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Platinum casting % shrinkage

I need to make an ornament ring, it is flat , I need to have it finished 70.00mm outside diameter , the ring is flat and it is 3.5 mm thick, it us platinum, can someone advise what size should I make in CAD ; does it shrink more than silver or gold ?
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I have never worked in platinum, but why can’t you fabricate it or just cut it out of flat stock?

Thank you for your comment
I can not cut, because there is a lot of detail and diamonds going on it .
It would be possible , but making a CAD will be better and much easier

hi,

if you are sending out for printing, you could call , send the file, and discuss with them. I would also discuss what printers are available, and how the item can be printed to get the smoothest print, for less metal loss from finishing.

i would avoid assuming anything…certain machines are better for certain things…cleaner surfaces…flat surfaces, etc…i would guess resins are different too(?)

just my thoughts

julie

Thank you so much for your comment.
I am using an envision printer, i get a smooth surface .
There is very little difference from the CAD to the printed piece , but there is a shrinkage at casting and the polishing , which I was calculating around 7% , but not sure if that is right, because I have never made a puce this big in platinum .
Thank you
Jorge

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What does your caster think about casting envisiontec resin in platinum? Check with them to see if they can cast direct or plan to make a mold of the resin print, then cast from the mold. The answer will determine what shrinkage you should allow for. When casting direct from a wax print, such as a projet printer yields, I will usually scale up 1%-3%, depending on cross section thicknesses - Steven

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Thank you for your comment.
I am using easy cast resin, I have casted in platinum , but there is more porosity than wax .
But I will try again ; and gating has a lot to do with it too.
You mentioned 1 to 3% shrinkage; I thought the complete process from CAD to silver model, to tubber mould , wax injection and cast is around 6%.
And , I am not sure but I think platinum shrinks more than silver at casting.

Sorry it’s taken so long for me to get back to the forum. So…
If I am printing in a resin other than pure wax, I find it better to make an RTV mold of the print, then use those waxes to cast platinum. Typical platinum investment/burnout does not like resin, although if you use dental investment you would stand a better chance.
Shrinkage - I was thinking of just casting the print. If you then plan to make a mold of the cast part, what kind of mold? Vulcanized rubber or non shrink RTV? That will determine overall scaling up to compensate for shrinkage and finishing. And getting back to my comments above, if you are planning to make a mold anyway, you should cast the original in silver to avoid the resin casting problems with platinum. - Steven

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