Watch Hairspring Stiffness Correction via Iterative Material Removal
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Solution Overview
Problem
The micro-manufacturing of watch hairsprings faces significant geometric dispersion in dimensions and stiffness due to etching processes, leading to variability in natural frequency, which complicates the pairing with balance wheels and requires precise correction steps, slowing down production and necessitating sampling for characterization.
Innovation Solution
A process involving forming hairsprings to predetermined dimensions, evaluating their stiffness, and iteratively modifying dimensions by adding or removing incremental material to achieve a target tolerance range, rather than precise thickness calculations, allowing for a qualitative validation approach that simplifies the production flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If precise thickness calculations and corrections are applied to each spiral, then manufacturing precision is improved, but production time increases and productivity decreases
Solution Approach 1:
The patent applies partial correction by only adjusting the thickness of spirals that fall outside the target stiffness range, rather than correcting all spirals to exact specifications. This selective approach maintains manufacturing precision for defective items while avoiding the time-consuming process of precise calculation and correction for all items, thereby improving productivity.
Solution Approach 2:
The patent implements a feedback mechanism where the stiffness of each spiral is measured, and based on this measurement, a correction is applied only if the stiffness is outside the target range. This iterative feedback loop ensures precision for affected items while avoiding unnecessary correction steps for acceptable items, resolving the contradiction between precision and productivity.
2Manufacturing precision
If sampling is performed to characterize spiral properties, then manufacturing precision is improved through statistical control, but production time increases
Solution Approach 1:
The patent applies preliminary action by establishing target stiffness ranges and correction protocols before production begins. This pre-planned approach eliminates the need for extensive sampling and statistical analysis during production, as the criteria for acceptance and correction are predetermined, thereby reducing time loss while maintaining precision.
Solution Approach 2:
The patent enables self-service by allowing the manufacturing process to automatically identify and correct defective spirals based on measured stiffness values, without requiring continuous sampling and external intervention. The system self-regulates by comparing measured values against target ranges and applying corrections only when necessary, reducing time consumption while maintaining control precision.
3Manufacturing precision
If geometric dispersion is reduced through precise corrections, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying only the thickness parameter of spirals that require correction, based on their measured stiffness values. This targeted parameter adjustment simplifies the correction process compared to comprehensive dimensional control, as it focuses modification only on affected dimensions rather than implementing complex multi-parameter control systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables faster production with reduced sampling needs and more individualized correction of hairsprings, stabilizing their stiffness within a predefined tolerance range, thus improving manufacturing efficiency and reducing geometric dispersion.
Implementation Method 1
a resonator, a component that can be elastically deformed and whose oscillations determine the watch's accuracy
Implementation Method 2
Temperature variations in the Young's modulus are compensated by a layer of amorphous silicon dioxide (SiO2) surrounding the core(s), silicon being one of the few materials with a positive thermoelastic coefficient
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~3D
AI summary
The invention relates to a method for manufacturing watch balance springs, comprising the steps of: - a. forming a plurality of balance springs in a plate according to predetermined dimensions, - b. evaluating the stiffness and/or a dimension of at least one of said balance springs, - c. modifying the stiffness and/or the dimension of at least some of said balance springs, by removing or adding an incremental and predetermined quantity of material, - d. repeating step b. and possibly step c. if the result of step b. indicates that the stiffness and/or the dimension is not within a predefined tolerance range.