Clinch Pin Fastener Integrated Undercut Forging
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Solution Overview
Problem
Clinch-type fasteners require a secondary operation to form the undercut, which increases costs and complexity, especially for small diameters where tight tolerances are necessary.
Innovation Solution
The clinch pin is forged with an integrated undercut, tapered point, and tangential interference band during the same operation, eliminating the need for a secondary step and ensuring precise fit without additional stress on the plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the undercut is formed in a secondary operation after forging, then the fastener can be manufactured with standard forging processes, but the manufacturing cost increases and production time is extended
Solution Approach 1:
The patent combines the formation of the undercut with the initial forging operation by designing a multi-component die system. The die assembly includes a first die for forming the head and displacer, and a second die with a cavity that forms the undercut simultaneously during the same forging stroke, eliminating the need for a separate secondary operation.
2Device complexity
If the undercut is formed in a secondary operation, then the forging process remains simple, but additional cleaning operations are required increasing complexity
Solution Approach 1:
The patent integrates undercut formation into the forging process using a specially designed die assembly. The second die cavity is configured to form the undercut directly during forging, eliminating subsequent cleaning operations and reducing overall manufacturing complexity despite the more complex die design.
3Manufacturing precision
If tight tolerances are applied to small diameter fasteners, then the interference fit precision is improved, but the manufacturing difficulty and cost increase
Solution Approach 1:
The patent achieves precise interference fits for small diameter fasteners by forming all critical features (head, displacer, undercut) in a single integrated forging operation. The simultaneous formation ensures consistent dimensional relationships and reduces cumulative tolerance buildup that would occur with multi-step processes.
Solution Approach 2:
The patent optimizes the forging parameters including die cavity dimensions, compression ratio, and material flow characteristics to achieve the required tight tolerances for small diameter fasteners. The die design incorporates specific geometric parameters that control material distribution and feature formation to meet precision requirements.
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 method allows for the formation of a clinch pin with all necessary features in a single operation, achieving a precise interference fit with minimal stress on the plate, suitable for small diameters, and eliminating tolerance issues.
Implementation Method 1
The blank is compressed end-to-end between a top die and a bottom die whereby the axial compression of the blank causes the outward bulging of the shank at its midline
Implementation Method 2
The method of forming the above-described fastener comprises cold-forging a fastener blank having a head, a shoulder and a shank of reduced diameter
Data Source
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AI summary
A clinch-type fastener is formed by simultaneously creating an undercut during the same forging that creates the head and displacer of the fastener. A fastener blank is compressed end- to-end between top and bottom dies whereby the axial compression of a blank causes the outward bulging of the shank at its midline. Simultaneously, a tapered end point and a tangential interference band are formed provided by a curvilinear-shaped bulge in the shank. As the bulge is formed an undercut is created between the bulge and a shoulder which extends downwardly from a head of the fastener. This method of formation and the fastener produced thereby are particularly suited to the manufacture of small clinch pins having a diameter in the range of 1.0 mm.