Mould sprue alterations

[johncast]

Hi

I have a large number of wax silicone injection moulds that I would like to alter slightly. The sprue shape is not quite to my liking and would like to make a alteration to these moulds with some silicone material to change the shape of these sprues channels. The moulds are made of Dow Corning green rubber 4130 J and there are over a 130 sprue channels to alter.

Does anyone have a suggestion as to what silicone material would be good for such a job. There is only a slight heat resistances needed here as the silicone will only be in contact with wax of 80oC .
Thanks
Johncast

[mangozac]

Just to make sure we understand your requirements do you actually want to fill in a lot of the existing sprue channels?

Why not use the same rubber that the moulds are made of?

[johncast]

Hi Zac

The sprue in the moulds is a T shape but the connection of the sprue going across to the down section is webbed. I would like to remove the web and have a sprue that is a neater sharper T. I had thought of using the same rubber as it sticks to itself very well but to set up some system to be able to pour 30 or more moulds at a time and not have the rubber flow down into the cavity of the parts is quite time consuming. I expected that some tube silicone would be a quicker alternative.

Johncast

[mangozac]

Ahh I see.

What about adding some thixotropic compound to the silicone to make it more gel-like? Something like (although that's only for condensation cure silicone)...