This Instructable shows you how to obtain a 3D scan and turn it into a custom silver necklace.
I started this project because I wanted to make a necklace of Hoa Hakananai'a, a large Moai statue from Easter Island, that is housed in the British Museum in London. Using some basic 3D modelling tools, a bit of outsourcing, and a little elbow grease, we'll be able to produce our own monumental jewellery.
Step 1: Get a 3D Model
Many museums including the British Museum and the Metropolitan Museum of Art are digitally scanning their collections. Some of these models are freely available online. I was able to find a model of Hoa Hakananai'a here:
If you search around on various websites you can get some really great free digital models. At the end of this page I've attached a few links which are a great reference for finding 3D Models.
Another method of obtaining a 3D scan is by using an app like 1-2-3D Catch. This requires you to take photos from many different angles and then the app patches them together into a 3D file. The process is really simple and with some practice you can get a really good quality 3D capture.
Step 2: Preparing the 3D Model for Printing
Now that you've found a 3D model of what you would like to cast, you will need to prepare the file to be sent off for 3D Printing in wax. The file that you have downloaded has likely come as one of the following: .OBJ, .IGES, or .STL. You will need something to open this file in. While there are many types of software available for both Mac, PC, and Linux, the images above are shown modelled in Rhino.
Rhino for Macis currently in Beta mode and is freely available for download.
Blender for PC and Linux is also a good and free option.
Once you have the 3D model open, you will need to examine it to make sure it is lean and ready for 3D printing. This is a necessary step as sometimes these files can contain small artefacts that should not be printed. To clean up the model, simply look for any out-of-place bits and delete them. You will also need to scale the model at this point. I chose to make my piece 30mm tall (~ 1 - 1/4").
Next, you'll need to decide if the ring that connects the object to the necklace will be built into the 3D model or if you will solder a ring on later. I chose to solder a ring on at the end.
The image above shows a ring being attached onto the model.
Step 3: 3D Printing in Wax
Before the model can be poured in silver, it will need to be printed in wax. This is because the molten metal will be poured through a method known as "lost wax casting".
Once the object has been printed in wax it can then be sent off to be cast in silver.
3D Wax Printing is quite affordable and many local 3D printing & fabrication companies will offer this service. However, here are a few suggestions that are national:
In the USA: http://digits2widgets.com/3DWax.html
In the UK: http://www.precision-wax.com/
Step 4: Casting the Metal
You may be able to find a service that both prints the wax positive and casts the metal for you, however if you can't your next step is to find a casting service. The casting technicians will attach your model to a sprue and pour investment plaster around it. After this the wax will be burned out from the plaster mould and the molten metal will be poured in.
Depending on the casting service you can choose from many different kinds of metal. I chose sterling silver as it polishes nicely, feels weighty and because currently silver is not very expensive. My piece was less that £8.00($12) in material cost.
Here are two US & UK Sources for casting, however, your best bet is to contact a local jeweller's shop and ask them to recommend a casting service.
The image above shows multiple wax casts on a large wax sprue.
The other image above shows the wax print next to the final silver cast. Note that there is a very small amount of shrinkage that occurs when pouring the silver (around 5-10%).
Step 5: Cleaning Up the Silver Cast
You now have a silver pendant. Depending on what service you paid for your pendant may need a little extra work. If it is still on the sprue (the metal stick) this will need to be sawn off, with a hack-saw, and filed down to remove the stump.
During the casting process the silver will have become oxidised on the surface. To remove this you must put the piece in a pickling solution. There are many ways of doing this but a simple solution of warm vinegar and salt works fine. Just clean up the silver under running water using a toothbrush and then drop it in the warm acidic solution for 30mins-1hour. When it comes out it will look brighter but still not shiny.
Step 6: Soldering (If Required)
At this stage you can solder the jump ring on if you didn't add this to the original 3D model. I bought solid sterling silver jump rings and cut one and bent it to make it fit better. The way you choose to connect it totally depends on your model and you may even prefer to simply drill a hole.
I wont go into detail on how to silver solder as there are thousands of videos online that instruct you on this process but I have taken an image of how I set it up. I used a kitchen blow torch for the soldering and silver solder flux paste. After this it is back into the pickle solution for a while to clean it up and then onto the polishing.
Step 7: Polishing
There are many ways of polishing silver and much information about this online so I have attached a few links below. However different kinds of polishing give different effects. I was lucky enough to have access to a magnetic polishing machine but you could use a tumbler, a wheel polisher, aluminium foil and baking soda, a fine pumice powder or I'm sure you could create some kind of felt head for a drill bit and polish it that way too!
Step 8: Put It on a Chain
The last step is to simply attach the chain and now it is done!