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jankers · 09-09-2007

Don,

Thanks for the info.

I don't have a camera but have examined the mould and know where i have gone wrong;- i used large air evacuation tunnels in the two part mould. These where much lager than i have previously used and so the resin did not rise to the surface as i expected, added to which i was experimenting with colouring the resin using Humbrol paint.

The method you use would be of limited benefit to me as the parts i generally cast are 1/128 or 1/192 scale, so hollow casting could prove problematic. If i move to a larger scale then i shall certainly give it a try.

I have now managed to rescue one of the parts so shall just do another mould, it's not really a problem as i use the hot-melt rubber so can just re-use the old stuff. the problem arises due to the very small quantities i normally cast, about 5cc, thus making the mixing a little difficult, the addition of a drop of paint helps considerably in judging if the stuff has been thoroughly mixed as the hardener is only about 3 drops for that quantity of resin. I normally use a syringe to 'fill' the mould, then swing it on the end of a string to mimic the centrifugal machines, it's not perfect but the scrap rate is decreasing.

J.

09-09-2007	#9 (permalink)
jankers Scale Model Member Join Date: Jul 2005 Location: Sunderland Real Name: John My Models: Warships 1890-1920, merchant ships1950-1970 Visit jankers's Gallery Posts: 292	Don, Thanks for the info. I don't have a camera but have examined the mould and know where i have gone wrong;- i used large air evacuation tunnels in the two part mould. These where much lager than i have previously used and so the resin did not rise to the surface as i expected, added to which i was experimenting with colouring the resin using Humbrol paint. The method you use would be of limited benefit to me as the parts i generally cast are 1/128 or 1/192 scale, so hollow casting could prove problematic. If i move to a larger scale then i shall certainly give it a try. I have now managed to rescue one of the parts so shall just do another mould, it's not really a problem as i use the hot-melt rubber so can just re-use the old stuff. the problem arises due to the very small quantities i normally cast, about 5cc, thus making the mixing a little difficult, the addition of a drop of paint helps considerably in judging if the stuff has been thoroughly mixed as the hardener is only about 3 drops for that quantity of resin. I normally use a syringe to 'fill' the mould, then swing it on the end of a string to mimic the centrifugal machines, it's not perfect but the scrap rate is decreasing. J.