Hinge Cap Undercut Segmentation for Mold Release Stability
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Solution Overview
Problem
Conventional hinge caps face challenges in maintaining the stability of the engaging portion with an undercut feature during mold release in injection molding, leading to potential damage and instability in the closed state.
Innovation Solution
The hinge cap design incorporates a configuration where multiple convex and concave portions are arranged side by side in a straight line on the outer wall portion, dispersing the mold release resistance and stabilizing the engaging state between the claw portion and the engaging portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single undercut portion is used in the engaging portion, then the mold release resistance is concentrated on that portion, but the undercut portion is easily damaged during mold release
Solution Approach 1:
The single undercut portion is divided into multiple convex portions arranged side by side in the axial direction. Each convex portion acts as a separate undercut feature, distributing the mold release resistance across multiple points rather than concentrating it on one vulnerable location. This segmentation prevents damage to any single undercut portion while maintaining the overall engaging function.
Solution Approach 2:
Multiple convex portions are strategically arranged in different locations along the axial direction, with each portion having specific local characteristics. The first convex portion engages with the claw portion while the second convex portion provides additional engagement, creating localized quality variations that optimize both mold release and closing stability.
2Reliability
If multiple convex portions are arranged side by side in the axial direction, then the mold release resistance is dispersed, but the complexity of the outer wall portion increases
Solution Approach 1:
The engaging portion is segmented into multiple convex portions that are arranged side by side in the axial direction rather than using a single complex undercut portion. This segmentation simplifies the overall structure by using multiple simple convex features instead of one complex curved surface, making the mold release process easier while maintaining engagement stability.
Solution Approach 2:
Instead of creating a complex concave undercut portion that is difficult to mold and release, the design inverts the approach by using multiple convex portions that protrude from the inner surface. This inversion makes the mold release process simpler as the convex portions can be easily released from the mold without requiring complex release mechanisms.
3Ease of manufacture
If the convex portions are arranged in a row, then the mold release resistance is dispersed along the axial direction, but the opening and closing operation becomes more complex
Solution Approach 1:
The convex portions are segmented and arranged in a row along the axial direction, with the first convex portion positioned closer to the open end and the second convex portion positioned closer to the closed end. This segmentation allows the lid to engage and disengage from each portion sequentially during opening and closing operations, simplifying the overall operation while maintaining manufacturing ease.
Solution Approach 2:
The first convex portion is positioned to engage with the claw portion during the closing operation before the second convex portion engages. This preliminary action ensures that the lid is securely closed by the first engagement point, and the second engagement point provides additional confirmation and stability, making the operation smoother and more reliable.
Data Source
Figure 1A
Figure 1B~1C
Figure 2~3
AI summary
A hinge cap formed by an injection-molding comprises an inner lid capable of being attached to a container body, a hinge, and an outer lid that is connected to the inner lid by the hinge to open and close the cap. The inner lid includes a claw portion. The outer lid includes a tubular outer wall portion and a plurality of convex portions as undercut portions and a plurality of concave portions. One convex portion and a concave portion adjacent to the one convex portion form an engaging portion capable of being engaged with the claw portion. An adjacent convex portion adjacent to the engaging portion and a concave portion adjacent to the adjacent convex portion form a mold pressing portion.