Ophthalmic Lens Beveling Ridge Prediction
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Solution Overview
Problem
The existing methods for shaping ophthalmic lenses to fit eyeglass frames, particularly strongly cambered lenses with rectilinear outlines, suffer from a 'paring away' phenomenon during the beveling process, leading to reduced accuracy and quality of lens mounting due to the large radius of the beveling grindwheel, which inadvertently machines excess material.
Innovation Solution
A predictive calculation method is developed to simulate the shape of the engagement ridge on the ophthalmic lens before machining, allowing for a corrected path setting for the beveling grindwheel to minimize material removal errors and ensure proper fit, involving steps to determine initial and secondary approximations of cross-section shapes and intersections to estimate the final shape of the engagement ridge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a beveling grindwheel with large radius is used to machine the engagement ridge, then the grindwheel can cover a broader area and complete the beveling operation, but it causes the 'paring away' phenomenon where excess material is inadvertently removed and the bevel becomes thinner
Solution Approach 1:
The patent applies preliminary action by calculating and determining the corrected path setting for the beveling grindwheel before the actual beveling operation. The method computes the simulated shape of the engagement ridge by determining intersections of the grindwheel with the lens at multiple positions along the path, allowing the system to predict and compensate for material removal in advance, thus preventing the paring away phenomenon while maintaining the benefits of a large-radius grindwheel.
2Productivity
If the beveling grindwheel follows the initial path setting directly, then the machining process is simple and fast, but the final shape of the engagement ridge deviates from the desired shape due to the paring away effect
Solution Approach 1:
The patent performs preliminary calculations to determine the corrected path setting before machining. By computing the simulated shape at multiple positions and finding intersections, the system预先 (in advance) adjusts the path to compensate for expected material removal, ensuring both operational efficiency and shape accuracy are achieved without requiring complex real-time adjustments during machining.
Solution Approach 2:
The patent implements a feedback mechanism where the simulated shape calculation based on grindwheel-lens intersections provides information about the expected final shape. This simulated result feeds back into adjusting the path setting, creating a closed-loop system that ensures the actual machining produces the desired engagement ridge shape while maintaining productive machining speeds.
3Manufacturing precision
If a corrected path setting is calculated using multiple approximations and intersections, then the shape accuracy of the engagement ridge is improved, but the calculation complexity and time increase
Solution Approach 1:
The patent applies segmentation by dividing the beveling path into multiple discrete positions and calculating the grindwheel-lens intersection at each position separately. This segmented approach allows the complex calculation to be broken down into manageable steps, determining the simulated shape at each segment point and then synthesizing the overall corrected path, thereby improving accuracy while keeping the calculation process systematic and manageable.
Data Source
AI summary
A predictive calculation method for calculating the shape of a cross-section of an engagement ridge of an ophthalmic lens obtained by beveling the lens with a beveling grindwheel driven in accordance with an initial path setting. The method includes the following steps:acquiring the initial path setting for the beveling grindwheel relative to the lens;determining at least two approximations (Sii, Sij) of the shape of the cross-section under consideration of the engagement ridge, the approximations being deduced from the intersection between the beveling grindwheel and the ophthalmic lens when the beveling grindwheel is situated at two distinct positions of the initial path setting;determining the intersection between these two approximations; anddeducing therefrom the shape (Si) of the cross-section under consideration of the engagement ridge.