Perimeter Gate Mold Design for Bubble-Free Urethane Molding
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Solution Overview
Problem
Existing molds face challenges in preventing bubble inclusion and underfilling during the injection of urethane raw materials, especially in complex shapes, and struggle with separating solidified material portions from molded articles, leading to inconsistent quality and difficulty in removing solidified material from the gate.
Innovation Solution
A mold design where the molding material is injected through an inlet positioned higher than the cavity top, filling the cavity from the bottom through a gate at the bottom, with a vent at the top to evacuate air, and a gate that communicates with the perimeter to minimize dead ends and facilitate separation by creating stress concentrations upon curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the gate is arranged at or near the bottom of the cavity and the vent at or near the top, then large bubbles are prevented from being included, but small bubbles formed during feeding still occur in some cases
Solution Approach 1:
The patent inverts the conventional gating approach by positioning the gate at the top of the cavity rather than at the bottom, and positioning the vent at the bottom rather than at the top. This inversion allows molding material to feed downward from the top gate, preventing both large and small bubbles from being trapped during the filling process, while the bottom vent effectively evacuates air and bubbles generated during feeding.
2Object-affected harmful factors
If the inlet is arranged at a position higher than the top of the cavity, then bubble inclusion is prevented, but dead-ends are formed causing bubble inclusion
Solution Approach 1:
The patent extracts and eliminates dead-end portions from the cavity design by ensuring the cavity has no dead ends where molding material can stagnate. The cavity is designed with continuous flow paths that allow molding material to fill uniformly from the top gate without creating stagnant zones, while the bottom vent prevents bubble accumulation.
3Manufacturing precision
If the gate is narrower than the runner to uniformly feed raw material, then bubble inclusion and underfilling are prevented, but the mold is insufficient for uniform injection in complex shapes
Solution Approach 1:
The patent applies local quality by having the gate communicate with the perimeter of the cavity rather than being a single narrow point. This allows different regions of the cavity to receive molding material through the peripheral gate connection, ensuring uniform filling and preventing underfilling in complex shapes while maintaining control over bubble formation.
4Ease of operation
If the gate communicates with the perimeter of the cavity, then dead ends are minimized and separation is facilitated, but the structure complexity increases
Solution Approach 1:
The patent uses the gate as an intermediary structure that communicates with the cavity perimeter through a connecting portion. This connecting portion acts as a mediator that facilitates both uniform material distribution and easy separation of solidified gate material from the molded article, while the overall structure remains integrated and manageable.
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 bubble-free filling, prevents bubble inclusion, and allows for easy separation of solidified material from the molded article, ensuring uniform quality and reducing the formation of bubbles and voids, even in complex geometries.
Implementation Method 1
the molding material is fed into the cavity through the gate arranged at the bottom of the cavity. The cavity is filled with the molding material
Implementation Method 2
the molding material is fed into the vent communicating with the cavity at the top of the cavity and serving as a space configured to partially discharge the molding material from the cavity
Implementation Method 3
the feeding rate of the molding material into the cavity is sufficiently low to generate a laminar flow
Implementation Method 4
a self-curable molding material is fed into the mold. When the flowable self-curable molding material is fed into the inlet
Data Source
AI summary
A mold 10 includes a gate 27 communicating with the entire perimeter of a cavity 28 serving as a space configured to form a molded article 60. A self-curable molding material with flowability is fed into the perimeter of the cavity 28 through the gate 27; hence, the mold 10 has a small number of dead ends compared with the case where, for example, the molding material is fed into the cavity 28 through a part of the cavity 28, preventing the formation of bubbles left in the cavity 28. The arrangement of a gate 27 and a bent 35 each making an acute angle results in the spontaneous separation of the molded article in the cavity 28 from solidified material portions in the gate 27 and the vent 35 due to shrinkage on curing.