Plastic Lens Protrusions for Outer Diameter Accuracy
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Solution Overview
Problem
Conventional methods for manufacturing large-sized plastic lenses, particularly those with diameters of 50 mm or more, face challenges in maintaining accurate outer diameters due to mold errors, leading to optical-axis deviations and increased costs from extensive mold modifications.
Innovation Solution
The solution involves creating a plastic lens with at least three equally spaced protrusions on its circumference, which serve as fit portions for a mirror frame, allowing for partial modification of the metal mold and precise adjustment of the lens's outer diameter through adjustable pieces in the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional injection molding is used for large-sized plastic lenses, then the lens can be manufactured with standard processes, but the outer diameter accuracy deteriorates due to mold errors and deviations
Solution Approach 1:
The invention divides the lens circumference into multiple independent adjustment regions by providing several adjustment pieces at different angular positions. Each adjustment piece can be independently modified to correct local outer diameter deviations, rather than requiring modification of the entire mold or lens circumference. This segmentation allows targeted correction of specific deviation points while maintaining standard manufacturing processes for the overall lens.
2Manufacturing precision
If the entire metal mold is modified to correct lens outer diameter deviation, then the lens accuracy improves, but the manufacturing complexity and cost increase significantly
Solution Approach 1:
The metal mold is segmented into multiple independent adjustment pieces positioned at different angular locations around the lens circumference. Each adjustment piece can be individually modified or replaced to correct local outer diameter deviations. This eliminates the need to modify the entire mold structure, significantly reducing the complexity and cost of mold modifications while achieving the required lens accuracy.
Solution Approach 2:
Instead of uniformly modifying the entire metal mold, the invention applies local quality by providing adjustment pieces only at specific angular positions where outer diameter deviations occur. Each adjustment piece is tailored to correct the local deviation at its specific position, allowing precise correction of lens outer diameter without unnecessary modifications to other parts of the mold.
3Manufacturing precision
If the lens outer diameter is adjusted by modifying the entire mold circumference, then the optical axis alignment improves, but the production time and cost increase due to extensive rework
Solution Approach 1:
The adjustment mechanism is segmented into multiple independent adjustment pieces that can be individually modified or replaced. When optical axis alignment requires correction, only the specific adjustment pieces at affected angular positions need to be modified, not the entire mold. This dramatically reduces production time and maintains high productivity while achieving the required optical axis alignment accuracy.
Solution Approach 2:
The adjustment pieces are designed to be pre-positioned at specific angular locations during mold assembly. This preliminary positioning allows for quick identification and modification of only those pieces that require adjustment, eliminating the need for extensive inspection and modification of the entire mold circumference. The preliminary arrangement of adjustment pieces streamlines the correction process and maintains production efficiency.
Data Source
AI summary
A plastic lens, which does not require a modification to an inner diameter of a mirror frame but is uniform in outer diameter, is provided and include: protrusions on the circumference in at least three points divided thereof into three equal parts except for an injection gate point, in positions equally distant to a center O of the plastic lens. The protrusions have respective outer surfaces provided as fit portions to a mirror frame. The plastic lens preferably has a diameter of 50 mm or more and a thickness smallest at the center thereof.