Rotary Clinch Fastener Tools for Low-Stress Metal Flow
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Solution Overview
Problem
Existing rotary installation tools for clinch fasteners face challenges such as the need for varied displacer shapes to fully fill the volume around the fastener, metal shearing and reshaping due to friction and sharp edges, and torsional stresses that cause cosmetic marks on the panel.
Innovation Solution
The development of a rotary press tool with multiple types of displacers, including fixed reduced area, rolling ball, full ring, and oscillating displacers, which reduce axial and torsional stresses by converting installation force to torque and minimizing friction, allowing for customizable composite metal flow shapes and incremental deformation without material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If standard rotary installation displacers are used, then installation force is reduced, but the volume around the fastener is not fully filled and cosmetic marks occur
Solution Approach 1:
The displacer is segmented into multiple zones with different profiles (e.g., tapered zone, cylindrical zone, beveled zone) that act sequentially during rotation. Each zone performs a specific function: the tapered zone initiates metal flow, the cylindrical zone continues displacement, and the beveled zone completes the filling. This segmentation allows full volume filling while maintaining low installation force and preventing cosmetic marks.
2Device complexity
If a single displacer shape is used, then device complexity is reduced, but the ability to fully fill the volume around the fastener is limited
Solution Approach 1:
The displacer is divided into multiple functional zones with different profiles along its circumference. These zones are integrated into a single displacer body, providing multiple metal flow shapes without requiring multiple separate displacers. This achieves full volume filling while maintaining relatively simple device structure.
Solution Approach 2:
Multiple displacer functions (tapered displacement, cylindrical displacement, beveled displacement) are merged into a single displacer component. The different profile zones work sequentially during one rotational cycle, combining the effects of what would otherwise require multiple separate displacers, thereby filling the entire volume around the fastener.
3Ease of manufacture
If solid displacers slide around the installation hole, then metal is sheared and reshaped, but friction causes torsional stresses and cosmetic marks
Solution Approach 1:
The displacer applies metal displacement in periodic increments during rotation rather than continuous sliding. The tool rotates in steps, allowing the displacer to engage, displace metal, then retract slightly before the next engagement. This periodic action reduces cumulative torsional stress and prevents cosmetic marks while still achieving the desired metal deformation to fill the volume around the fastener.
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
The solution effectively reduces installation forces and torsional stresses, minimizing material deformation and cosmetic damage, while enabling the use of different displacer shapes on a single tool, thereby simplifying manufacturing and improving the installation process.
Implementation Method 1
rotary press which imparts both rotation and pressing force to the workpiece to achieve attachment of the fastener to the workpiece
Implementation Method 2
Multiple displacers where the displacers roll on the surface of the metal while being pushed axially, such as ball bearings. The result is reduced friction given that the displacers are not dragging around the surface of the installation hole, but are rolling instead.
Data Source
AI summary
Tooling is held within the nose of a rotary punch and as the tool is rotated and forced against a workpiece a fastener within the tool becomes affixed to the workpiece. The tools have displacers which non-destructively deform and reshape the workpiece without any loss of workpiece material. The tools have various types of displacers including; tapered and arcuate displacers which act in concert to progressively act upon the workpiece; spherical displacers which may be fixed or rotatable such as caged ball bearings; and a full-circle displacer ring which wobbles as it presses against the workpiece. In the case of fixed spherical displacers, a multi-stroke method can be employed where the tool is rotated after each stroke in a group of installation strokes.