"Casting large items- HELP please" Topic

Hi. We are having problems casting larger items in our centrifugal casting machine. 28mm figs are fine but anything bigger goes all 'bitty' and horible. The metal goes all mottley and holes appear all in the casts?
Any help resloving this problem as we need to get casting our 28mm elephants again. If you need any more info or even pictures i can post some for you.

I had this problem with a larger figure and eventually realized that I simply wasn't spinning the mould for long enough.

Leave it to spin for a couple of minutes and see what result you get then

Mike

Yes we would say spin the mould for longer as well, also with large pieces the mould gets very hot very quickly so you might need to spin it just once and then give it a rest to allow cooling before spinning again. If that doesn't work then let us know and we will have another think. Jo:)

Humidity is also a factor and is contributing to the "pitting". Spin it longer, and allow the mold to cool before recasting it.
Good luck,
R.

If the quantity you need is relatively small (say 20 or so per week) then fill in any pitting with milliput if the remainder of the surface is good.

Yes, spin it for 5 mins if possible. Consider re sculpting the elephant in to two halves or use bismuth based alloy (expands upon cooling)

Martin

See you at the Cornwall show on the 25th August.

We had this problem constantly when I was working with SHQ mouldmaking and casting. the problem is caused by elementary physics! metal expands when hot and contracts when cold, that shrinkage has to go somewhere. More dusting in the moulds and longer spin time may help but the problem will always be there.

The only way it could be resolved was to use a higher bismuth alloy, which is one of the only metals that expands upon cooling as martin says. Or better still consider having the elephant re-worked, I'd love to have a go, and it may not be as expensive as you think.