Molded Plastic Optical Lens with Segmented Die and Gas Pressure Control
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Solution Overview
Problem
Conventional methods for shaping plastic articles with complex uneven thickness shapes face issues such as internal stress, sticking to metal dies, separation failure, shape deformation, and birefringence due to uneven cooling and shrinkage, which affect precision and quality, especially in optical elements like lenses for laser printers and video cameras.
Innovation Solution
A method involving a metal die with a cavity defined by blocks, where a movable block and a gas supply route are used to control resin pressure and expansion, forming incomplete transfer faces with convex and concave shapes to manage shrinkage and internal stress, thereby enhancing precision and reducing birefringence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional injection molding is used to form plastic articles with complex uneven thickness shapes, then mass production cost-effectiveness is achieved, but internal stress causes sticking to metal dies, separation failure, shape deformation, and birefringence
Solution Approach 1:
The metal die is divided into multiple blocks (first block, second block, third block) that can be independently controlled. This segmentation allows different regions of the die to apply different pressures and temperatures during molding, enabling precise control over complex uneven thickness shapes while reducing internal stress and preventing sticking and deformation.
Solution Approach 2:
The invention introduces a movable block that can change position during the molding process. This dynamic adjustment capability allows the die to adapt to the shrinking and deformation of plastic articles with complex uneven thickness shapes, maintaining optimal contact pressure throughout the cooling process and preventing both sticking and separation failure.
2Manufacturing precision
If high pressure is applied during injection molding to maintain constant uniform pressure and temperature, then shape precision is improved, but shrinkage and internal stress increase causing sticking and deformation
Solution Approach 1:
Different blocks of the metal die are assigned different functions with respect to pressure application. The first block maintains high pressure for shape precision, while the second block with gas supply route controls local pressure to reduce shrinkage, and the third block provides release function. This local differentiation allows simultaneous achievement of high shape precision and reduced internal stress.
Solution Approach 2:
A gas supply route is introduced to supply compressed gas to specific regions of the mold cavity. This pneumatic control allows precise adjustment of local pressure during molding, enabling reduction of shrinkage and internal stress in critical areas while maintaining overall shape precision through differential pressure control.
3Ease of manufacture
If the metal die structure is simplified for ease of manufacture, then manufacturing cost is reduced, but control over resin pressure and shrinkage is insufficient leading to quality issues
Solution Approach 1:
The metal die is segmented into multiple independent blocks that can be manufactured separately using conventional techniques, then assembled. This segmentation maintains ease of manufacture for each individual block while enabling complex overall functionality through the combination of blocks with different functions (molding, gas supply, movable release).
Solution Approach 2:
Compressed gas is introduced as an intermediary medium through the gas supply route to control shrinkage and pressure distribution. This intermediary approach allows precise control of resin behavior without requiring complex mechanical adjustments to the die structure itself, maintaining manufacturing simplicity while achieving high quality results.
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 effectively suppresses shrinkage spread to transfer faces, enhances shape precision, and reduces internal strain, resulting in high-quality plastic articles with minimized birefringence for optical applications.
Implementation Method 1
a second block having a gas supply route; supplying compressed gas through the gas supply route to the cavity
Implementation Method 2
the movable block being slidably movable with respect to the cavity; slidably moving the movable block in a separation direction away from the cavity
Implementation Method 3
cooling and solidifying the melted resin in the cavity of metal die
Implementation Method 4
The process of shaping the plastic article includes cooling and solidifying the melted resin in the cavity of metal die
Implementation Method 5
forming incomplete transfer faces with convex and concave shapes to manage shrinkage and internal stress
Data Source
AI summary
A plastic article is formable by using a metal die having a cavity to accommodate melted resin therein at a given pressure. The plastic article includes a transfer face to which is transferred a face shape of the metal die, a projection disposed at least one face other than the transfer face, an incomplete transfer face having a concave shape disposed at the same face on which the projection is disposed, formed by an incomplete transfer of a face shape of the cavity of the metal die, and an incomplete transfer face having a convex shape disposed at least one face other than the transfer face.