Kigumi is a traditional wood joinery technique known for both its structural strength and beautiful appearance. Employed in the construction of ancient shrines and temples in Japan, it has been passed down from one master artisan to the next since the 8th-century Nara period. How was Casio able to build kigumi-inspired structures into this special MR-G dial design?

Norifumi Ishiyama, an engineer at Casio with deep knowledge of molding technologies, immediately sensed the difficulty of incorporating such a sophisticated design into a finished product, he says.

“Right from the beginning, when the designer approached me with this concept, I knew it would be very tricky to craft componentry this intricate. But tough challenges have never stopped our development team before, so we got right to work on it, identifying the issues we’d have to solve before this watch could actually be built. The first big hurdle we saw was the issue of weld lines.”

Generally speaking, components manufactured with injection molding often end up with distortions or other surface issues , even when they are simply shaped. But Yamagata Casio’s advanced proprietary technologies have solved these issues, delivering beautiful forms with flawless surface textures.

The MRG-B2100, however, posed a new level of challenge. To successfully mold the numerous tiny openings in its latticework-inspired dial, a highly uniform surface finish would need to be maintained throughout the process of pouring resin into the mold. The first obstacle this presented was dealing with weld lines. Also known as knit lines , these issues can appear where resin melt flows converge, in the process of injection molding, leaving visible lines on the finished surface.

Resin can flow together in one direction without diverging when the shape being molded has no holes or openings in the surface. This dial, though, with its complex latticework form, involves multiple points where the resin flows tend to diverge and reconverge during molding. Weld lines, which would impact the uniformity of the injected resin and cause unevenness in the finished surface texture, would of course be out of the question for the flagship MR-G line, with its uncompromising commitment to a sophisticated appearance of the finest quality.

“For months after embarking on the process of development, I found myself puzzling over this issue of weld lines, day and night. I ran simulations over and over again, using flow analysis software. During this stage, I experimented with dozens of patterns for the gating system, through which the resin flows, and made minute adjustments to the diameters of the runners, or channels that feed into the gates.”

Despite all this effort, the concern remained that, when pouring in the melted resin from multiple directions, it would converge in problematic ways amid the intricate series of intersecting points in the latticework pattern, rather than spreading out uniformly. Eventually, though, the team’s hard work paid off — they considered every conceivable solution, taking into account the timing of injection and many other factors, and found a way to ensure quality worthy of the MR-G name.

“I was so nervous when we first attempted the actual molding. As we started, I was really worried that, despite all of our simulations and adjustments, it still might not work. But it did! We had mastered the challenge, and it was an amazing moment when we finally saw the success.”