Optical Tool Polishing for Uniform Flow Fronts
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Solution Overview
Problem
Conventional contact lens molding processes result in non-uniform flow fronts due to differential friction on tool surfaces, leading to cylindrical distortion and warpage in lenses, as only the front tool is typically polished, while the back tool is not.
Innovation Solution
Polishing both sides of the optical tools, including the non-contacting surfaces, to reduce boundary layer effects and achieve a more uniform flow front, using methods such as diamond compound paste, polishing pads, and magnetic resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If only the front tool is polished while the back tool is left unpolished, then the manufacturing process is simpler and faster, but cylindrical distortion and non-uniform flow fronts occur in the lenses
Solution Approach 1:
The patent applies polishing treatment specifically to the portions of the tools that contact the prepolymers during molding. This includes the front surface of the front tool and the back surface of the back tool, while leaving other portions of the tools unpolished. This selective application of polishing achieves uniform flow fronts and eliminates cylindrical distortion without requiring complete polishing of all tool surfaces, thus resolving the contradiction between manufacturing precision and device complexity
2Manufacturing precision
If both front and back tools are fully polished, then uniform flow fronts and reduced cylindrical distortion are achieved, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
Instead of polishing entire tool surfaces, the invention polishes only the specific portions that contact the prepolymers during the molding process. This localized polishing approach achieves the desired uniform flow front and reduced cylindrical distortion while significantly reducing the time and effort required compared to complete tool polishing
3Productivity
If unpolished tools are used, then the manufacturing process is faster and simpler, but boundary layer effects cause non-uniform flow fronts and lens warpage
Solution Approach 1:
The invention applies polishing treatment locally to the tool portions that contact the prepolymers, maintaining a balance between manufacturing speed and lens quality. The polished contact surfaces eliminate boundary layer effects and ensure uniform flow fronts, while the overall process remains efficient by avoiding complete tool polishing
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 approach significantly reduces cylindrical distortion in contact lenses, ensuring more precise and uniform mold production, particularly beneficial for asymmetrical lenses with features like prism ballast, by maintaining a consistent flow front and minimizing radius changes.
Implementation Method 1
The tool is then lathed to more exact specifications. The two tools that are used to create the portions of the mold halves that contact the contact lens prepolymers (front tools) may then be polished to remove any lathe marks.
Implementation Method 2
polishing may be achieved by using diamond compound paste, a polishing pad, and/or magnetic resonance
Implementation Method 3
The polishing of the front tool without polishing the back tool causes the mold material to be affected by the different coefficient of friction on the top and bottom surfaces (boundary layer effects), which causes a non-uniform flow front.
Data Source
AI summary
This invention is related to the process of polishing the optically critical surface of the front piece as well as the back piece, or non-optical surface, used to make molds used in double-sided molding process to make contact lens for reducing warpage of the mold, radius changes in different cavities and amount of cylindrical distortion. The polishing of both of the front piece and back piece causes the mold material to see a very similar coefficient of friction on both top and bottom surface and provides uniform flow front.