Monday, 4 June 2012 5:35 AM
                          >To: casting@yahoogroups.com
                          >Subject: Re: [casting] Re: Seeking advice / guidance on parting lines.
                          >
                          >
                          >
                          >
                          >
                          >I use very soft silicone rubber, 10 Shore, and this allows undercuts
                          >that are almost silly. About the design: these days I always use a
                          >rectangular block of plastic and thin plastic card to connect the
                          >block to the master part. After pouring the mold, the rectangular
                          >block forms the resin cavity. I don't have a photo of this stage, but
                          >this photo of a mold plus products will also show what I mean:
                          >
                          >http://robdebie.home.xs4all.nl/models/images/aqm34-29.jpg
                          >
                          >If you want the casting to have a base that's flat on the lower side,
                          >I would fill the mold's resin cavity completely and then a little
                          >more, and drop a waxed flat piece (glass, sheet metal, plastic) on it.
                          >
                          >Rob
                          >
                          >At 20:53 03-06-2012, you wrote:
                          > >I did have a single attempt at a one piece mould Rob, but ended up
                          > >with an ellipse rather than a truly circular cylinder :-( I found
                          > >myself having to slit the one piece mould down about three quarters
                          > >of its depth to be able to extract the component.
                          > >
                          > >As I am planning to eventually use the home made centrifugal caster
                          > >I have to give optimum results, my preference is ideally for a two
                          > >piece mould. The castings in your posting look extremely good though.
                          > >
                          > >Out of curiosity how do you manage to manage to design your one
                          > >piece moulds to minimise post casting finishing? Last time I casted
                          > >a figurine with a one piece latex mould (few years ago), I remember
                          > >having to invest a large amount of time to get the base flat, post pouring.
                          > >
                          > >Thanks
                          > >
                          > >Gem
                          > >
                          > >
                          > >--- In casting@yahoogroups.com <mailto:casting%40yahoogroups.com> , Rob de
                          >Bie <robdebie@...> wrote:
                          > > >
                          > > > Maybe your project can be cast in a one-piece mold? I do all my parts
                          > > > this way, and here are some examples:
                          > > >
                          > > > http://robdebie.home.xs4all.nl/models/images/aqm34-32.jpg
                          > > > http://robdebie.home.xs4all.nl/models/images/tbird-12.jpg
                          > > > http://robdebie.home.xs4all.nl/models/images/e0234-13.jpg
                          > > >
                          > > > Rob
                          > > >
                          > > > At 14:31 03-06-2012, you wrote:
                          > > > >Hi. Have just got into making two piece moulds in RTV silicon
                          > > > >rubber and have discovered parting lines, which isn't something I'd
                          > > > >particularly considered before.
                          > > > >
                          > > > >The project I am currently working on are small cylindrical objects
                          > > > >about an inch long, which means the parting lines cannot be hidden
                          > > > >within the design. I was wondering if you guys could give some
                          > > > >practical guidance on how to minimize parting lines when casting
                          > > > >items in two part moulds.
                          > > > >
                          > > > >On the subject of parting lines, is there a practical way of
                          > > > >removing parting lines at the post casting stage. The material I am
                          > > > >working with is Polytek easyflow casting plastic. I'll potentially
                          > > > >have a couple of hundred or more of these castings, so am looking at
                          > > > >something not too labour intensive. The onlyother material I work
                          > > > >in is pewter,so would be appreciative of any guidance on that
                          > > material too.
                          > > > >
                          > > > >Thanks in advance.
                          > > > >
                          > > > >Gem
                          > > > >
                          > > > >
                          > > > >
                          > > > >------------------------------------
                          > > > >
                          > > > >Yahoo! Groups Links
                          > > > >
                          > > > >
                          > > > >
                          > > >
                          > >
                          > >
                          > >
                          > >
                          > >------------------------------------
                          > >
                          > >Yahoo! Groups Links
                          > >
                          > >
                          > >
                          >
                          >
                          >
                          >
                          >
                          >[Non-text portions of this message have been removed]
                          >
                          >
                          >
                          >------------------------------------
                          >
                          >Yahoo! Groups Links
                          >
                          >
                          >
                        • Ainsley Israel
                          That s great, Do use commercial release agent? I used to, however I struggled with mold degradation. I have now been using baby powder and it is awesome. No
                          Message 12 of 13 , Jun 7, 2012
                            That's great,

                            Do use commercial release agent? I used to, however I struggled with mold
                            degradation.

                            I have now been using baby powder and it is awesome. No degradation at all.

                            Ainsley



                            _____

                            From: casting@yahoogroups.com [mailto:casting@yahoogroups.com] On Behalf Of
                            Rob de Bie
                            Sent: Friday, 8 June 2012 7:56 AM
                            To: casting@yahoogroups.com
                            Subject: RE: [casting] Re: Seeking advice / guidance on parting lines.





                            It's a local brand, probably repackaged:

                            http://www.polyservice.nl/Siliconenrubber-PS-8510--set-2-kg-p-16281.html

                            Main characteristics are 10 Shore-A, addition / platinum cure, 5000
                            mPa.s viscoity (i.e. thin), pot life 15 minutes, cure time 2-3 hours.
                            My last set lasted four years, which I think is impressive for
                            silicone rubber. It has the perfect combination of specs for my
                            purposes! The only thing I don't know yet is how many polyurethane
                            castings I can pull from a mould.

                            Rob

                            At 23:49 03-06-2012, you wrote:
                            >What sort of rubber do you use rob, I would like to give it a try.
                            >
                            >I have a job which has several large undercuts; I have been racking my
                            brain
                            >to workout how to do it.
                            >
                            >Didn't think of softer rubber.
                            >
                            >Ainsley
                            >
                            >
                            >
                            > _____
                            >
                            >From: casting@yahoogroups.com <mailto:casting%40yahoogroups.com>
                            [mailto:casting@yahoogroups.com <mailto:casting%40yahoogroups.com> ] On
                            Behalf Of
                            >Rob de Bie
                            >Sent: Monday, 4 June 2012 5:35 AM
                            >To: casting@yahoogroups.com <mailto:casting%40yahoogroups.com>
                            >Subject: Re: [casting] Re: Seeking advice / guidance on parting lines.
                            >
                            >
                            >
                            >
                            >
                            >I use very soft silicone rubber, 10 Shore, and this allows undercuts
                            >that are almost silly. About the design: these days I always use a
                            >rectangular block of plastic and thin plastic card to connect the
                            >block to the master part. After pouring the mold, the rectangular
                            >block forms the resin cavity. I don't have a photo of this stage, but
                            >this photo of a mold plus products will also show what I mean:
                            >
                            >http://robdebie.home.xs4all.nl/models/images/aqm34-29.jpg
                            >
                            >If you want the casting to have a base that's flat on the lower side,
                            >I would fill the mold's resin cavity completely and then a little
                            >more, and drop a waxed flat piece (glass, sheet metal, plastic) on it.
                            >
                            >Rob
                            >
                            >At 20:53 03-06-2012, you wrote:
                            > >I did have a single attempt at a one piece mould Rob, but ended up
                            > >with an ellipse rather than a truly circular cylinder :-( I found
                            > >myself having to slit the one piece mould down about three quarters
                            > >of its depth to be able to extract the component.
                            > >
                            > >As I am planning to eventually use the home made centrifugal caster
                            > >I have to give optimum results, my preference is ideally for a two
                            > >piece mould. The castings in your posting look extremely good though.
                            > >
                            > >Out of curiosity how do you manage to manage to design your one
                            > >piece moulds to minimise post casting finishing? Last time I casted
                            > >a figurine with a one piece latex mould (few years ago), I remember
                            > >having to invest a large amount of time to get the base flat, post
                            pouring.
                            > >
                            > >Thanks
                            > >
                            > >Gem
                            > >
                            > >
                            > >--- In casting@yahoogroups.com <mailto:casting%40yahoogroups.com>
                            <mailto:casting%40yahoogroups.com> , Rob de
                            >Bie <robdebie@...> wrote:
                            > > >
                            > > > Maybe your project can be cast in a one-piece mold? I do all my parts
                            > > > this way, and here are some examples:
                            > > >
                            > > > http://robdebie.home.xs4all.nl/models/images/aqm34-32.jpg
                            > > > http://robdebie.home.xs4all.nl/models/images/tbird-12.jpg
                            > > > http://robdebie.home.xs4all.nl/models/images/e0234-13.jpg
                            > > >
                            > > > Rob
                            > > >
                            > > > At 14:31 03-06-2012, you wrote:
                            > > > >Hi. Have just got into making two piece moulds in RTV silicon
                            > > > >rubber and have discovered parting lines, which isn't something I'd
                            > > > >particularly considered before.
                            > > > >
                            > > > >The project I am currently working on are small cylindrical objects
                            > > > >about an inch long, which means the parting lines cannot be hidden
                            > > > >within the design. I was wondering if you guys could give some
                            > > > >practical guidance on how to minimize parting lines when casting
                            > > > >items in two part moulds.
                            > > > >
                            > > > >On the subject of parting lines, is there a practical way of
                            > > > >removing parting lines at the post casting stage. The material I am
                            > > > >working with is Polytek easyflow casting plastic. I'll potentially
                            > > > >have a couple of hundred or more of these castings, so am looking at
                            > > > >something not too labour intensive. The onlyother material I work
                            > > > >in is pewter,so would be appreciative of any guidance on that
                            > > material too.
                            > > > >
                            > > > >Thanks in advance.
                            > > > >
                            > > > >Gem
                            > > > >
                            > > > >
                            > > > >
                            > > > >------------------------------------
                            > > > >
                            > > > >Yahoo! Groups Links
                            > > > >
                            > > > >
                            > > > >
                            > > >
                            > >
                            > >
                            > >
                            > >
                            > >------------------------------------
                            > >
                            > >Yahoo! Groups Links
                            > >
                            > >
                            > >
                            >
                            >
                            >
                            >
                            >
                            >[Non-text portions of this message have been removed]
                            >
                            >
                            >
                            >------------------------------------
                            >
                            >Yahoo! Groups Links
                            >
                            >
                            >





                            [Non-text portions of this message have been removed]
                          • Rob de Bie
                            I never use release agent, because so far I never cast large numbers of parts from one mould, and because I really don t like traces of release agent left on
                            Message 13 of 13 , Jun 8, 2012
                              I never use release agent, because so far I never cast large numbers
                              of parts from one mould, and because I really don't like traces of
                              release agent left on the cast parts. Also, with the small and
                              detailed moulds that I use, I don't see how I can get release agent
                              in all nooks and crannies. Rather I would cast a new mould after x
                              pulls. In my case that's easy, cheap and quick.

                              Rob

                              At 01:53 08-06-2012, you wrote:
                              >That's great,
                              >
                              >Do use commercial release agent? I used to, however I struggled with mold
                              >degradation.
                              >
                              >I have now been using baby powder and it is awesome. No degradation at all.
                              >
                              >Ainsley
                              >
                              >
                              >
                              > _____
                              >
                              >From: casting@yahoogroups.com [mailto:casting@yahoogroups.com] On Behalf Of
                              >Rob de Bie
                              >Sent: Friday, 8 June 2012 7:56 AM
                              >To: casting@yahoogroups.com
                              >Subject: RE: [casting] Re: Seeking advice / guidance on parting lines.
                              >
                              >
                              >
                              >
                              >
                              >It's a local brand, probably repackaged:
                              >
                              >http://www.polyservice.nl/Siliconenrubber-PS-8510--set-2-kg-p-16281.html
                              >
                              >Main characteristics are 10 Shore-A, addition / platinum cure, 5000
                              >mPa.s viscoity (i.e. thin), pot life 15 minutes, cure time 2-3 hours.
                              >My last set lasted four years, which I think is impressive for
                              >silicone rubber. It has the perfect combination of specs for my
                              >purposes! The only thing I don't know yet is how many polyurethane
                              >castings I can pull from a mould.
                              >
                              >Rob
                              >
                              >At 23:49 03-06-2012, you wrote:
                              > >What sort of rubber do you use rob, I would like to give it a try.
                              > >
                              > >I have a job which has several large undercuts; I have been racking my
                              >brain
                              > >to workout how to do it.
                              > >
                              > >Didn't think of softer rubber.
                              > >
                              > >Ainsley
                              > >
                              > >
                              > >
                              > > _____
                              > >
                              > >From: casting@yahoogroups.com <mailto:casting%40yahoogroups.com>
                              >[mailto:casting@yahoogroups.com <mailto:casting%40yahoogroups.com> ] On
                              >Behalf Of
                              > >Rob de Bie
                              > >Sent: Monday, 4 June 2012 5:35 AM
                              > >To: casting@yahoogroups.com <mailto:casting%40yahoogroups.com>
                              > >Subject: Re: [casting] Re: Seeking advice / guidance on parting lines.
                              > >
                              > >
                              > >
                              > >
                              > >
                              > >I use very soft silicone rubber, 10 Shore, and this allows undercuts
                              > >that are almost silly. About the design: these days I always use a
                              > >rectangular block of plastic and thin plastic card to connect the
                              > >block to the master part. After pouring the mold, the rectangular
                              > >block forms the resin cavity. I don't have a photo of this stage, but
                              > >this photo of a mold plus products will also show what I mean:
                              > >
                              > >http://robdebie.home.xs4all.nl/models/images/aqm34-29.jpg
                              > >
                              > >If you want the casting to have a base that's flat on the lower side,
                              > >I would fill the mold's resin cavity completely and then a little
                              > >more, and drop a waxed flat piece (glass, sheet metal, plastic) on it.
                              > >
                              > >Rob
                              > >
                              > >At 20:53 03-06-2012, you wrote:
                              > > >I did have a single attempt at a one piece mould Rob, but ended up
                              > > >with an ellipse rather than a truly circular cylinder :-( I found
                              > > >myself having to slit the one piece mould down about three quarters
                              > > >of its depth to be able to extract the component.
                              > > >
                              > > >As I am planning to eventually use the home made centrifugal caster
                              > > >I have to give optimum results, my preference is ideally for a two
                              > > >piece mould. The castings in your posting look extremely good though.
                              > > >
                              > > >Out of curiosity how do you manage to manage to design your one
                              > > >piece moulds to minimise post casting finishing? Last time I casted
                              > > >a figurine with a one piece latex mould (few years ago), I remember
                              > > >having to invest a large amount of time to get the base flat, post
                              >pouring.
                              > > >
                              > > >Thanks
                              > > >
                              > > >Gem
                              > > >
                              > > >
                              > > >--- In casting@yahoogroups.com <mailto:casting%40yahoogroups.com>
                              ><mailto:casting%40yahoogroups.com> , Rob de
                              > >Bie <robdebie@...> wrote:
                              > > > >
                              > > > > Maybe your project can be cast in a one-piece mold? I do all my parts
                              > > > > this way, and here are some examples:
                              > > > >
                              > > > > http://robdebie.home.xs4all.nl/models/images/aqm34-32.jpg
                              > > > > http://robdebie.home.xs4all.nl/models/images/tbird-12.jpg
                              > > > > http://robdebie.home.xs4all.nl/models/images/e0234-13.jpg
                              > > > >
                              > > > > Rob
                              > > > >
                              > > > > At 14:31 03-06-2012, you wrote:
                              > > > > >Hi. Have just got into making two piece moulds in RTV silicon
                              > > > > >rubber and have discovered parting lines, which isn't something I'd
                              > > > > >particularly considered before.
                              > > > > >
                              > > > > >The project I am currently working on are small cylindrical objects
                              > > > > >about an inch long, which means the parting lines cannot be hidden
                              > > > > >within the design. I was wondering if you guys could give some
                              > > > > >practical guidance on how to minimize parting lines when casting
                              > > > > >items in two part moulds.
                              > > > > >
                              > > > > >On the subject of parting lines, is there a practical way of
                              > > > > >removing parting lines at the post casting stage. The material I am
                              > > > > >working with is Polytek easyflow casting plastic. I'll potentially
                              > > > > >have a couple of hundred or more of these castings, so am looking at
                              > > > > >something not too labour intensive. The onlyother material I work
                              > > > > >in is pewter,so would be appreciative of any guidance on that
                              > > > material too.
                              > > > > >
                              > > > > >Thanks in advance.
                              > > > > >
                              > > > > >Gem
                              > > > > >
                              > > > > >
                              > > > > >
                              > > > > >------------------------------------
                              > > > > >
                              > > > > >Yahoo! Groups Links
                              > > > > >
                              > > > > >
                              > > > > >
                              > > > >
                              > > >
                              > > >
                              > > >
                              > > >
                              > > >------------------------------------
                              > > >
                              > > >Yahoo! Groups Links
                              > > >
                              > > >
                              > > >
                              > >
                              > >
                              > >
                              > >
                              > >
                              > >[Non-text portions of this message have been removed]
                              > >
                              > >
                              > >
                              > >------------------------------------
                              > >
                              > >Yahoo! Groups Links
                              > >
                              > >
                              > >
                              >
                              >
                              >
                              >
                              >
                              >[Non-text portions of this message have been removed]
                              >
                              >
                              >
                              >------------------------------------
                              >
                              >Yahoo! Groups Links
                              >
                              >
                              >
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