Technical Memorandum of My 3D Printed Engagement Ring — Project Panic Moon

So, I realized that I had found the one.

This is a recollection of details and knowledge that I decided I had to gain the day I decided that asking to get married to the person I love was going to be my weekend project for a few months. After having been through this process and having talked to friends and work colleagues, I realized that there was a lot of technical information involved in doing what I did, and perhaps someone out there might benefit from some of this, and perhaps “take the next step” by adding their own technical expertise to this little science project.

So, I decided that I needed a ring.

For whatever personal reasons I had when I made the decision, the day that I decided that I was going to propose, I realized that I had to start figuring out how to get a ring. It is the tradition, after all.

I’m an engineer at NASA. I can deal with communication protocols between various vehicle components designed by multiple companies with different specifications. Yet, the more I looked and asked about these social protocols, the less practical sense they seemed to make. Okay, so I needed a ring. “What is the typical ring that people get?” I’d ask parents, and friends, the internet. Well, it seems that it varies. I had talked about it briefly with my girlfriend, but she wanted to be surprised. I had to work in secret on what seemed each day like a project with escalating complexity. My own personal skunkworks project. It may be the first time I had to build a product where I had to keep the details a secret to the end customer.

So, I tried to buy a ring.

The market for engagement rings is a wild conglomeration of choices. There are different settings, sizes (“what’s her ring size?” *panicked realization*), metals, designs, prices. I quickly realized that the most difficult problem was going to be price. I learned that there’s a social cost for the price for her, and personal budget cost for us. After all, do we want to wear a car on our hands? Why? Seriously, why? What will her friends think of her choices in me judged by my choices of an ornamental object? Ball’s in my court for this.

It seems that the internet is a big help when it comes to getting specific answer to any question, but terrible at helping when we want any answer to a specific question. You get answers, but you might not like most of them. How much should the ring cost? 3-months salary?!?! Of course, this is just one opinion, probably originated from the companies that make these rings. I understand; I’m not going to judge marketing effectiveness and corporate manipulation. I had to get above it somehow. 3-months salary? Is that before or after taxes? After all, if an object is suddenly fixed at percent of earnings, then it might as well get thrown into the tax calculations. I digress.

So, I decided to build the ring.

I’m an engineer! If I can design a spacecraft, a computer, or a UAV, I can certainly put together a metallic object with some minerals. I needed equipment, but I was only going to build this once. Well, if it goes well, I might be able to use the same methods for doing future projects. At least that’s what I told myself. Bracelets? Necklaces? Earrings?

I sat down and did a cost-benefit analysis of my options. If I built the ring, then it would take longer. I would also need to maintain it myself. I would need to figure out how to purchase the components, as well as design the mounts. Those gems have to get on the ring somehow, right?

If I bought the ring, then I would admit to having paid for the cost of the vendor to store and house all the other rings, as well as the production and design costs. At the end of the day, I was also picking something that someone else has designed, possibly in large bulk design quantities. There’s something to be said about selecting a design, but it isn’t as customized as having designed it myself. I could also get a hand designed ring from an artist.

Design my own ring. Save on cost, and ensure my own design really says who I am. Easy decision here. I’m building my own. Let’s dive into the details.

A ring is composed of 2 or more components.

In spacecraft terms, a ring is simply a radial mount, or coupling component, for attaching an optical quality mineral to a human finger. Before we go on, I should warn you that even though I may sound curt with some of these descriptions, it’s just the way I look at an engineering problem. I actually quite enjoyed the process throughout this project, but poking at the problem with humor allows me to diffuse the difficulty of the problem. Sizing an opponent is likely a coping mechanism to uncontrolled risks.

The first and most important reason for the ring is the object attached to the ring. Yes, I know that the person is the more important feature, but let’s stay in engineering world and design around the requirements. The object is an optically cut piece of mineral. The optical properties are optimized for reflecting light in a very particular way.

Light comes in through the various faces, strikes the opposing facets, and get reflected out in very constrained directions in unison to create the illusion of “sparkle” and “fire.” This is the basic manifestation of cut. Of course, the attenuation of the light due to particulates and other impurities in the crystal will change the light a bit. This mainly manifests as color.

The radial size of the gem defines the size of the surrounding mounts as well as the amount of scratching and social feedback (social scratching) it creates. This is manifested as carat.

The last one is one that most people care too much about but don’t quite understand, which is clarity. My analysis shows that with enough sparkles, there’s a grade value (VS1?) where most humans will not be able to tell without instruments. Nobody showing off a ring is going to to bring an instrument to judge their friend’s ring. The only purpose this metric serves in the long run is resale value; however, I have no plans for that alternative. There is actually a real engineering value for this metric, and it has to do with the mounting process, which I will describe later. In short, flaws in the crystal become sites for propagations of force failures. These imperfections are where cracks propagate from and lead to cracks and chips in the gem.

After a rather long iterative process of shopping for various suppliers, I decided on these specifications, in this order of importance.

C1-Cut: Must be optically near perfect (Very Good -> Ideal)

C2-Color: Must be indiscernible to the average person on an average day’s lighting and most indoor lighting (J -> D)

C3-Clarity: Must be at least store grade for presentation (VS1 -> VS1 — I really don’t need any better)

C4-Carat: Must fit our budget (honestly, I’d be surprised if you can tell the radial difference between 0.6 carat and 1 carat — you’d have the eyes of a caliper)

I essentially optimized for presentation, because that is the primary long-term mission of this ring. The ring doesn’t provide love, I do! The ring provides advertising?

There’s also a few other aspects about gemstones that are of note, which is origin (C5-Culture).

The final selection was a super ideal, G color, VS1, [Carat value classified under the marriage partner skunkworks act of 2015] ## carat stone from http://www.brilliantearth.com/. This means that my diamond was going to have no bad history (fewest deaths per diamond), and be totally human-made. Perfect! This ring is going to symbolize, in part, my personal respect for humankind’s technological capabilities and achievements in bettering the human condition. Put this under “Vote with my wallet.” This thing was also going to sparkle like a disco ball and be white as I can get to a 5800+ Kelvin star. Within budget, of course.

I’d like to briefly dive into a historical tidbit about artificial diamonds.

According to Wikipedia (to save you the trip), a synthetic diamond is created by applying pressure to a sample in a specialized conductive container. Pressure is applied then very high electrical energy is used to atomize by vapor or direct application to the carbon atoms in the sample; and voila, a diamond crystal is born. You know that dirty carbon deposits on the spark plugs in your car? It’s similar.

This process could theoretically be mass produced, but there are probably shadowy economies at work keeping all of this in balance. Needless to say, I also considered cutting all my hair and having that turned into a diamond. Kinda creepy, but probably not as creepy as the idea of turning corpses to diamond. Really, look it up, it’s interesting reading.

At 9.5~9.7 hardness, there’s another crystal called moissanite that I also considered. At 1/10th the cost of a diamond for equivalent sparkle, nearly the same hardness, and equivalent size. Let’s just say that this was a really difficult engineering decision to pass up. It was also inspired by meteorites! However, after a very long and difficult couple of days of thought, I determined what I wanted to say in the long-term social mission of this ring, and I decided that the central stone was going to be a diamond, but I was going to have moissanite on this ring, to make a point. Sometimes, we do things to say “Damn it, I understand it but I’m going to still prove a point.”

The inventory thus far includes, 1 radial coupler, 1 diamond, moissanite, and some smaller gems that do something cool.

Still, while reading about moissanite, the idea of asteroids got my attention. There are gems that come from space? Who knew! Well, I kinda knew of it through prior reading, but it hadn’t occurred to me to jewel it. So I did some research. There’s a class of crystals called pallasites (https://en.wikipedia.org/wiki/Pallasite). Pallasites are crystals that actually form in space. When asteroids whizz about the solar system, they collide from time-to-time. These kinetic impacts generate massive amounts of heat that cool very quickly in the coldness of space. The crystals that form are often small peridot crystals that take on the composition of the chemicals in the asteroid.

nasa.gov

Pallasite Formation (http://www.sciencemag.org/)

I guess knowing this, I had to ask where I’d find a place to get me some jeweled pallasites. This is the jewel-quality pallasite gems. Actual image of the stone I ended up using as decoration stones.

I guess this ring is now a space worthy ring, with real samples that came from space. I’ll have to call this the Ring of the Sol (haha, get it?).

So, I designed the ring.

Decision time. Do I design my own ring? I’d like to, but that means having to deal with issues which I had no real expertise at. So I had to quickly do a trade-off study between learning those skills and the risks associated with the ring. If I wanted someone else to design the ring, I’d still have to figure out how to find that person. Not as big of a problem. Some people do this. Freelance designers post their work on forums, and will provide services for this. Someone else who designed their own ring gave me a lot of inspiration for doing my own, and on his site, he lists a few designers.

Recommended Reading: (http://christian.gen.co/ring).

For me, I decided that I was going to do my own ring. I knew that I’d be doing it in Solidworks because that’s the program I had the most training and familiarity with. I could learn to do all of this on Blender or something but that means extra learning time and extra issues that I didn’t want to have to deal with in addition to the design complexities. Also, I had access to Solidworks at work. I wish they had a licensing options for hobbyists like myself, but they don’t. I realize that I’d be logging a lot of Saturday/weekend hours of my own time at the lab to get this done. I asked, and got the okay to use the lab equipment (in case you’re wondering).

Solidworks is a pretty good parametric design tool for engineering parts. I only needed to establish the constraints. This is probably the biggest hurdle. The actual design called for a lot of information that I did not have in order to start the drawing process. So the next step was to go information hunting.

The first thing I needed was her ring size. After a lot of thought and day dreaming about how I was going to get her ring size, I realized that the risk for this information was too great. It could adversely change the design. I was already working in experimental conditions, and I didn’t need more uncertainty. Usually, a ring from a manufacturer will come with some sort of guarantee that they’ll resize it for you if you’re guessing and it doesn’t fit. I had no such guarantees. I am the designer. So, I just got a ring template and just asked her directly. Everything else was still going to be a surprise, but I needed data to really give her something that’s really custom fitted to her.

Ring size chart: (http://images.zales.com/images/popups/zales_ringsizer.pdf)

How do you know that you’re in a real relationship that is leading somewhere? You can easily ask for sizes of rings, dresses, etc.

Okay, so I have her ring size. Not enough information! I needed to know the exact manufacturing process that this ring will be produced under so that I can constrain the ring diameter. Now this is where things turn complicated.

Seriously speaking, the only way that I was going to avoid having to buy a rather long list of equipment for a very short term use was to utilize 3D printing technology. Let’s just say I shopped around and looked at a lot of printing sources. The one I ended up using was Shapeways. The reason for this is the technical information. If I was going to design my own ring, I needed data on the printing process. This site has the data for me to do that kind of planning. Price was a factor, and it became a trade-off as to what I wanted to pick.

Material Resource: http://www.shapeways.com/materials/gold

The manufacturing process is pretty easy to explain. 3D printers are essentially inkjet printers that have retired from printing ink and traded in their paper for plastic. Drops of various plastics or wax can be deposited drop-by-drop in individual layers to form a solid 3D object. We have a few of those here at at work, they’re good for prototyping. In this process, a hard wax version similar to plastic is printed, then a cast is made from that model. The wax is then melted out of the mold and metal is poured in to replace it.

High resolution printing from Shapeways

This presents some interesting questions. What are the supporting wall thicknesses? What are the metal contractions and process losses? Is there sufficient resolution?

Well, the supporting wall thicknesses are posted as 0.8 mm, but actually the emboss details can be as low as 0.35 mm. Keep in mind, these are still very large values for what I’d like to do. Ring details can also be very small. I iterated through many design iterations to arrive at the printable model. I originally went to town with my imagination. A piece of candy, butterflies, then reality set in and I realized that just getting this right was going to be enough problems. Shapeways also list 10% material reduction during the polishing process. I had no idea how to measure that. The only way to find out was to actually do it, and find out.

Prototype 0

First things first. Design a ring. The above shows Prototype 0. This was more of a feasibility test model of the software and design capabilities. I needed to know how much control I had for inserting complex 3D artistic details and how much time it would take to embed those details (partly guided by real gem dimensions) on a 3D model. It looks good but there are a lot of things lacking here. Learning to wrap intricate designs on a curved round model was a challenge.

The next task was to make appropriate clearance and dimensions for the very real gems that had to fit into the grooves. Something that Shapeways did not account for was the fact that designers such as myself need walls thinner than recommended so that we can actually bend them around. Deformation, after all, is part of the process of setting. Sizing the appropriate setting was difficult. I selected for 6 prongs because I wasn’t too confident with my ability to fit as well as the 10% reduction in material difference. Better add more prongs for safety, right?