Plastic Molded Article Ribs Disperse Shrinkage Force
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Solution Overview
Problem
Plastic molded articles with integrally molded tubular portions often suffer from molding shrinkage, leading to dimensional inaccuracies and displacement of embedded components, such as nuts, which can prevent proper assembly of bolts and other fixtures.
Innovation Solution
Incorporating pairs of ribs that connect the outer circumferential surfaces of the first and second tubular portions, with the ribs located on opposite sides of an imaginary plane including the central axes of both tubular portions, to disperse the pulling force caused by molding shrinkage and maintain the dimensional accuracy of the second tubular portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the base, first tubular portion, and second tubular portion are integrally molded of plastic, then manufacturing efficiency is improved, but molding shrinkage causes the second tubular portion to displace from its proper position
Solution Approach 1:
The invention introduces ribs that segment the continuous plastic mass into distinct structural zones. The ribs divide the region between the first and second tubular portions into multiple sections, which prevents uniform shrinkage contraction and maintains the positional integrity of the second tubular portion during molding.
Solution Approach 2:
The ribs are strategically positioned to create localized structural reinforcement zones. By adding material specifically at the locations where shrinkage distortion is most likely to occur (between the tubular portions), the invention provides targeted resistance to shrinkage forces without affecting the overall molding process.
2Adaptability or versatility
If the inner diameter of the first tubular portion is larger than the second tubular portion, then functional requirements are met, but the second tubular portion is pulled toward the first due to molding shrinkage
Solution Approach 1:
The ribs act as counteracting structural elements that oppose the shrinkage force. By adding material mass in the form of ribs between the tubular portions, the invention creates a counterbalancing structure that resists the pulling force generated by differential shrinkage of the first and second tubular portions.
Solution Approach 2:
The invention addresses the shrinkage problem by adding a third dimension (vertical height of ribs) to the structural configuration. Instead of merely adjusting the radial dimensions of the tubular portions, the ribs extend vertically to provide additional structural support and resistance to shrinkage forces in a different dimensional plane.
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 configuration effectively prevents the second tubular portion from collapsing towards the first, ensuring accurate dimensional stability and allowing for proper fastening of bolts and other components, while maintaining the size and stiffness of the molded article.
Implementation Method 1
When such a plastic cylinder head cover is molded, molding shrinkage occurs. In the case of the cylinder head cover of the above-described publication, the plug cylinder and the receiving portion shrink toward the respective central axes.
Data Source
AI summary
A plastic molded article includes a base having a main surface, a first tubular portion protruding from the main surface, a second tubular portion protruding from the main surface and having an inner diameter smaller than that of the first tubular portion, and a pair of ribs that protrudes from the main surface and connects an outer circumferential surface of the first tubular portion and an outer circumferential surface of the second tubular portion to each other. The base, the first tubular portion, the second tubular portion, and the ribs are integrally molded of plastic. The ribs are located on opposite sides of an imaginary plane that includes a central axis of the first tubular portion and a central axis of the second tubular portion.