Watch oscillator
Wattwins 2DOF time-base oscillator
The Instant-Lab at the Swiss Institute of Technoloy of Lausanne (EPFL) is developing Wattwins 2DOF time-base oscillator for mechanical wristwatches without escapement (IsoSpring concept), machined in silicon by DRIE, with 4 gold masses. Measuring both in- and out-of-plane displacements of its elements is of first importance for minimizing losses and optimizing the efficiency of the mechanisms.
Reference:
H. Schneegans, E. Thalmann, S. Henein,
Shaking force balancing of a 2-DOF Isotropic horological oscillator,
Precision Engineering, Volume 72, 2021,, Pages 502-520, ISSN 0141-6359,
https://doi.org/10.1016/j.precisioneng.2021.06.003
The outer diameter of a Wattwins oscillator is 30 mm.
A macro DHM® enables therefore to capture the full oscillator surface with a single camera acquisition.
This single capture provides the 3D topography of the sample, as shown on the left. In this representation, colors encodes surface height.
As such measurement is performed at camera rate, continuous camera recording enables to measure the 4D topography of the sample.
Intensity (left) and 4D topography (right, isolevel contours, equidistance: 333 nm, 3 lines = 1 micrometer) versus time are shown on the right movie.
All components and flexures of the oscillator can be segmented using the intensity information. Their in- and out-of-plane position, tilt/tip angles, and deformation versus time, as well as their resonances can be measured.
The XYZ+time motion of the element that connects the oscillator to the rest of the watch movement is shown in the left movie.
It is decomposed into pure in- and out-of-plane motions in the movies here below.
The displacements measured in this example are not associated with a sustained movement, but are generated by a shock on the mechanism. Damping parameters can be determined, and a Fourier transform of this time response enable to analyze the resonance frequencies.
This analysis can be made on any of the components of the Wattwins oscillator.
Silicon based watch oscillator
Watch industry is developing new innovative product using silicon based technology. Such parts are adapted to DHM® inspection both at component level or wafer level.
Description
- Courtesy of : LVMH Watches, R&D department
- Material : Silicon
- Size : ø 34mm
- Instrument : Macro DHM
- Frame rate : 190 fps camera
- Field of view : 32 x 32 mm
Measurement
The goal of the measurement is to evaluate the out of plane displacement of the oscillator during one cycle. The DHM® is measuring the dynamic topography, this unique set of data includes both rotation and out-of-plane information.
Image processing enables image registration to focus on out of plane vibrations. The amplitude map bellow shows the out-of-plane vibration amplitude on the entire image when the plot shows the temporal evolution of the out-of-plane displacement in nanometer.
