Ophthalmic Lens Molding Shells With Controlled Chamfer Geometry
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Solution Overview
Problem
Existing ophthalmic lens molding shells suffer from durability issues due to uncontrollable and small chamfers, leading to chip formation and increased fragility, which complicates lens disassembly and increases scrap rates.
Innovation Solution
The molding shells are designed with a flat facet and a first chamfer extending along the outer edge of the main face, along with a second chamfer between the edge face and the other main face, ensuring consistent chamfer sizes and improved durability through a specific machining and polishing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the molding shell edge is polished with a conventional polishing tool, then the surface finish is improved, but the chamfer size becomes uncontrollable and very small, generating chips that reduce durability
Solution Approach 1:
The edge geometry is segmented into three distinct features: a flat facet portion, a first chamfer portion, and a second chamfer portion. This segmentation allows each feature to be independently controlled and optimized, preventing the uncontrollable small chamfers that cause chips while maintaining surface finish quality.
Solution Approach 2:
Different regions of the molding shell edge are given different geometric properties. The flat facet provides a stable reference surface, the first chamfer (40° angle) provides durability by preventing chip formation, and the second chamfer (45° angle) facilitates lens disassembly. Each region's quality is optimized for its specific function.
2Strength
If the chamfer size is increased to improve durability and prevent chips, then the molding shell becomes more robust, but the lens disassembly process becomes more difficult
Solution Approach 1:
The chamfer function is segmented into two separate features: the first chamfer (40°) optimized for durability and chip prevention, and the second chamfer (45°) optimized for lens disassembly. This allows both durability and ease of operation to be improved simultaneously without compromise.
Solution Approach 2:
The solution moves from a single chamfer dimension to a multi-dimensional edge geometry with flat facet and two chamfer portions at different angles. This dimensional complexity enables independent optimization of durability (first chamfer) and disassembly ease (second chamfer).
3Ease of manufacture
If conventional machining and polishing processes are used, then the manufacturing process is simple, but the scrap rate increases due to uncontrollable chamfer sizes and chip formation
Solution Approach 1:
The flat facet is created as a preliminary feature during machining, establishing a stable reference surface before polishing. This preliminary action ensures that the subsequent polishing process produces consistent chamfer sizes and prevents chip formation, reducing scrap rate while maintaining process simplicity.
4Productivity
If the molding shell is used for extended periods to improve productivity, then more lenses are produced, but the shell becomes fragile and chips due to uncontrollable edge geometry
Solution Approach 1:
The edge geometry is optimized with specific features (flat facet, 40° first chamfer) that prevent chip formation and maintain structural integrity during repeated use. This local quality improvement at the edge extends the molding shell's operational lifetime, allowing extended use without fragility issues.
Data Source
AI summary
An ophthalmic lens molding shell (30) having two main faces (31, 32) and an edge face (33) surrounding the main faces, a first of said main faces being adapted to face another molding shell during the molding of the ophthalmic lens. The ophthalmic lens molding shell also comprises: ⋅—a flat facet (34) extending along an outer edge of the first main face, and ⋅—a first chamfer (36) extending along an outer edge of the flat facet, between said flat facet and said edge face.