Donut Tooling Mold Gap Mechanism for Seamless Hollow Articles
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Solution Overview
Problem
Conventional injection molding techniques cannot produce hollow donut-shaped articles with a 360° continuous interior in a single piece, as the mold design prevents separation of the article from the interior-forming portion without cutting or creating a gap, leading to unsightly seams and vulnerability to separation and leakage when filled with liquids or gelatinous materials.
Innovation Solution
A donut tooling mold structure with a mechanism to automatically open a gap in the interior-forming member during the molding process, allowing the article to be removed without additional operator steps or apparatus modifications, and closing the gap for subsequent molding operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional injection molding mold is used to form hollow donut-shaped articles, then the mold can form the exterior shape, but the interior-forming portion cannot be separated from the molded article without creating seams or gaps
Solution Approach 1:
The mold is divided into two separate portions: an exterior-forming portion and an interior-forming portion. The interior-forming portion is further segmented to include a gap that allows for separation. This segmentation enables the molded article to be removed from the mold without creating seams, while maintaining the continuity of the hollow interior shape.
Solution Approach 2:
The interior-forming portion is extracted or removed from the molded article during the ejection process. The gap in the interior-forming portion allows it to be taken out cleanly without leaving seams or requiring additional joining operations, solving the separation problem while maintaining interior continuity.
2Ease of manufacture
If the mold is designed with a gap to allow separation, then the article can be removed without seams, but the hollow interior cannot extend 360° continuously
Solution Approach 1:
The gap in the interior-forming portion is designed to be dynamic rather than static. During the molding process, the gap is closed to allow formation of the continuous 360° hollow interior. During ejection, the gap opens to allow separation of the article from the mold. This dynamic behavior resolves the contradiction between maintaining interior continuity and enabling mold separation.
Solution Approach 2:
The gap undergoes periodic opening and closing actions corresponding to different stages of the molding cycle. The gap closes during injection to form the continuous interior, then opens during ejection to allow removal. This periodic action enables both continuous interior formation and clean separation.
3Ease of manufacture
If hollow donut-shaped articles are manufactured by separately molding two halves and joining them, then separation from the mold is possible, but the article develops unsightly seams and vulnerability to leakage
Solution Approach 1:
Rather than segmenting the final article into two halves that require joining, the mold itself is segmented into exterior-forming and interior-forming portions. This allows the article to be molded as a single seamless piece, eliminating the need for joining operations and the associated seams and leakage vulnerabilities.
Solution Approach 2:
The interior-forming portion is extracted from the molded article during ejection through the designed gap, allowing complete removal without leaving seams. This extraction method produces a seamless article with intact hollow interior, eliminating leakage paths that would result from joining separate halves.
4Device complexity
If conventional injection molding is used without gap opening mechanism, then the molding process is simple, but additional operator steps and apparatus modifications are required for article removal
Solution Approach 1:
The mold is designed to automatically open the gap and eject the molded article without requiring additional operator intervention or complex apparatus modifications. The gap mechanism is integrated into the basic mold structure, allowing the mold to serve itself in the ejection process while maintaining overall simplicity.
Data Source
AI summary
An injection molding apparatus for generally toroidal or donut-shaped articles having a hollow interior includes a hollow-interior forming member that is positioned within the mold cavity during injection to form the hollow interior of the article, and that is moved away from the mold cavity to allow removal of the molded article when the injection molding apparatus is opened following molding. The hollow-interior forming member includes an open section or gap that is closed by a gap-filling member when the injection molding apparatus is closed. When the injection molding apparatus is opened following molding, the gap-filling member vacates the open section or gap to enable the molded article to be manually separated from the annular member.