Multi-Part Mould Making Assistance!

Discussion in 'Replica Props' started by MarkHeyster, Aug 31, 2015.

  1. MarkHeyster

    MarkHeyster New Member

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    Good morning!

    I was hoping to gather some input from somebody who knows a thing or two about silicon mould making, as I'm afraid that I've become a bit stuck! This is my first multi-part, large-ish moulding job and I'm struggling to wrap my head around it.

    I need to produce a silicon mould for the model below in order to produce several copies, however in order to have a separate 'magazine' to fit back into the body of the weapon, it is necessary to keep the large hole open on the underside of the body.


    Due to the relatively symmetrical nature of this model, I was hoping to use a 2 part mould using the line of draw shown in the picture below (apologies for the really rough lines!) to reduce mould complexity, however the cavity is at 90 degrees to the line of draw and I'm worried about an undercut.


    My question is: if I cast it using a 2 part mould as I've shown, will the flexibility of the silicon mould be enough to flex out of the cavity once opened, and allow the piece to release from the mould? And if not, does anybody have any suggestions as to what might be a better method use in this instance?

    I plan on using a 21 shore condensation cure silicon, which I've been told is quite flexible.

    Any help would be most appreciated!

    Thanks ever so much,

    Mark Heyster
  2. robn1

    robn1 Master Member

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    It depends how you plan to cast it. If you're rotocasting to make a hollow piece, you can fill the cavity with clay and cut it open on the castings.

    If you intend to make solid castings I'd make a 3 part mold, with the third part being an insert for the cavity.
    Sean likes this.

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