Watch Case Optimization with Numerical Simulation Tools

The Swiss “Maison de Haute Horlogerie” Czapek & Cie, founded in 1845 by François (Franciszek) Czapek, a Polish watchmaker of Czech origin who arrived in Geneva in 1832, and relaunched in 2015, embodies artisanal excellence and innovation.

Czapek is positioned as a “connoisseur” brand and occupies the Independent Fine Watchmaking segment. It establishes itself as an alternative to the brands of the “Holy Trinity” (Patek Philippe, Vacheron Constantin, Audemars Piguet) and is positioned at the level of high-end independents such as H. Moser & Cie or Parmigiani Fleurier.

The models are distinguished by a blend of 19th-century aesthetics (Roman numerals, Fleurs de Lys hands) and radical modernism (architecture of the SXH5 calibre with its skeletoniszed gear train bridges).

Casing Design, Watchmaking Simulation, and Material Selection to Celebrate 10 Years of Revival

To celebrate its tenth anniversary since revival, the brand imagined an exclusive anniversary collection based on Calibre 10.01, named "Time Jumper". This project, combining tradition and technology, required complex technical optimization carried out in partnership with CADFEM using Ansys simulation tools and material selection via Granta Selector. The objective was to improve the opening mechanism of a watch cover rapidly, as the product had to be presented to the public within a very short timeframe.

The 10th Anniversary Collection "Time Jumper". | © Czapek & Cie SA

How CADFEM Facilitated the Realization of This Case Project

To meet these challenges, CADFEM implemented an approach based on digital simulation with three flagship tools:

• Rapid geometry preparation and adaptation with Ansys Discovery
• Non-linear finite element analyses with Ansys Mechanical

• Selection of the appropriate material with Ansys Granta Selector, for optimal resistance and increased durability.

By relying on the one hand on iterations between the tools and on the other hand by combining the engineer’s intuition and expertise, it was possible to optimize the shape of the spring and validate its mechanical behavior under simulated conditions close to reality.

Indeed, the initial solution presented significant issues with unwanted contacts, limited opening force, and premature wear. A new concept using a single spring instead of two separate springs was therefore proposed. The main challenge was to design a spring capable of providing sufficient force while maintaining a compact design, meeting both production and usage constraints.

Distribution of equivalent von Mises stresses in the spring at mid opening/closing stroke. | © Czapek & Cie SA

It was therefore necessary to simultaneously increase the force level and eliminate all unwanted contacts while respecting the working volume and predefined attachment points. Digital simulation proved ideal to meet such a challenge by enabling rapid testing of multiple solutions while limiting development costs for a limited series model.

Thanks to Granta Selector software, the choice of a specific steel both resistant to salt spray and with a high yield strength was key to finding a solution. The limited working volume, predefined attachments, and support point positions in open and closed configurations left little room for maneuver to meet material strength constraints.

Numerous iterations made it possible to optimize both the spring profile, the position of the contact point, and the contact geometry with the cover. Thus, a spring ensuring sufficient opening force in all positions, while exhibiting a homogeneous stress distribution, was designed – the key to remaining within the material’s elastic limit.

Ashby plot showing mechanical properties of materials prefiltered by production and durability constraints. | © Czapek & Cie SA

Based on initial physical tests, with very satisfactory results, the introduction of an alternative cover with an increased weight of nearly 90% was considered. After redefining production constraints, a shift of the attachment points was examined to increase the available working volume. The loss of stiffness due to the increased length was compensated by adapting the cross-section while limiting local deformations and stresses.

Eventually, after numerous iterations using simulation software, a spring solution was proposed. This spring is now capable of generating the required, higher force while meeting the other constraints.

Simulation Results Obtained Quickly for Decision-Making Based on Reliable Data

The results obtained are significant:

• Optimized opening force, exceeding gravity force by 30% while maintaining acceptable stress levels.
• Unwanted contacts are avoided, thereby eliminating premature wear.

The use of digital simulation increased reliability, reduced wear risks, maintained an aesthetic and functional design, and enabled decision-making based on reliable data.

For the engineers at Czapek & Cie, all these exchanges translated into a significantly reduced number of physical prototypes, generating substantial time savings while delivering a functional solution that ensured the product could be presented as planned.

In practical terms, the benefit of these analyses was assessed by Czapek operators as a saving of between two and five spring prototypes. Thanks to simulation, a spring free of friction and/or unwanted snagging was developed rapidly. Ultimately, this entire development process significantly improves the wearer’s experience of the "Time Jumper" and increases the model’s chances of success.

Simulation Is the Future Solution for Czapek

This project perfectly illustrates how digital simulation and intelligent material selection can support innovation in high watchmaking.

The dynamic opening of the cover of this new Czapek watch, thanks to the spring designed in collaboration with CADFEM, does justice to its name: “Time Jumper”.

Building on this success, Czapek is considering continuing its collaboration with CADFEM to optimize other components and further integrate simulation into its development process. This iconic company wishes to continue combining tradition and technology, in the service of the watchmaking excellence of which it is the heir.