Self-Punching Functional Element With Undercut Locking in Sheet Metal
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Solution Overview
Problem
High-strength sheet metal parts, particularly those made of high-strength steel, are difficult to weld and require significant tooling effort for press hardening, necessitating a secure and stable connection method that is efficient across varying workpiece thicknesses.
Innovation Solution
A self-punching functional element with a functional section and a fastening section featuring a punching edge and projection, which punches out a slug from the workpiece and forms undercuts for secure engagement, eliminating the need for pre-punching and allowing for easy attachment without complex welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welding is used to create connections between functional element and high-strength sheet metal part, then connection strength is improved, but manufacturing complexity and difficulty increase
Solution Approach 1:
The patent replaces the welding process (thermal/chemical joining) with a mechanical self-punching and press-fit system. The functional element includes a punching edge that mechanically punches through the workpiece and forms an undercut, creating a mechanical interlock without requiring welding operations.
Solution Approach 2:
The functional element performs the punching operation itself during the pressing-in process. The punching edge automatically punches through the workpiece material as the element is pressed in, eliminating the need for separate pre-punching or drilling operations that would be required for welding applications.
2Reliability
If press hardening with functional element insertion is used, then connection reliability is improved, but device complexity and tooling requirements increase
Solution Approach 1:
The patent extracts the punching function from complex tooling systems and integrates it directly into the functional element itself. The punching edge is built into the functional element, eliminating the need for separate punching tools or complex press hardening tooling arrangements.
Solution Approach 2:
The functional element serves multiple functions: it acts as both the fastening element and the punching tool. The same element that provides the mechanical connection also creates the hole and forms the undercut, eliminating the need for separate punching and fastening operations.
3Stability of the object's composition
If traditional rivet elements deforming the functional element are used, then connection stability is improved, but ease of operation deteriorates due to intentional deformation requirements
Solution Approach 1:
Instead of deforming the functional element to create the connection (as in traditional riveting), the patent inverts the approach by having the functional element deform the workpiece material. The punching edge punches through and deforms the workpiece to create an undercut that retains the functional element.
4Manufacturing precision
If pre-punching of workpiece is performed before functional element attachment, then manufacturing precision is improved, but productivity deteriorates due to additional process steps
Solution Approach 1:
The patent merges the punching operation and the fastening operation into a single integrated process. The functional element with the punching edge performs both hole creation and self-installation in one pressing motion, eliminating the need for separate pre-punching and fastening steps.
Solution Approach 2:
The punching edge is pre-configured on the functional element before installation. This preliminary configuration allows the element to perform the punching action automatically during the pressing-in process, eliminating the need for prior hole preparation while maintaining precise positioning.
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 enables a secure and stable connection with reduced effort, accommodating different workpiece thicknesses and preventing rotation or twisting, thus simplifying the attachment process for high-strength sheet metal parts.
Implementation Method 1
the functional element is provided with a punching edge, pre-drilling the workpiece is unnecessary. When the functional element is pressed into the workpiece, a slug is punched out of the workpiece by means of the punching edge
Implementation Method 2
The projection creates an undercut acting in the axial direction, so that the functional element is securely held in the workpiece
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
A self-punching functional element serves for fastening to a workpiece, in particular to a high-strength sheet metal part, and comprises a functional section and a fastening section, which has a contact surface for engaging a setting device, an end face facing away from the contact surface, and an outer circumferential surface connecting the contact surface and the end face. The end face is bounded radially on the outside by a punching edge for punching a slug from the workpiece, and at least one projection is provided on the outer circumferential surface adjacent to the contact surface, which rises from the outer circumferential surface in the radial direction and extends further outwards in the radial direction than the punching edge.