We provide customized case processing services to customers all over the world:The watch case usually refers to the shell parts of the watch body (head), its function is to contain and protect the internal parts of the watch (movement, dial, hands, etc.), and the parts closely connected with the watch case are: watch mirror, bottom cover , crown, buttons, etc.
RICHARD MILLE released an upgraded version of their sapphire crystal case, RM 056-01, at S.I.H.H. in 2013. In addition to the case, the base plate, the central plywood and the three-wheeled car are also made transparent, and the whole watch is made of light. Just like being invisible, it's terrifying. However, in retrospect, compared to the transparent case, many people have made the transparent movement before this. In the past two years, Baoplatin has produced a transparent carrousel, and Kunlun has also produced a transparent tourbillon. The technology of the RM 056-01 is not the same, but the RM 056-01 is slightly inferior to the 2012 RM 056, which shocked the audience as soon as it was launched.
Sapphire crystal is difficult to process, but the information provided by various brands is limited. I read a foreign report and interviewed Stettler Sapphire AG, the foundry of the RM 056 case and the supplier of watch mirrors for several major Swiss brands. It introduced in detail the process they helped RICHARD MILLE build the sapphire crystal case. The content information is quite rich.
Stettler was founded in 1881. In the early days, it mainly produced gemstones for movement bearings. In the 1970s, sapphire crystal became the main material for watch mirrors. Stettler also began to produce sapphire crystal. At present, 3/4 of the company's business is related to watches and clocks. Industry-related, in addition to the mirror, the processing of sapphire crystal dials and ceramic cases is also within their business scope.
In the era of acrylic watch mirrors in the past, the watch mirrors often used the so-called box type or dom type style. This is because the strength of acrylic is relatively poor, and it must be increased by increasing the thickness or dispersing the stress on the spherical surface. The strength of the watch mirror; the era has entered the sapphire crystal. Due to the high strength of the material itself, it does not need to be strengthened by modeling and is durable. However, on the other hand, because of the high hardness of the material, it is relatively difficult to process, so there is a long period of time. The time sapphire crystal mirrors are all flat and simple shapes.
In the 1990s, Swatch Group began to invest in related technologies, and the sapphire crystal mirrors also began to have large curved surfaces such as dom. However, on the one hand, this technology was almost monopolized by Swatch Group, and on the other hand, the cost of processing itself was extremely high—— Even today, the cost of machining a dom-style crystal is still three times that of a flat one, so the development of sapphire crystal processing technology in watchmaking has been rather slow. After 2000, the application of multi-axis CNC equipment in sapphire crystal processing has become more common. Although the changes are still limited, the mirror can finally be said to have entered the three-dimensional era.
Almost ten years ago, Stettler once took an order from another weirdo, Alain Silberstein, who also wanted a sapphire crystal case, so strictly speaking, their family has not handled such cases, but Xiao Burstein’s case is so straight through, and the difficulty of processing is relatively simple (but still difficult). Compared with the requirements put forward by RICHARD MILLE this time, Stettler is really facing an unprecedented new challenge.
At the beginning of receiving the order from RICHARD MILLE, Stettler was not quite sure how difficult it was to make this batch of goods.
First is the raw material. At present, there are several methods of making sapphire crystal raw materials in the industry, such as the "Verneuil method" and the "Czochralski method". Basically, the alumina is heated and melted for a long time and then crystallized. However, in the Verneuil method, like this The raw material made by the original method can only be a watch mirror with a diameter of 40mm, which is still too small for the case to be made this time, so they purchased another batch from Russia with another "EFG method". Made of large sapphire crystal.
Next is cutting. To deal with such a complex watch case, the general processing equipment is simply not up to the task. For this reason, Stettler specially introduced two 5-axis CNC machines with ultrasonic motors. Each of these two machines costs 800,000 Swiss francs. How heavy is the book this time.
Like diamonds, sapphire crystals have so-called "axes", and these axes should be avoided during processing, otherwise the raw material will easily be broken. In terms of the size of the mirror, one has almost 50 axes, but it doesn't matter if you don't care about the flat mirror, but there is no way to make the case like this time. It seems that a piece of transparent raw material recognizes those axes one by one and carefully avoids them.
The hardest part is opening the holes. They use a diamond drill bit to drill at 10,000 rpm; an electric drill can spin up to 40,000 rpm, but a lower speed is used to prevent the drill from overheating, but once the temperature exceeds 900 degrees C Pause and wait until the drill cools down before continuing. Another trick is to make a smaller hole first, and then slowly drill down to make it bigger, so it's less likely to crack. When the interviewer asked if they had modified the original design for processing, Stettler said they had not, because the original condition of Richard Mille was not to change any design.
Last is sanding. Stettler grinds the finished case with free diamond powder—putting the case into a closed device, where diamond powder will be ejected to hit the surface of the case to achieve the grinding effect; grinding from 10 microns Grind all the way down to 2-3 microns, then do chemical treatment at the end, and then coat the surface with silicon. So far, the case of RM 056 is a success, and it is understood how difficult it is to make this fully transparent sapphire crystal case. There is some truth to the limited number of 5 pieces in the world and the high price.