A lot of my work involves creating fine detailed basket and cage structures out of metal. Usually 20 ga square wire or smaller. I am making rubber molds of these structures with the intention of casting them, many at a time.
How can I make sure these castings go smoothly, with all of the spaces being filled up? I know molten metal sometimes has a hard time flowing through delicate structures, but I also know it is possible. If anyone has some experience to draw from and advice to give me before I start the trial and error process, I would love to have it.
I am using a vacuum casting setup, with an electro-melt. I will be doing this in sterling silver at first. Should I pour at a higher temperature? Should I do something special with the burnout cycle? etc…
The cages you will be casting are probably similar to filigree which is a difficult process but possible. You will have to experiment and find out what works for you. The design may have to ba altered to facilitate not freezing off too quick. E.g. Larger gauge wire, higher temperature throw, hotter flask, etc. you might have to have some failures to see what your options are. A casting consultant might be able to save you time by viewing your pieces and making suggestions.
Cheers
Sam
Thank you for this info! I will do some test castings and go from there, but it is good to know that a higher temperature throw or a hotter flask may help. If I discover anything significant I will post it on here.
Where are you located? Have you already successfully created the rubber mold and shot waxes? If so they should cast fine. I’d experiment with increasing the flask temp maybe 50 degrees hotter and see if it fills. If not another 50 degrees. If not still then maybe try the pour temp 50 degrees hotter. My fear would be if the pour is too hot the metal will be brittle. You may need a professional casting house as they will be pushing the metal under pressure and pulling it under vacuum all at once. When I think my castings are good and then have someone with do some for me with a 50k machine as opposed to my 2k setup, I’m amazed! Even how close they can clip the sprue without touching the piece.
I have some lattice and wire type molds and cannot shoot a good wax. I’ve had success with the Yasui wax injector that vacuums the mold first than shoots the wax in under pressure. Removing the delicate wax from the rubber mold is another story! On 3D pieces my fingers get in the way! Send some pics as there are many lifetimes of experience on board.
Hi @CharlieB. I am currently located in Albuquerque New Mexico. I actually posted this in order to get some preliminary information before I start making all the mistakes. I am making my rubber molds now and I will keep this forum updated with my progress. I’ll try that tip of making the flask a little hotter too.
Hi Jack,
Since you are in Albuquerque, stop by Rio and consult with the Tech support team. We are always available to assist with casting issues and have a lot of resources to help guide you through the process. We would be happy to offer any type of assistance we can to help you be successful in your venture.
Phillip Scott
Technical Support Department
Rio Grande
One thing that i might suggest is adding small sprues that extend a bit beyond your fine cage element - maybe even a sees of small balls or similar that serve as mini reservoirs. If your metal is the correct temp with some sprues of marginal thickness… there might be add some pull to the remote / extreme ends away from the button. If you are losing the existing metal it could be to some shrinkage. I tried it in attempt to fool the cast piece into thinking is further out there than it really is. It might eliminate some of your problem.
I cast some hand constructed wax pieces that had flow issues. It worked by directing the metal beyond the piece. I trimmed afterwards and had a casting without porosity and shrinkage issues.
Eileen
pscott
March 30 |
Hi Jack,
Since you are in Albuquerque, stop by Rio and consult with the Tech support team. We are always available to assist with casting issues and have a lot of resources to help guide you through the process. We would be happy to offer any type of assistance we can to help you be successful in your venture.
Phillip Scott
Technical Support Department
Rio Grande
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Eileen has a good tip there. A little extra wax wire at the ends of a run definitely helps with long, skinny pieces.
I think the most dramatic help for you would be to cast the pieces using centrifugal. I would crank up the flask temperature pretty high too, say 1050 for silver and 1150 for yellow gold. Same thing with the metal temps. You really don’t have to worry about porosity so much with those thin pieces like you would with heavier structures so you can be a little heavy handed with the heat.