Grand Seiko "Spring Drive UFA" New Caliber 9RB2 Achieves Ultimate Precision, Visibility, and Aesthetics

In 1969, Grand Seiko introduced the most accurate model at the time. It was called the "VFA." This model, named "Very Fine Adjusted," boasted ultra-high accuracy of within ±1 minute per month. Half a century has passed since then, and Grand Seiko's new model, the "Spring Drive UFA," aims to revolutionize the way spring-driven wristwatches are made, with an unprecedented level of accuracy of ±20 seconds per year, rather than daily or monthly.

The new Caliber 9RB2 delivers the highest level of precision, legibility, and aesthetics

　The Grand Seiko Evolution 9 Collection Spring Drive UFA model is named for Ultra Fine Accuracy. The name clearly echoes the VFA, the ultra-high-precision model that once reigned as the flagship model. There's a reason why the company didn't use the VFA name again. The previous VFA achieved outstanding accuracy through meticulous adjustment. The new Spring Drive UFA, on the other hand, achieves an extraordinary level of accuracy, with an annual deviation of ±20 seconds, thanks to a sophisticated mechanism. The difference in name reflects Grand Seiko's maturity.

　Spring Drive, which combines the powerful torque of a mechanical movement with the high precision of a quartz movement, is the perfect movement for Grand Seiko. Grand Seiko achieved an accuracy of ±10 seconds per month with the 2020 Caliber 9RA series, and this year's 9RB2 surpassed the annual accuracy barrier. This is without a doubt the world's highest accuracy for a mechanical watch powered by a mainspring.

　However, it seems Grand Seiko has made this new model, equipped with the 9RB2 movement, into a "usable watch." Visibility is excellent thanks to the thick hands and indices. The bright titanium and platinum case is small, measuring just 37mm in diameter, making it perfect for everyday wear. Furthermore, the bracelet features a new fine-adjustment buckle, further improving the wearing comfort.

　The Evolution 9 Collection Spring Drive UFA combines unprecedented precision with a package suitable for everyday use. Its extremely unique construction exemplifies the one-of-a-kind nature of Grand Seiko.

The secret behind the Caliber 9RB2's accuracy of ±20 seconds per year

The biggest topic of conversation is the caliber 9RB2, which boasts an extraordinary level of precision, with an annual deviation of ±20 seconds. Grand Seiko's 9R Spring Drive movement, which began with the caliber 9R65 in 2004, has finally achieved an extraordinary level of precision for a spring-powered wristwatch. This was made possible by a tireless commitment to improving precision, which began with the 9F Quartz movement. How did the development team achieve this extraordinary level of precision?

　Spring Drive has long been Grand Seiko's third engine. Combining the powerful torque of a mechanical movement with the precision of a quartz movement, this "engine" was the perfect movement for Grand Seiko, which demands high visibility and precision.

　In 2020, Grand Seiko announced a new generation of Spring Drive movements. With a long power reserve of approximately five days and high accuracy of ±10 seconds per month, the Caliber 9RA series was worthy of being called the pinnacle of Spring Drive. However, Grand Seiko continued to develop even higher-precision models. This was the Caliber 9RB2. The 9RA series achieved ±10 seconds per month by repurposing the temperature compensation function of the masterpiece 9F Quartz. Quartz, the heart of Spring Drive, loses accuracy when temperatures deviate from 25°C. Grand Seiko further improved accuracy by adding temperature compensation using an IC. However, performing temperature compensation 540 times a day increases power consumption. Who would have imagined that this feature, previously thought impossible to incorporate into a low-power Spring Drive?

　In theory, the 9RA series could have achieved yearly accuracy, but Grand Seiko limited itself to a monthly accuracy of ±10 seconds. This was because they had already developed the 9RB2, which could achieve yearly accuracy. The 9RA series also features an IC with added temperature compensation and a quartz crystal unit housed in a vacuum package. However, the quartz crystal manufacturing method was changed to stabilize quality, and the 9F quartz crystal was aged for a long period, just like the 9RA quartz, to slow the aging process. Only the selected crystals were used in the product.

　Eiichi Hiratani of Seiko Epson has developed Spring Drive watches for Grand Seiko, including the 9RB series as well as the 9RA series. "Because the 9F quartz movement has a high voltage, we were able to add a temperature compensation function to the IC. However, the voltage and current of Spring Drive is one-sixth that of the 9F quartz movement. Installing this in the 9RA series was difficult." Hiratani also combined the quartz oscillator, which had previously been arranged separately from the IC, into a vacuum package, making it easier to transmit compensation information.

　This is where the newness of the 9RB2 begins. To ensure they are aiming for the same year-to-year difference, the engineers have made further improvements. One of these is the manufacturing method for the crystal oscillator. "Under the previous manufacturing method, a slight amount of stress remains inside the crystal oscillator. When this distortion is gradually released, the frequency of the crystal oscillator changes, causing it to go out of alignment," says Hiratani. To obtain a heart that is less susceptible to deviation, the entire manufacturing method, including the cutting method, has been improved.

　Even with all these measures, there is still a possibility that the watch will lose or gain time. That's why Hiratani and his team of engineers added a regulator switch to the 9RB2, which can adjust the time, just like a mechanical watch. In other words, in addition to adding functions to ensure accuracy, they also added an adjustment function as a "safety mechanism" just in case. The regulator switch, which can be adjusted in 12 steps in total, with each step being able to adjust the time by seconds per year, was a major key to achieving reliable annual accuracy. Hearing about the efforts that have gone into this, it's no wonder Hiratani said, "The 9RA series is a movement that has been perfected to achieve monthly accuracy, while the 9RB2 is a movement that achieves annual accuracy."

　What's more, the 9RB2 is compact enough to fit into a case with a diameter of 37mm. This is also an attempt at something "out of this world."

Taking on the challenge of further miniaturization and thinning

The Caliber 9RB2 incorporates various mechanisms to achieve an annual accuracy of ±20 seconds. However, the movement is thinner and more compact than the Caliber 9R65 from 2004. Moreover, it maintains a power reserve of approximately 72 hours. The key to successfully overcoming the conflicting elements of high precision and compactness and thinness is the know-how accumulated over more than 20 years of Spring Drive development.

　The Caliber 9RB2 boasts undoubtedly the world's highest accuracy among mass-produced spring-driven watches. However, what is also remarkable about this movement is its compactness. Spring Drive uses the unwinding force of the mainspring to move the hands, and the excess power generates electricity to operate an IC and vibrate a quartz oscillator, rotating the hands at a constant speed. The reason it keeps time far more accurately than mechanical watches is thanks to the high frequency of the quartz oscillator and the precise control provided by the IC. However, this comes at the cost of its size: the Tri-Synchro Regulator, its heart, takes up nearly half the clock's space. Seiko Epson's engineers' challenge was to achieve high accuracy of ±20 seconds per year in the smallest possible size. Considering its high performance, the 9RB2's 30mm diameter and 5.02mm thickness are astonishing.

　The first thing the engineers tackled was combining the two mainspring barrels in the 9RA series into one. While this may seem simple at first glance, a drop in mainspring torque would cause the Spring Drive to lose power and stop. Therefore, a new approach was chosen: cramming a long, thin mainspring into an extremely large 14.5mm diameter barrel. To slim the movement, the barrel itself was kept just 1.2mm thick. Reducing the height and thickness of the mainspring would reduce torque, making it insufficient to power not only the quartz crystal oscillator but also the temperature-compensated IC. However, Seiko Epson's continued pursuit of power saving led to this unprecedented approach. This is evidenced by the significantly higher speed-up ratio from the mainspring to the wheel train—8.5 to 9, compared to the 7 to 7.5 ratio of conventional mechanical watches. In other words, despite the watch's higher performance, the power reserve is extended by slowing down the mainspring's unwinding speed. "The official power reserve is about 72 hours, but it's designed to last nearly 100 hours," says Hiratani.

　Even individual components were reviewed. For example, the Magic Lever automatic winding system, which transmits the rotation of the oscillating weight to the mainspring, was 30% smaller than the 9R6 series, while changes to design parameters and the use of a tungsten-based oscillating weight improved winding efficiency.

　Advances in the circuitry itself also contributed to the small 37mm case diameter. Spring Drive watches, which have electronic circuits built into their movements, are theoretically vulnerable to magnetism. Previously, this was addressed by adding a soft-iron anti-magnetic ring that also served as a retaining ring to the outside of the movement. However, by distributing the role of the anti-magnetic ring within the movement, the 9RB2 eliminated the need for an extra ring. Having the anti-magnetic components tucked inside the movement made watch assembly more difficult. However, for Seiko Epson, where design, manufacturing, and assembly are all handled in-house and with close coordination, this was no difficult task.

　The unique oscillating weight is also a factor in the slimming and compact design. The large hollowed-out center was designed for aesthetic reasons, and to increase the inertia during rotation while making the oscillating weight thin and light. By making the entire oscillating weight out of a hard, heavy tungsten alloy, it was possible to achieve aesthetics, a thin design, and high winding efficiency.

　In addition to its high accuracy of ±20 seconds per year, the 9RB2 was newly designed to fit into a small case. This masterpiece is the culmination of Grand Seiko's philosophy of maintaining high standards in everything.

Exterior design that pursues visibility, aesthetics, and comfort

With this new model, equipped with the Spring Drive UFA movement, the brand aimed to further refine its Grand Seiko identity. To that end, the design, based on the Evolution 9 style, has been further refined to further improve legibility, aesthetics, and comfort. It's not just the contents that matter, but the overall package that matters with this watch.

　The Evolution 9 Collection has become the face of Grand Seiko. In addition to the three-dimensional design and high legibility that are characteristic of Grand Seiko, the thin, low-center-of-gravity case and wide bracelet provide excellent comfort, raising the bar for Grand Seiko. The design of this new model also follows the Evolution 9 style. However, the case size is 3mm smaller than the SLGA021. "The SLGA021's 40mm diameter is actually a fairly compact design," says Akira Yoshida, who has been involved in Grand Seiko design. "In terms of thickness, we aimed for the thinnest possible design while maintaining robustness and water resistance. However, considering Grand Seiko's functionality and after-sales service, there was a limit to how thin we could go. In fact, it is 0.4mm thinner than the SLGA021, but considering the aspect ratio, the new case is smaller, so it feels slightly thicker in comparison."

　Normally, this would make the watch look bulky, but the clever thing about the design is that it doesn't feel that way at all. The two cases look similar, but are completely different. Yoshida worked on the treatment of the case sides. The design itself is the same as the SLGA021, but to avoid the feeling of thickness, he made the sides thinner and the lower slope slightly thicker, which makes the case appear thinner.

　The crystal is a box-shaped sapphire crystal, giving it a three-dimensional appearance. However, it is not so three-dimensional that it looks retro, and it is also characterized by its sharp corners to ensure visibility is not impaired even when viewed from an angle. As a result, the thickness of the bezel has been reduced, and the outer edge of the dial has also become thinner. Furthermore, by reducing the height of the bezel, more light can be absorbed onto the dial.

　In addition, to achieve the large dial with a wide opening and the design of the long hands, a structure was adopted in which the movement with the hands attached is attached from the crystal side. Normally, a movement with hands is casing from the back side of a middle case with a crystal, but in order to achieve a design with a wide opening, the time-consuming structure of setting the movement with hands from the crystal side and fixing it from the back side was chosen.

　The attention to practicality is also outstanding. The bright titanium model features a buckle with three-stage slide adjustment in 2mm increments. It took three years to develop, and despite being made of titanium, it feels very comfortable to operate. The fine-adjustment clasp has also been tested for 4000 slides (4000 back and forth), so it's highly durable.

　The width of the bracelet is a testament to Grand Seiko's insight. At 20mm on the case and 18mm on the buckle, it's a good, normal size considering that many bracelets today are tapered at the buckle. While tapering can make a watch look dressy, it can also make it feel heavy on the head. This style of tapering, while still maintaining practicality, is a perfect balance for Grand Seiko today. Combined with the light material, it makes for an even better fit.

　The three-dimensional dial, a specialty of the brand, has also been evolved. This time, the motif chosen for the dial is the frost-covered forests of Shinshu, where Spring Drive is manufactured. Designer Yoshida explains that the thin layer of ice-covered coniferous forests seen on the Kirigamine Plateau was superimposed on the ultra-high precision of the Caliber 9RB series and the silent operation of Spring Drive. As with previous models, the deep pattern is applied by pressing. However, by deliberately adding a honing process to the surface finish, the base is kept semi-matt. This is why the indexes do not become buried despite the strong pattern.

　The dial paint was also ingeniously designed. A pearlescent paint was sprayed underneath the clear layer on the surface, expressing the glittering flurry of thin ice that has been torn off from the frost-covered forest by the wind. Applying pearlescent paint underneath a clear coat is rare, and even among Grand Seiko, there are few examples where the sparkle of fluttering thin ice is expressed by spraying a faint layer of pearlescent paint on a pale blue surface.

　The Spring Drive UFA stole the show at this year's watch fair with its extraordinary precision of ±20 seconds per year. Of course, the movement, Caliber 9RB2, which actually achieves ultra-high precision, is outstanding. However, what's even more impressive is Grand Seiko's skill in skillfully putting together this ultra-high-precision watch. The ability to bring all the elements together to such a high standard is what makes this year's new releases the highlight of the show.

　This new model is by no means a racing machine boasting only precision. It is a luxury watch for a new era that, despite its ultra-high performance, doesn't feel like it.