A pendant design based on the sigil of the Clayr from Garth Nix's Abhorsen series. This model can be printed directly or, more interestingly, cast in metal using provided molds.
The default size is about an inch and a half across and weighs less than 2 ounces when cast. Almost all parameters are adjustable via the Customizer.
I've provided files to print a whole pendant, a half pendant, and a mold (for casting in the material of your choice).
For full directions (with more pictures) see the writeup on my website.
Printing a whole pendant
To print a whole pendant in one go, use the Pendant.stl file provided. You'll DEFINITELY need support with it.
Printing a half-pendant
To print a half-pendant, print two copies of the PendantHalf.stl file provided. It shouldn't require any support material. Glue or epoxy them together.
Casting a pendant
This project is the pilot for a generalized metalcasting method using 3D printed molds. In order to be able to cast directly into a mold, we need to use a special metal, see below.
Although I've provided a number of different shapes, I recommend using the projection-shaped molds throughout.
The metal we're going to use is a Bismuth-Tin alloy, and is non-toxic. It's not food safe, so don't try to eat it. The particular alloy (which I bought on Amazon) melts at 138C/281F, which should be readily achievable on a stove-top. I elected not to use the oven in case of contamination by fumes - as I mentioned earlier this is NOT food safe.
- 3D printer & plastic
- Metal of choice (though I very much encourage you to use the one I recommend)
- 2+ Clamps
- A container to melt metal in (chemistry lab quality glass preferred). This container will end up holding the leftover metal after it solidifies - you probably will not be able to use it for anything else.
- A container to catch melted metal in (again, chemistry lab quality glass preferred)
- Print the molds. I'm currently using 0.05mm layers, 0.8mm thickness for all dimensions and 8% infill. These settings may need adjustment for your printer - but should provide a good starting point.
- Clamp the molds together as shown in the third gallery picture.
- Cool all the molds in the freezer for at minimum 3 hours.
- Melt the metal. THIS STEP CAN BE DANGEROUS. Always wear safety gear - at a minimum eye protection and gloves that can handle the temperatures. (Oven mitts work wonderfully).
Any way you can heat it works. Ideally, use a chemistry lab quality glass beaker and a hotplate. If you don't have access to these, I suggest a flat-bottomed Pyrex bowl on the stove, although I've seen it work with ceramics and glass. Stay away from the stove while the metal is heating, in case the container has a flaw that causes a catastrophic failure. If you have an extractor fan of any kind, use it. Finally, DO NOT quench or dip in water the container of metal. Let it cool in its own time.
- Set up the area around the mold. Raise the mold and clamps up above a container that can catch any spilled metal. Again, use glass or ceramic containers.
- Pour the melted metal. Pour metal slowly into the funnel until the funnel is about half full and stays there.
7.Agitate. The mold needs slight agitation as the metal cools. This agitation helps remove any residual air so the metal can fill the entire mold. I found that picking up the molds by the clamps and giving them small shakes for about 30 seconds worked extremely well.
- Wait. Wait until the metal in the funnel is solid and warm to the touch (rather than hot).
- Remove the funnel from the other mold parts. Start by removing the clamps. The funnel will be stuck to the two smaller pieces of the mold by a small cylinder of metal. In my experience, twisting the funnel will remove it.
- Freeze for 3+ hours. This will cause the metal to shrink (and it shrinks more than the plastic) which will make the final part easier to remove.
- Remove the part from the mold.
11a. Method 1: The first half is easy to get off - you ought to be able to, with some difficulty, pry half of the mold off. The other half is more complicated. Put your thumbs in the center of the backside, grab the edges with your fingers, and bow the mold as if you were trying to push the metal out from the back. Repeat several dozen times, rotating the mold between attempts. Very quickly you should see all the points and all the keys come loose, so you can bend the mold and they don't bend. Further bends are to loosen the center, which eventually pops out. If needed, freeze the mold again. Make sure the part has somewhere soft to land - I broke several by popping them out onto a hardwood floor.
11b. Method 2: Cut the metal free. If you don't care about reusing molds, this may be easier. The methodology for cutting the mold is up to you. But be mindful of exposing the metal to heat, if you choose to use a heat-based method.
- Cut off the nub on the back. Removing the pendant from the mold leaves a metal nub on the back of the pendant. I used a Dremel cutting disk to grind it off, though many methods will work.
- Hang. Hanging the pendant is another place where you get to choose the methodology. My favored method is to use jeweler's wire by cutting a length, folding it in half and running it through the small hole in the top-most point. Then I bend the two ends back around to the side that now has the loop and solder them together. This way it can be hung on either a continuous chain or a chain with a clasp.
- Celebrate. You now have a custom pendant! The .scad file should be adaptable to many different shapes. Play around, but expect some difficulty - OpenSCAD doesn't let you query some properties, meaning that you'll have to adjust them manually.
- It has been my experience that the molds do not melt overmuch, and could possibly be reused for multiple castings. However, i haven't tried doing so, mostly because I needed to make design revisions from mold to mold.
- I also looked at Field's metal, which melts about 62C. Field's metal is a well-known non-toxic alloy, and the one I came across most in my search. However, the cost for this is exorbitant - $100 for 4 ounces. I decided to go with the cheaper but harder to melt metal for pure cost.
- Any mistakes or the metal left in the funnel can be remelted with the remaining metal in the container for use in other castings. However, do make sure that no plastic makes it into the metal to melt.