Print Pad Shrinkage Compensation via Cavity Base
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Solution Overview
Problem
Manufacturers face challenges in producing print pads with the required precise contour and high polish needed to effectively apply colored ink to the concave surface of contact lens molds, leading to a high percentage of discarded products.
Innovation Solution
A method involving the use of a male mold with a polished surface to create a female mold through injection molding, ensuring the print pad body retains a highly polished and precise contour, achieved by filling the mold with a polymer that hardens and contracts, allowing the base to compensate for shrinkage without deforming the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a print pad is manually polished and contoured to meet high standards, then the surface polish and contour precision are improved, but the manufacturing time and labor cost increase
Solution Approach 1:
The male mold is pre-polished to a high shine before injection molding, so that the female mold and subsequent print pads inherit this polished surface without requiring manual polishing steps. This preliminary preparation of the mold ensures high surface quality is built into the manufacturing process itself.
Solution Approach 2:
The female mold is created as a precise copy of the male mold through injection molding, transferring the polished surface geometry and contour specifications directly to the print pad body. This copying process eliminates the need for manual contouring and polishing operations.
2Manufacturing precision
If a high percentage of print pads are discarded due to failing to meet standards, then the quality control is maintained, but the productivity and manufacturing efficiency decrease
Solution Approach 1:
The injection molding process creates a precise copy of the polished male mold geometry in the female mold, ensuring every print pad produced meets the high contour and polish standards. This eliminates variability and reduces defective units.
Solution Approach 2:
The manufacturing method changes from manual polishing and contouring to injection molding with pre-polished molds, fundamentally altering the process parameters to achieve consistent high-quality output with higher production efficiency.
3Ease of operation
If the print pad body is made compressible for effective ink application, then the functionality is improved, but the structural stability and manufacturing complexity increase
Solution Approach 1:
The appropriate degree of compressibility is built into the polymer material selection and mold design parameters, allowing the print pad body to deform effectively against the concave mold surface while maintaining structural integrity. The compression characteristics are engineered into the manufacturing process itself.
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 consistently produces print pads with the desired contour and polish, reducing the need for manual polishing and subsequent deformation, thereby increasing the yield of functional print pads for contact lens manufacturing.
Implementation Method 1
the mold is filled with a liquid polymer of the type that will harden to form the body of a print pad
Implementation Method 2
As the liquefied material hardens, it contracts, and as the liquid contracts, some liquid is withdrawn from the cavity in the base through the hole and into the body of the female mold
Implementation Method 3
surface tension will retain a bubble of liquefied polymer above the annular ridge surrounding the rearward opening of the female mold
Data Source
AI summary
A print pad for printing on a concave surface is molded to the forward surface of a cylindrical base. The base has a cavity therein and at least one hole extending from the forward surface thereof to the cavity. The print pad is made by filling a female mold with liquid polymer and positioning the forward surface of the base against the rear of the mold. Excess liquid polymer from the mold flows through the hole and into the cavity. As the polymer cures it contracts and draws liquefied polymer out of the cavity so that the cured print pad is not deformed.