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A couple fun facts about casting metals: Many of them shrink when they solidify. For the size and tolerances needed for a ring you can probably ignore this det
by mauvehaus 2y ago
A couple fun facts about casting metals:
Many of them shrink when they solidify. For the size and tolerances needed for a ring you can probably ignore this detail. You can get what is called a low-shrink mold made for some alloys that helps mitigate this if you want to make your prototype to finished size (or you didn't know better before you takes to the jeweler).
Patternmakers deal with this using what are called shrink rules. They look like regular rules, but are e.g. 5% longer. If you're buying an old rule, make sure you don't get one by mistake.
Silver rings, worn regularly, won't need to be polished to keep the tarnish at bay; the contact from your skin will do quite well enough. Our wedding rings are also silver, and I've only polished mine when I haven't worn it for a while. Ours probably don't polish up to quite the same luster though. They're a regular alloy of silver for jewelry and not silver and gold.
- ggreer 2y agoI was worried about the metal shrinking, but I only had to increase the size of my prints by 1.6% to get the desired ring size. eg: The PLA ring had an inner diameter of 16.8mm and the casting had a diameter of 16.5mm. Thanks for the info about the lack of tarnish. I'm glad I won't have to do much maintenance.
- mauvehaus 2y agoSince you cast this a few times, I have to ask: did you determine the shrink ratio empirically or were you able to look it up? This is a super cool project, and I'm impressed that you got it done before the wedding!
- ggreer 2y agoI looked around online and answers ranged from no shrinkage to 6%. For my first attempt I split the difference (3%), then measured the actual diameter with calipers. Also I tended to err on the side of making the ring too small, as it’s pretty easy to remove material from the inside of the ring.
- Lev1a 2y agoEven if you have tarnished silver things, like silver(-plated) cutlery etc. the "un-tarnishing" is stupid easy and cheap to do: - take some container and put warm/hot water and a large helping of (table) salt into it - put some scrunched up Al foil into the water - submerge the objects to be untarnished in the water so that the silver touches the Al foil - leave for a while in a well ventilated area (since it will smell of rotten eggs) - rinse well - done. recipe from a kid's chemistry set I had a looooong while ago, used it successfully quite a few times on my parents' silver-plated cutlery they've had and used regularly since their wedding decades ago.
- interludead 2y agoYet this shrinkage is typically minimal