Helical Ejection Ribs for Injection Molded Article Integrity
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Solution Overview
Problem
Molded articles, particularly those with thin-walled or complex geometries, often experience undesirable deformation during ejection due to insufficient cooling and require extended cooling times or complex ejection systems to minimize defects.
Innovation Solution
Incorporation of ejection-assist features, such as helical ejection-assist ribs and retaining features, in the mold core design to facilitate controlled ejection by exerting axial forces that counteract inward deflection and deformation during demolding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ejection methods are used for thin-walled molded articles, then the ejection process is simple, but the articles experience undesirable deformation and deflection during ejection
Solution Approach 1:
The ejection system is segmented into multiple independent ejection-assist features (multiple ribs with helical slide surfaces) distributed around the mold core. Each rib provides localized ejection assistance to specific regions of the thin-walled article, allowing controlled ejection without requiring a complex overall ejection mechanism. This segmentation enables precise control over ejection forces at different locations.
Solution Approach 2:
The invention introduces a helical dimension to the ejection-assist ribs, creating helical slide surfaces that engage with corresponding helical features on the article. This helical geometry converts axial ejection motion into a controlled rotational-ejection path, providing gradual separation between the article and mold core while maintaining article integrity throughout the ejection process.
2Manufacturing precision
If extended cooling times are used to prevent deformation, then article integrity is maintained, but production time increases
Solution Approach 1:
The ejection-assist ribs are pre-configured in the mold core with helical slide surfaces positioned to engage specific regions of the thin-walled article. This preliminary arrangement ensures that as soon as ejection begins, the controlled helical separation path is immediately activated, preventing deformation without requiring extended cooling periods. The structure is prepared in advance to provide instantaneous ejection assistance.
Solution Approach 2:
The helical slide surfaces on the ejection-assist ribs act as intermediary elements between the mold core and the thin-walled article. During ejection, these intermediary helical surfaces provide a controlled interface that gradually separates the article from the mold core, distributing ejection forces evenly and preventing sudden deformation that would otherwise require longer cooling times to prevent.
3Productivity
If simple ejection systems are used, then device complexity is low, but ejection defects occur due to insufficient control over ejection forces
Solution Approach 1:
The mold core incorporates ejection-assist ribs with helical slide surfaces at specific localized positions where thin-walled sections are most susceptible to deformation. Each rib is strategically positioned to provide ejection assistance exactly where needed, rather than using a uniform complex ejection system throughout. This localized approach provides precise ejection control at critical areas while keeping the overall mold structure relatively simple.
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
Reduces ejection defects and cooling time requirements by ensuring controlled ejection, thereby maintaining article integrity and reducing production costs.
Implementation Method 1
the rib mold feature of the mold core bears against the helical slide surface of the ejection-assist rib to urge the article second portion axially away from the mold core during ejection
Data Source
AI summary
A mold core for forming an injection molded article includes a first mold surface having a thread mold extending helically about a core axis for forming internal threading in a first portion of the molded article; and a second mold surface spaced radially apart from the first mold surface for forming a second portion spaced radially apart from the first portion and connected to the first portion by a connection portion. The second mold surface includes at least one rib mold feature for forming at least one ejection-assist rib of the second portion, the ejection-assist rib having a helical slide surface extending helically about the article axis. During an initial unscrewing rotation of the molded article relative to the mold core, the rib mold feature bears against the helical slide surface to urge the second portion axially away from the mold core during ejection of the molded article.