Desktop Founding w Low Melt Temp Metal

From Wikipedia:

"A foundry is a factory that produces metal castings. Metals are cast into shapes by melting them into a liquid, pouring the metal in a mold, and removing the mold material or casting after the metal has solidified as it cools. The most common metals processed are aluminium and cast iron. However, other metals, such as bronzebrasssteelmagnesium, and zinc, are also used to produce castings in foundries. In this process, parts of desired shapes and sizes can be formed."

Well... because Makers "don't need no stinkin factories!", we will be using a low-melt-temp metal (58% Bismuth, 42% tin) which liquefies at only 281 deg F. This means you can use a stove or hotplate to get to melting temperature. We'll be using a simple hot-plate. Also, you can use common materials for your mold such as wood, polymer clay or silicone rubber.

This alloy is about 70% of the density of lead so large objects are fairly heavy, but it is non-toxic.   I think it can be suitable for small pendants and key chains and it may be strong enough to be useful for structural parts in light duty mechanisms. 

Bring your own prepared mold, or we will use polymer clay to hand-craft molds, and then cast the tin/bismuth metal into it.  Also, safety glasses will be needed when actually pouring so bring them if you have them. 

Please bring $5 cash to pay for materials (expect about 50-70 g of metal, or 5.7-8 mL), and we'll see you there!

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  • Walt N.

    It was a good meet-up. It is always nice to see and use materials and investigate new processes. Creativity is best when expressed.

    January 13, 2014

  • Craig Z.

    Thanks again to John for hosting and Steve for doing his aluminum demo. As promised, here is some additional info about the stuff we used for the low temp metal work:

    I got the metal from RotoMetals: In one table they call it Roto281F but when you order it they refer to it as "Lead-free, Fishing Tackle Weight Bismuth-Tin Alloy" They have lots of other low temp metals although this seems to have the best combination of affordability, non-toxicity, and melt temperature. If you want to go even lower in temp try out Field's Metal (Roto144F) which melts at 144 F.

    January 12, 2014

    • Craig Z.

      The polymer clay was Super Sculpey (available locally at Jo-Anns or Michael's). I searched for "flexible polymer clay" and found this web site:­ It talks about the properties of different brands of clay and how mixing different types can yield even more flexible end product. I haven't tried anything but the Super Sculpey so I have no additional comments.

      The purple silicon putty stuff is Easy Mold Silicon Putty by Castin' Craft. I bought mine on Amazon but it looks like it may be available at Michael's as well (at least it is on there web site).

      If anyone as any other questions, don't hesitate to ask.

      January 12, 2014

  • SteveT

    I enjoyed this meetup, although I did not get a chance to cast with the low melt metal, being busy with giving my aluminum casting demo. I do think the low melt casting is excellent method for making some patterns that could be then cast in aluminum for higher strength or temperature or less costly application.
    PS: I am sorry I did not converse more with the person who mentioned to me the possible use of a geodesic dome for an observatory - I am excited to discuss that further, so he should contact me.

    January 12, 2014

  • Mike

    That was great! Nothing better than a nice hot cup of metal on such a cold damp day. It was interesting and a lot of fun, thanks to John for having us all over.

    January 11, 2014

  • April A.

    So much fun! We melted and formed small metal objects, saw a demo of aluminum melting and casting, and helped each other with our projects.

    January 11, 2014

  • J

    Excellent! I am always amazed at how much the makers are willing to help with advice, hosting (thanks John!) or to climb into the back of your truck to help you get out of the mud! Thanks, guys!

    January 11, 2014

  • SteveT

    Bring a piece of aluminum if you want to see it melt! (only small pieces please, less than 3" dia.)

    January 11, 2014

  • SteveT

    I am planning to bring my aluminum setup and if it is possible to melt in the first hour, this would give time to cool down to take home. You would probably be able to melt your tin bismuth on the waste heat from my furnace anytime in the first 2hrs. I can plan to demonstrate making two molds from sand which may take just 20 minutes, about the time it takes to melt the my metal. And castings cool within 10 minutes to shake out sand. Looking forward to this meetup. For those not able to make it, you might be interested in seeing me doing the same process about 30 years ago on this you-tube video:

    1 · January 10, 2014

  • Craig Z.

    A reminder for people that I'm anticipating that you'll have about 1/2 a tablespoon of metal to play with. For making a mold in polymer clay, a shallow impression works well (think sealing wax stamp). 3D objects are possible as well as long as they don't have much in the way of undercuts that would make it difficult to remove the original from the clay. For those making molds at the meetup, we'll be making impressions/molds with the polymer clay, then using it to cast metal without baking it. Keep this in mind when deciding what to make a mold of. I may bring an old toaster oven but I've not used it so I don't know how well it will work with the clay. You don't have to have something to make a mold from--you can just free form something by hand.

    January 9, 2014

  • SteveT

    Hey John, I can bring my aluminum foundry and give a demo of doing aluminum casting in green sand molds. I have done the portable thing in the past can bring enough sand to do a couple molds. Does not take much space, just something covered, in case of rain, and ventilated(I use propane to fire my furnace). Let me know and I can plan on bringing it.

    1 · January 3, 2014

    • Craig Z.

      Steve and John, I think this would be a great addition so I hope it can work out.

      January 3, 2014

    • Scott

      To clarify what kind of covered space is needed: at the GEARS show in Portland they set up a kind of open tent, a tarp supported by two 10' or so poles and rope; that worked fine over quite a large propane furnace.

      January 5, 2014

  • Mark B.

    Hi, John. Any tips on parking when we arrive? Will it be obvious?

    January 3, 2014

  • John W.

    An small old Blacksmith shop just begging to get a bit of use:
    If your still searching for a location my place might be a viable option. I have a 5 acre hobby ranch with plenty of room for parking (as long as you don't mind my horses begging for treats:)). My Evil Lair (It's Not A Garage!) is fairly well stocked with woodworking, automotive, and general tools as well as a spanking new (and mostly unused Sherline 2000 CNC milling machine).

    With regard to casting metal, I have an old Blacksmith shop (sadly mostly stripped of blacksmith tools) that might be great for safely casting parts. It was mostly stripped when I bought this place, But I'd love to get a sense of what I might could do to make it a useful foundry/forge (and even happier to share it).

    Probably my Evil Lair would be more than suitable for casting low temp metals. I'd be really happy to have folks over and to share and learn:)

    December 26, 2013

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