While it’s relatively easy to do and get right, to be honest, it’s not as simple as you would think. You have to not only master the ways of Blender but also get the model past the 3D print shop’s automatic evaluation tools.
Measuring the donor ring
Making the ring is relatively simple. If you are making a model of an existing ring, then you need to take precise measurements.
We used a cheap digital vernier caliper that we bought online for about $3 from China. Using this, we measured the outer diameter.
then the inner diameter …
and the thickness … (Note: this one is tricky because the inside is curved, meaning the top and bottom are about 1mm while the middle is about 2mm.)
and finally the height of the ring and made careful notes of the measurements so we could refer to them later.
Making the Ring
Make a circle by pressing “Shift A -> Circle.”
Go to the Scene properties on the properties bar on the right, and choose Metric as your units in your Units panel.
To make the basic profile of the ring, we need to extrude the circle inwards. We do this by pressing “E” for Extrude, then before moving the mouse, pressing “S” to make it scale and extrude. That is to say it will extrude the circle but not in the X, Y or Z axis. Instead it will extrude the points and edges inwards or outwards, as if you were scaling the circle. Push it to about 0.97 which will give you about 1mm proportional to the size of the circle.
Now press “A” to deselect all, then press “A” again to select all. Extrude the ring upwards in the Z axis to about 90cm. (The true height of the original ring was 9mm.)
Now here comes the fun part. You need to make a loop cut on the inner and outer faces of the ring to bulge them out. Press “A” to deselect everything. Now make a loop cut by pressing the button (located on the Mesh Tools panel of the left hand Toolshelf) or by pressing “Control + R.” Locate the outer faces of the ring and wait until the loop cut cursor shows itself in purple in the centre of the faces. Press the left mouse button twice without moving the mouse. This puts the cut bang in the middle.
Repeat the above process with the inner faces. Now select the outside loop cut (in edge mode and with Alt key held down), and scale it outwards by pressing S and moving the mouse. Draw it out to about 1.5 to twice the width of the edge.
Scale the inner loop cut in the same way.
Come out of edit mode by pressing Tab, and go to the Modifiers properties.
Add a subdivision surface to the ring.
Crank the subdivisions up to 3 and 6 for Preview and Final respectively. Rotate the ring and look at it. You will see that the edge of the curve is sharp. That’s not going to be comfortable to wear. The way to fix this is to add loop cuts to sharpen the edges leading to the top and bottom of the ring, and make the edge flat like the original ring.
Go back into edit mode and add a loop cut to the top half of the ring on the inside.
Click the left mouse button, and slide it all the way to the top and click again.
Do the same on the outside. If the bottom edge is sharp, do the same procedure there, too. Now your edges should look more like the original ring.
Now, once you’re happy with the shape, you need to make the geometry you see on the screen real. What we mean by that is that subdivision surfaces effectively cheat; they give the appearance of many smooth polygons where there are actually very few. If you print it now, you will get the basic polygon shape you originally created, not the smooth subdivided shape you see now. We need to apply these computed polygons to the shape as real polygons. This is very simple. Come back out of Edit Mode and with the object selected go to the Modifiers properties. You will see an Apply button. Press it. This adds geometry to make the curves real.
And the polygon count goes up to make it smooth and lovely.
Finally, we want the proportions to be as similar as possible to those we measured on the original ring. In the Dimensions panel on the right hand Toolshelf, change the X and Y dimensions from whatever it is to 2.55m, or whatever size you need, making sure Z is at 90cm.
Note: obviously if the toolshelf is not open, you can slide out the 3D view Toolshelf by clicking the tiny plus symbol on the top right of the 3D view.
Why do we make it in meters? The measured size of the actual ring is 25.5mm, so is that massively too large? Well, in short, to make a ring exactly the right size in the Blender interface would make it too small to see or work with. You can change the scale of the interface, but to keep this short we’ll ignore that for now. And thankfully, we don’t have to, either, because we can rescale the item when we upload it to the 3D printing service. More on that later. The most important thing is that the ring is in proportion.
Prepping for Print
Once the model is to your liking, then you can prep it for print. If you are lucky, you only have to do this one step. Go into edit mode on the ring one last time. Got to the bottom of the Toolshelf on the left, and you will see a button marked Remove Doubles.
This will delete any vertices which occupy the same space which happens during the course of making a model. Doubled up vertices create havoc in a 3D printer and add a little size to the object too.
Note: if the model is complicated, then you may have to thicken any really narrow areas to make them printable, but more about that later. The last step is to save the object for printing, and a wise choice is STL, but you can also use DAE if you wish.
Uploading and Checking (Shapeways)
For this example, we used the popular Shapeways online 3D print service, as it’s popular, accessible worldwide and fairly inexpensive.
The first part is very easy; you just upload the STL file you exported in the last step.
Then the trouble begins. Because you didn’t set the object to be a specific scale size in Blender, you have to wait until it loads and see what size it is.
In this case, it was almost 7cm wide instead of 2.59cm, but you can rescale it in the interface of the web site. Once the object is loaded and processed (which may take some time), look for the SCALE button and press it. Here you can resize the object to the correct scale.
Once you’ve done that you should look at the various materials down the page and see if it’s passed all the tests.
There are physical limitations on how thin something can be and still be printable, and this varies between materials. For example, objects which are destined for printing in metal need to be a touch thicker than those designed for plastic. If there are any problems with the thickness of your piece there is the option to automatically fix it, and this plumps up the mesh of your object in the problem areas. It’s by no means ideal, but it worked well sometimes and can save you a lot of time reworking your model and uploading it again. Obviously you should order a cheap plastic print to check the print for size and then make any adjustments you have to make before ordering a metal ring in Rhodium plate, silver or even gold because that’s a potentially expensive mistake.
Conclusion
Making jewellery in Blender and 3D printing is a very rewarding, if a little time-consuming, pastime. If you have any questions about 3D printing or Blender, please don’t hesitate to ask us below in the comments.
