It’s really not hard to make a custom / cool / funky ring in 123D, let me show you how!
I'll be working in millimeters, which is the units I recommend when making small jewelry. So if you have a metric ruler I highly recommend having it by you when modeling something small.
Before I even start I'm going to decide which material I'm going to make this in. This is important because I don't want to make something too thin and fragile for the material I decide on. My usual favorite is Durable Plastic (which is easily dyed using fabric dye and sealed using non-toxic sealer). But since I've never personally tried jewelry in Superfine Plastic White that's what I'll go for today. As per the material page (http://www.ponoko.com/make-and-sell/show-material/381-3d-printed-superfine-plastic-white) the minimum wall thickness on this material is 1mm/0.04" and the mimimum detail is 0.2mm / 0.008".
Open up 123D. Go to the very upper-left corner and click on the drop down menu. Go to Options>Controls Make sure "Snap Bar" and "Sketch Grid" are checked. Press OK
The Interior Circle of the Ring
Go to the Viewing Cube in the upper right corner and click "Front." From this front view it will be easiest to start our basic shapes.
One of the most common ring sizes is 7US, which is 17.5mm diameter, so that's the size I'm going to use as an example. To find your own ring size diameter here's a handy chart on Wikipedia: http://en.wikipedia.org/wiki/Ring_size
Next go to the Toolbar and click on Sketch>Circle
Click on the point where you'd like the center to be, then specify the radius of the circle. In my case the diameter of the ring size I want is about 17.5mm, so I'm going to input 8.75mm as my radius.
This circle defines the interior shape of my ring.
The Basic Outer Shape of the Ring
Now I'm going to Offset the circle by clicking Sketch>Offset on the toolbar. Then click on the circle you want to Offset, this will define the outer thickness of the ring. 2mm is what I'm going to offset it by, not just the 1mm minimum thickness. This is mainly because this (Superfine Plastic) is a medium durability material and I want the thickness to compensate.
(Optional) If you want the top of the ring to be a little more interesting now is a good time to draw another shape on top of the existing ones. Go to Sketch>Spline and draw your curve/spline by clicking each point your curve will go through, make sure the shape is flush to or intersects the ring shape. The precise input area is less important here, but you can certainly experiment with it! Press Enter or right-click OK while on the last point of your line.
Bring Your Shape into the Third Dimension
Before this next step go to the Viewing Cube in the upper right corner and click on the little house icon. This will put the drawing you've made into perspective view.
Back up to the toolbar click Create>Extrude and make sure to hold Shift down in order to select all areas you want to bring into the third dimension. The precise input box will pop up yet again.
You could use the arrows to visually extend the piece, but I'm going to be exact and extrude it 4mm by inputting it in the box. Remember if your materials wall thickness minimum requirement is 1mm make sure to extrude it at least that much, at least 1.5-2mm is recommended for thin unsupported areas like the bottom of the ring (plus most thin-style rings are about 3-4mm wide).
It is currently printable as-is.
What's in Part 2?
I do first recommend taking a look at Part 2 if you want to add more dimension to your design with slightly rounded edges (Fillet tool) or to add a whole new flat area in place of the edge (Chamfer tool).
I’m also going to have an additional step at the end where we’re going to add a whole new shape that will be the top of the ring.
*This is a very good time to save your 123D file if you haven’t already. Just go to the upper left corner dropdown and Save. In case I don’t like my final result and want to go back to a previous iteration II generally save different versions of each project as I go along.
Export to Print
So if you like it now then go ahead and export it to an STL file and you can upload it to your Ponoko account.
*Do note that due to upgrades and integration with Autodesk's website you now need to be logged in to export to STL. It's a free account and you can download some free editable files from the site once you have one as well as share your awesomeness with the 123D community. Some programs charge to allow STL export, so it’s not a bad deal just to put in a bit of info. You can sign up from within the 123D program by clicking on the word Gallery in the very upper right-hand corner of the program.