Surface Fastener Stem Geometry for Microsized Pawl Molding
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Solution Overview
Problem
Existing manufacturing methods for surface fasteners face challenges in forming microsized pawl portions on engaging elements due to difficulties in filling cavities with molten resin, leading to reduced flexibility and increased risk of tear strength in the cross direction, especially when using twin-roll molding devices, and stretching processes can cause breakage in the machining direction.
Innovation Solution
A surface fastener design with stem portions having different shapes in the machining and cross directions, featuring a straight or substantially straight outer surface in one direction and a curved surface in the other, along with a staggered arrangement of engaging elements and through-holes in the molding device, to enhance peel strength and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a twin-roll molding device is used to manufacture surface fasteners, then the base part can be made thinner and flexibility improved, but it becomes more difficult to fill the cavities with molten synthetic resin, preventing stable formation of microsized pawl portions
Solution Approach 1:
The engaging elements are designed with segmented structures including stem portions and engaging heads with microsized pawl portions. The segmentation allows the molten resin to fill cavities more effectively while maintaining the thin base part design, as each segment can be formed independently through the staggered through-hole arrangement.
Solution Approach 2:
The stem portions are designed with asymmetric shapes where the outer surfaces facing the cross direction are curved while those facing the machining direction are straight. This asymmetry optimizes the cavity filling process in the twin-roll molding device, enabling stable formation of microsized pawl portions while maintaining thin base part thickness.
2Strength
If the outer surfaces of stem portions are made straight in the cross direction, then peel strength in the cross direction is enhanced, but manufacturing complexity increases due to different shape requirements in different directions
Solution Approach 1:
The stem portions exhibit local quality variations where outer surfaces facing the cross direction are curved to enhance peel strength, while outer surfaces facing the machining direction are straight for easy manufacturing. This localized differentiation allows optimization of specific properties in specific directions without uniformly increasing overall manufacturing complexity.
Solution Approach 2:
The invention addresses the shape requirement by considering three-dimensional geometry rather than two-dimensional constraints. The stem portions are designed with different surface characteristics in different spatial directions (curved in cross direction, straight in machining direction), allowing peel strength enhancement without proportionally increasing device complexity through volumetric optimization.
3Strength
If through-holes in the molding device are arranged in a staggered pattern, then engaging elements can be formed with improved peel strength and flexibility, but the molding device structure becomes more complex
Solution Approach 1:
The molding device uses segmented through-holes arranged in a staggered pattern rather than a uniform grid. This segmentation allows the device to form engaging elements with improved peel strength and flexibility characteristics while distributing the structural complexity across multiple simple, repeating components rather than requiring a single complex structure.
Data Source
AI summary
A surface fastener includes a base part and a plurality of engaging elements formed integrally with the base part. A lower half part of the stem portion has a first shape in which an outer surface is formed straightly or substantially straightly on viewing the engagement element from the machining direction, and the lower half part has a second shape including a part where an outer surface is curved toward the surface of the base part on viewing engagement element from the cross direction. Thus, the surface fastener has a structure and/or characteristic that is different between the machining direction and the cross direction.