Love in 3D: How grad student Keren Callen engineered an engagement ring

3D Printed Engagement RingKeren Callen is in love. A graduate student in the Mechanical Engineering program, Callen has found a way to blend his passion for engineering with his love for his girlfriend Maddie Mullikin. This weekend, Callen proposed to his girlfriend of three years, seven months, five minutes, and one second ago or 113,187,979 in seconds at the time of this writing, a running calculation that he has readily available, by presenting her a 3D printed ring of his own design.

Callen isn’t sure what the future holds beyond his impending spring graduation, but he knows that he wants Mullikin as part of it. Since his high school graduation, Callen has been a student in one way or another, first in the officer candidate school for the Marine Corps and later at the University of Louisville. He came to the University in 2007, first as a student in the Speed School, before transitioned to marketing, before returning in 2012 to the Speed School; the call for engineering was too strong.

Callen has long studied the science of their relationship. Although he knew that they had good chemistry, Callen had planned for months for the best moment to propose.

“She told me last May that she thought she’d be married by now. When I knew, it was shortly after that. You know what, I’ll never find anyone else in the world that’s going to tell me… I don’t even know how to word that,” says Callen.

He adds, “The mental aspect of it is a complex thing that most engineers don’t get, because it’s not based on logic. Basically everything we do has to be logical, because that’s how the world works.”

Part of his struggle was in finding the right way to express his love, while staying true to his engineering roots. He explains, “I’m not in touch with my emotional side, I figured that spending the amount of time that it took to make this ring and design it would show here that I care. A lot. Enough to spend 5 ½ months working on it. That’s why I did it. I figured that’d be a way I could show my feelings.”

Naturally it was a process. Callen had to determine what kind of ring to create, but needed more data from Mullikin. The two looked at a few rings and after identifying a few qualities that she admired, he went cautiously forward.

“It made me nervous, because I have too many options. I told her that if I get you a ring that you are equally okay with any of these options. I was stuck with emerald cut, modified hexagonal, and marquee cut. So I did my own research. Which ones did I think were the coolest? Obviously I’m into geometric shapes. There are circle cuts, round cuts… all these weird things. I picked the thing that would be most geometric, which would be emerald.”

He continues, “I sat down one day and opened up my computer and I extruded a basic shape on Solid Works. It occurred to me that I should probably take measurements, so when she took off her ring… she wears this one ring constantly, and when she took it off, I took out my calipers and took the dimensions of the ring that she had currently. I used that as my base and I went from there.”

Once he had all the pertinent info and his stylistic decisions were set, he went to work. Gaining help from Joe Vicars in the Rapid Prototyping Center, he designed a mold for the ring, which was then set in gold.

He explains of his process, “The mold is not like a mold out of play dough. The mold is a design. To straight up 3D print in gold would be an astronomical amount of money. People do it, but I can’t do that. I created the plastic version of the ring, so that I had an object to hold, and I sent off all my materials to a place called Shape Ways, a 3D printing website.”

It came down to logistics. An anxious Callen admitted that his plans were thrown off by a scheduling change over the weekend; improvising is an unknown variable. It was critical to get this moment right though, so he recalibrated. On Saturday, Callen proposed to Mullikin on campus on the first floor of the Rapid Prototyping Center, lights strung up that popped the question. Down on one knee, ring in hand, lights in the background, Mullikin said yes.

Everything fell into place. After accepting his proposal, Callen took Mullikin on a tour of the facility, leaving campus to meet up with family and friends to celebrate. Now the wedding planning has begun, and true to his nature, Callen has offered to work with Mullikin to create her own wedding band, an act of collaboration symbolic of their love.