Optical Element Compression Molding Asymmetric Protrusion
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Solution Overview
Problem
The existing manufacturing methods for optical devices face challenges in ensuring a stable flow of molten resin during injection molding due to protrusions from the optical functional part, leading to inconsistent weld lines and potential sink marks or fragments in the edge part, particularly when the preform is off-center or the compression molding conditions vary.
Innovation Solution
The method involves using a pair of molding molds with specific inclination angles to form a protrusion part during compression molding, which biases the injection molding material to ensure a stable flow path by maintaining a cross-sectional area of at least 60% on one side when divided by a perpendicular bisector, preventing flow hindrance and allowing consistent edge part formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the preform is placed off-center or compression molding conditions vary, then the outer peripheral edge of the optical functional part protrudes unevenly into the injection molding cavity, but this causes flow resistance variation and inconsistent weld line positions in the edge part
Solution Approach 1:
The invention introduces an asymmetric inclination part transfer surface with a specific inclination angle (α) that is greater than 0° and less than or equal to 15°. This asymmetric design causes the protrusion part to be biased toward one side (HS1 side), creating a larger cross-sectional area on that side. This asymmetry compensates for preform placement variations and ensures consistent weld line positioning by directing molten resin flow in a controlled manner, regardless of minor preform position deviations.
2Shape
If the outer peripheral edge of the preform protrudes from the compression molding cavity to the injection molding cavity, then the injection molding cavity is narrowed, but this hinders the flow path for molten resin and causes sink marks or fragments
Solution Approach 1:
The invention applies local quality by creating a protrusion part with non-uniform cross-sectional area through the inclination part transfer surface. The cross-sectional area varies along the optical axis direction, with a larger area on the HS1 side and a smaller area on the HS2 side. This localized geometric variation guides molten resin flow around the protrusion part, preventing flow hindrance and eliminating sink marks or fragments by ensuring adequate resin distribution.
3Volume of moving object
If the inclination part transfer surface has a small inclination angle, then the protrusion part cross-sectional area is reduced, but this increases flow resistance and causes welding line position variation
Solution Approach 1:
The invention optimizes the inclination angle (α) parameter of the inclination part transfer surface, setting it within the specific range of greater than 0° and less than or equal to 15°. This parameter optimization balances the cross-sectional area of the protrusion part with the flow characteristics of molten resin. The optimized angle ensures adequate resin flow while maintaining consistent welding line position, preventing both flow resistance issues and position variation.
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 ensures the production of high-quality optical devices with stable edge parts and consistent weld lines, reducing the occurrence of defects and enhancing manufacturing efficiency by maintaining a stable flow path for the injection molding material.
Implementation Method 1
a compression molding step of filling the optical functional part transfer surface of one mold of the pair of molding molds with a compression molding material having a smaller volume than the volume of the optical device, expanding the compression molding material while the molding molds being closed to transfer the shapes of the optical functional part transfer surfaces and the connecting part transfer surfaces of the molding molds to the compression molding material
Implementation Method 2
an injection molding step of filling the edge part molding cavity with a molten injection molding material in a state where the pair of molding molds are closed, and forming an injection-molded part at an outer periphery of the compression-molded compression molding material
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
Provided is a high-quality optical devices stably produced without the flow of molten resin within an injection molding cavity being hindered by the protrusion of an outer peripheral edge of a lens after compression molding. A cavity formed when a pair of molding molds are closed has an optical functional part molding cavity 27; an annular connecting part molding cavity 28 connected to an outer peripheral edge of the optical functional part molding cavity; and an edge part molding cavity 29 connected to an outer peripheral edge of the connecting part molding cavity.