Hot Runner Lens Molding with Annular Secondary Runner
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Solution Overview
Problem
The existing injection molding processes for subminiature lenses face challenges with cooling time and material efficiency due to the use of conventional cylindrical runners, which hinder productivity and moldability, especially in multi-cavity molds where the runner volume is excessive compared to the lens volume.
Innovation Solution
The implementation of a hot runner structure with a primary sprue, primary runner, and secondary sprue maintained in a molten state, combined with a secondary runner of annular or polygonal shape and thin plate design, reduces material consumption and cooling time by allowing the primary sprue and runner to remain molten, while the secondary runner and gate are solidified, thereby improving flow balance and moldability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional cylindrical runner is used in subminiature lens injection molding, then the runner can maintain structural integrity, but the cooling time increases and productivity deteriorates
Solution Approach 1:
The runner system is divided into two distinct parts: a thick cylindrical hot runner portion (sprue and main runner) that maintains structural integrity, and a thin plate-shaped cold runner portion (secondary runner) that cools quickly. This segmentation allows each part to serve its specific function optimally without compromise.
Solution Approach 2:
Different regions of the runner system are given different thicknesses and thermal properties. The hot runner portion has larger diameter for strength, while the cold runner portion has reduced thickness for rapid cooling. This local differentiation of properties resolves the contradiction between structural requirements and cooling efficiency.
2Productivity
If a hot runner structure is applied to maintain sprue and runner in molten state, then material use efficiency improves and cooling time reduces, but the lens gate location becomes limited to side gate only
Solution Approach 1:
The hot runner structure is segmented to extend specifically to the secondary sprue location, allowing the gate to be positioned at the end of the secondary sprue rather than limited to side gate configurations. This enables top gate injection while maintaining hot runner benefits.
Solution Approach 2:
The hot runner configuration transitions from conventional horizontal side gate arrangement to a vertical top gate arrangement through the extended secondary sprue structure, adding dimensional flexibility to the gate location options.
3Productivity
If multi-cavity mold is used to increase production volume, then productivity improves, but the runner volume becomes excessively large compared to lens volume
Solution Approach 1:
The runner system is segmented into a common hot runner portion serving multiple cavities and individual cold runner portions for each cavity. This allows efficient material distribution to multiple lenses while minimizing excess runner material through the thin plate-shaped cold runner design.
Solution Approach 2:
The runner cross-sectional dimensions are optimized with the cold runner portion having reduced thickness compared to conventional runners, significantly decreasing the volume of material required for the delivery system while maintaining adequate flow characteristics.
4Adaptability or versatility
If a three-plate mold with pinpoint gates is used to efficiently apply hot runner, then gate location flexibility improves, but gate mark on lens surface occurs which is not allowed
Solution Approach 1:
The gate marking problem is eliminated by extracting the gate from the lens surface location and positioning it at the end of the extended secondary sprue, where the gate mark does not affect the optical surface quality. The hot runner structure is reconfigured to accommodate this extracted gate position.
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 shortens the cooling time for the runner, reduces material consumption, and enhances productivity by maintaining the primary sprue and runner in a molten state, improving flow characteristics and moldability, and allowing for more efficient lens production with fewer nozzles and reduced flow resistance.
Implementation Method 1
a hot runner structure with a primary sprue, primary runner, and secondary sprue maintained in a molten state
Implementation Method 2
a secondary runner of annular or polygonal shape and thin plate design, reduces material consumption and cooling time
Data Source
AI summary
An injection molded lens, to which the hot runner according to an embodiment of the present invention includes: a primary sprue; a primary runner which has a central portion connected to the primary sprue and an extension portion extending radially from the central portion; a secondary sprue of which one end is connected to the extension portion of the primary runner; a secondary runner which has a top thereof connected to the other end of the secondary sprue, has an annular shape and a thin plate shape, and has a plurality of protrusions formed on an outer circumference thereof; a plurality of gates which are connected to ends of the plurality of protrusions of the secondary runner; and a plurality of cavities connected to the plurality of gates.An injection molded lens, to which the hot runner according to another embodiment of the present invention includes: a primary sprue; a primary runner which has a central portion connected to the primary sprue and an extension portion extending radially from the central portion; a secondary sprue of which one end is connected to the extension portion of the primary runner; a secondary runner which has a top thereof connected to the other end of the secondary sprue, has a polygonal shape and a thin plate shape, and has a plurality of protrusions formed on an outer circumference thereof; a plurality of gates which are connected to ends of the plurality of protrusions of the secondary runner; and a plurality of cavities connected to the plurality of gates.