Engineering student Keren Callen shows off a 3-D printed engagement ring he made for his fiance, Maddie Mullikin.
Engineering student Keren Callen shows off a 3-D printed engagement ring he made for his fiance, Maddie Mullikin.

Keren 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 of three years, Maddie Mullikin. Just before Winter Break, Callen proposed to Mullikin by presenting her a 3-D 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 to be 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 UofL in 2007, first as a student in the Speed School, before transitioned to marketing, and then 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,” Callen said. “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.

“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,” he said.

Callen cared enough to spend 5½ months working on the ring.

“I figured that’d be a way I could show my feelings,” he said. 

As for the process, Callen first 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. Out of all the options available, he narroed it down to the 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,” Callen said.

Once that decision was final, he “extruded a basic shape” on Solid Works, took measurements from a ring Mullikin regularly wears and “went from there.” With help from Joe Vicars in the Rapid Prototyping Center, he designed a mold for the ring, which was then set in gold.

“The mold is not like a mold out of play dough. The mold is a design. To straight up 3-D 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 3-D printing website,” Callen said. 

When it came time, Callen proposed to Mullikin on campus on the first floor of the Rapid Prototyping Center. Mullikin said yes.

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. 

For more on this story, check out the video below: 

Photo courtesy of Kari Donahue.