3D Printed Wafer Injection Molding for Optical Lenses
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Solution Overview
Problem
Fused Deposition Modeling (FDM) 3D printing fails to produce parts of optical quality and mechanical strength suitable for ophthalmic lenses due to surface roughness and poor inter-strand adhesion, making it unsuitable for injection over-molding with functional wafers.
Innovation Solution
Selecting a wafer material with a glass transition temperature between 100° C. below and 15° C. below the base lens material's Tg ensures viscoelastic deformation during injection molding, reducing surface roughness and enhancing inter-strand adhesion by matching the Tg of the wafer to the base lens material within specific temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If FDM 3D printing is used to manufacture wafers, then manufacturing flexibility and customization are improved, but optical quality deteriorates due to surface roughness and light scattering
Solution Approach 1:
The manufacturing process is divided into two independent stages: (1) FDM 3D printing to create the functional wafer with customized functionality, and (2) injection over-molding to create the base lens. This segmentation allows each process to be optimized independently - the FDM process can focus on manufacturing flexibility while the injection molding process ensures optical quality
Solution Approach 2:
The functional wafer acts as an intermediary component between the manufacturing process and the final lens product. By creating the wafer separately through FDM printing and then bonding it to the injection-molded base lens, the patent enables customization of optical properties without compromising the overall lens quality
2Ease of manufacture
If FDM 3D printing is used to manufacture wafers, then ease of manufacture is improved, but mechanical strength deteriorates due to poor inter-strand adhesion
Solution Approach 1:
The patent controls the glass transition temperature (Tg) of the wafer material relative to the base lens material. By selecting a wafer material with Tg within a specific range (at or between about 100°C below to at or about 15°C below the base lens material Tg), the material properties are optimized to achieve both ease of manufacture and adequate mechanical strength
Solution Approach 2:
The final lens product is a composite structure consisting of the FDM-printed functional wafer bonded to the injection-molded base lens. This composite approach allows the wafer to provide customized functionality while the base lens provides structural support and mechanical strength
3Manufacturing precision
If wafer material Tg is selected at or between 100°C below to 15°C below base lens material Tg, then optical quality is improved through viscoelastic deformation, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes the viscoelastic properties of the wafer material by controlling its Tg relative to the base lens material. During injection molding, the temperature conditions cause the wafer material to undergo viscoelastic deformation, which naturally smooths the surface and improves optical quality without requiring additional post-processing steps
Solution Approach 2:
The wafer material's viscoelastic deformation during injection molding automatically performs the surface smoothing function. The material self-adjusts its properties during the molding process to achieve optical quality, eliminating the need for separate surface treatment operations
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
The process results in an optically smooth ophthalmic lens with improved mechanical strength and optical quality, as the viscoelastic deformation of the wafer material increases adhesion and reduces surface roughness, enabling the production of high-quality ophthalmic lenses.
Implementation Method 1
the wafer material softens enough to undergo viscoelastic deformation during injection molding. Wafer viscoelastic deformation reduces surface roughness of the wafer's coarse, light scattering surface. Viscoelastic deformation increases inter-diffusion of adjacently-deposited filament strand.
Implementation Method 2
filling the mold cavity with molten base lens material
Implementation Method 3
A FDM 3D printer builds parts by extruding a thermoplastic filament through a heated nozzle. The printer continuously moves the nozzle around, depositing melted material at pre-determined locations layer-by-layer.
Data Source
AI summary
Disclosed herein is an injection molding method for making optical thermoplastic lenses using 3D-printed functional wafers. The wafer and base lens are made of different materials having dissimilar glass transition temperatures.