For the premium watch maker IWC Schaffhausen innovations are the basis for success. This applies to their own watches as well as to their manufacturing process. It is therefore no surprise that high-accuracy machining centers from Kern Microtechnik dominate the milling part. A partnership at eye level that results in ongoing improvements in productivity and innovations. Most recently, IWC invested in five high-end Kern Micro HD machining centers.
It quickly becomes clear when entering the halls of IWC International Watch Co. AG in Schaffhausen that manufacturing and automated precision do not contradict each other but complement each other excellently. Because the Swiss manufacturer of exclusive luxury watches - costing between €5,000 and €750,000 - masters this combination like few other companies. While assembly is carried out by master watchmakers in intense manual labor according to the old tradition, automated precision-machining centers are primarily used in machining production.
IWC has been working according to this principle since it was founded in 1868. At that time, Boston-born watchmaker Florentine Ariosto Jones deliberately chose Schaffhausen, Switzerland, as his location. Heiko Zimmermann, responsible for the industrialization of part production, milling center, at IWC, says: “There has always been a lot of hydropower in Schaffhausen. This energy source was reason enough for our company founder to build his company here. He already recognized at that time that it could be used to operate machines, which ultimately led to a productivity advantage. An innovative vision that still shapes the thinking in our company today.”
Up to 220 processing steps on a few square centimeters
While IWC only produces a few individual pieces per year in the highest six-figure price segment, the Swiss company produces tens of thousands of watches every year in the “inexpensive” four-digit euro range. The materials used and the number of functions to be integrated, such as tourbillon, perpetual calendar, or moon phase display, are correspondingly different.
A total of just ten watch plates with a diameter of 30 mm to 40 mm are the basis for all IWC watches. All parts of the movement (known in technical jargon as the caliber) are placed on them - from the bridge to all the pins, axles and gears to the bearing jewels made from industrial rubies. Depending on the complexity, 80 to 220 features have to be added to the watch plate - primarily by drilling, milling and threading.
Tasks that can only be carried out with automated high-precision machining centers to guarantee repeatable accuracy, process reliability and an economic process. Around 40 to 70 different tools are used per plate. In order to limit the number of tool changes and at the same time increase productivity, IWC has been using a four-fold clamping device for several years. However, still around 750 tool changes per day and machine are necessary.
There is no alternative to reliably maintain the exact position and height during the entire manufacturing process. In numbers: The required position tolerance is <10 µm, which means a deviation of less than 3 µm to 4 µm for the X and Y axes. There is also a tolerance of <10 µm in the Z axis, but this refers to the front and back side of the watch plate. The challenge here lies primarily in compensating for the growth in length of the milling spindle, Zimmermann makes clear and adds: “The many different speeds and the part distortion have a major influence here. We are therefore pleased to have a partner in Kern Microtechnik who can solve all of these challenges.”
Kern Microtechnik, a reliable problem - solver
The luxury watch manufacturer has been relying on the know-how and technology of Kern Microtechnik GmbH for 25 years. In 1999, the Swiss bought the three-axis Kern HSPC, the first precision-machining center from Eschenlohe. According to production manager Christian Indlekofer, what was crucial back then was the high precision of the machine, which was also proven in a practical benchmark test.
“In 2015, we expanded our production with the five-axis Kern Micro Vario and have always been in close contact since then,” says Indlekofer: “Above all, the close and steady exchange between our industrialization manager Heiko Zimmermann and the Kern area sales manager Stephan Zeller also led to our most recent investments – five Kern Micro HDs in the last five years.”
Before purchasing it, those responsible at IWC carried out extensive tests with this high-end machining center and compared it with various other machines - including the Kern Micro Vario. According to Heiko Zimmermann, the result was clear: “The additional costs for the HD are paid off in less than twelve months due to the higher performance and further increased quality.”
Each machine has an individual fingerprint
Regardless of whether 80 or 220 machining operations need to be carried out - the five-axis Kern Micro HD completes all steps in one clamping and achieves an average position deviation of less than 0.5 µm. The max permissible deviation of 2 to 10 µm are therefore 100% guaranteed. On the one hand, this is due to the hydrostatic guides, the actively temperature-controlled linear motors, and the innovative temperature management. On the other hand, the machine reliably compensates for any changes with its individual “fingerprint”.
Kern expert Stephan Zeller explains what is behind the fingerprint: “During commissioning in Eschenlohe, each machine “learns” its individual thermal “fingerprint” in relation to its specific behavior in all speed ranges and under a wide variety of conditions. We save the results in the said fingerprint. When in use at the customer on site, the machine then constantly records the manufacturing conditions, compares them with the fingerprint database and adjusts crucial parameters such as the length growth of the spindle in the nano range.”
Angling – productive feature as a result of close cooperation
The commitment of all Kern employees and the ongoing new developments of the machine manufacturer from Eschenlohe impressed Heiko Zimmermann and his production manager Christian Indlekofer from the very beginning of the collaboration. Zimmermann und Indlekofer are even more enthusiastic about the team at Kern turning even individual wishes and suggestions into solutions. “We regularly have conversations in which we always come across interesting new approaches,” says Zimmermann. As the most recent example, he cites the new Kern Micro HD’s “Angling” function, which has been around for approximately a year. “This option allows us to facet edges using a diamond tool – which does not rotate but follows the contour – by plaining them, so to speak. This allows us to achieve surfaces with a level of gloss that corresponds to a polish.”
In addition to the software function created by Kern, the hydrostatics and the linear drives of the Kern Micro HD are crucial for the successful implementation. This gives the Kern machine the necessary stability and prevents stick-slip effects, which would lead to visible surface injuries. Angling is important, not least because there are fewer and fewer polishing specialists, says Indlekofer: “Apart from that, it obviously saves us valuable employee time and increases the productivity of our production even further.”
Automated machining centers run 24/7To ensure that high-tech production in Schaffhausen runs around the clock, even though employees work single shifts, IWC has equipped all machines with robot-assisted automation and a large workpiece storage. The operators set up their machines before the end of the shift and only have to remove the finished parts at the start of the new shift. With the high reliability of the Kern machines, this works not just over two shifts, but over the entire weekend. “More utilization is not possible,” say Christian Indlekofer and Heiko Zimmermann equally happily.
More information about the company, technology and products is available at KERN Microtechnik GmbH.