Self-Punching Fastener Geometry for High-Strength Sheet Joining
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Solution Overview
Problem
Establishing a secure and stable connection between a functional element and a high-strength sheet metal part, particularly in the automotive industry, is challenging due to the difficulty in welding high-strength steel and the need for complex tooling and temperature control in press hardening processes.
Innovation Solution
A self-punching functional element with a punching edge and radial projection that creates an undercut upon pressing into the workpiece, eliminating the need for pre-punching and allowing secure fastening without the complexity of welding or high-strength tooling requirements, using a bolt or nut element with external or internal threads for secure engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welding connections are used to establish connections between functional element and high-strength sheet metal part, then connection strength is improved, but manufacturing complexity and difficulty increase due to difficulty in welding high-strength steel
Solution Approach 1:
The patent replaces the welding process (thermal/chemical joining) with a mechanical pressing process. The functional element is pressed into the workpiece to create a mechanical interlock through material displacement and deformation, forming undercuts that provide secure anchoring without requiring welding operations on high-strength steel.
Solution Approach 2:
The functional element performs dual functions: it serves as both the fastening component and the punching tool. The pressing edge of the functional element automatically punches the hole and creates the undercut during the pressing operation itself, eliminating the need for separate pre-punching operations and simplifying the manufacturing process.
2Reliability
If press hardening process is used to insert functional elements into workpieces, then connection reliability is improved, but device complexity increases due to very high level of tooling technology and homogeneous temperature control requirements
Solution Approach 1:
The patent replaces the complex thermal press hardening process with a simpler mechanical pressing operation. Instead of requiring homogeneous temperature control and specialized tooling for heat treatment, the functional element is directly pressed into the workpiece at ambient conditions, creating a reliable mechanical connection through material displacement and undercut formation.
Solution Approach 2:
The patent extracts the essential function of creating a secure connection from the complex press hardening process. By focusing only on the mechanical pressing and material displacement aspects while eliminating the thermal processing requirements, the solution achieves reliable connections with significantly reduced tooling complexity.
3Ease of operation
If pre-punching of workpiece is performed before inserting functional element, then insertion ease is improved, but manufacturing steps and time increase
Solution Approach 1:
The patent merges the punching operation and the fastening operation into a single integrated pressing action. The functional element with its pressing edge simultaneously creates the hole and establishes the mechanical connection in one step, eliminating the need for separate pre-punching and insertion operations.
Solution Approach 2:
The functional element serves as its own installation tool. The pressing edge of the functional element automatically performs the punching function during the pressing operation, so no separate punching tool or pre-punching step is required. The element installs itself by creating its own receiving hole and anchoring features simultaneously.
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 self-punching functional element achieves a secure hold in high-strength sheet metal parts with varying thicknesses, eliminating the need for pre-punching and complex welding, enabling efficient assembly with reduced effort and broad applicability across different workpiece thicknesses.
Implementation Method 1
the pre-punching of the workpiece is obsolete. On the pressing of the functional element into the workpiece, a slug is punched out of the workpiece by means of the punching edge
Implementation Method 2
The projection in so doing brings about an undercut acting in the axial direction such that the functional element is securely held in the workpiece
Data Source
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 that has a contact surface for an engagement of a setting device, an end face remote from the contact surface, and an outer peripheral surface connecting the contact surface and the end face. The end face is radially outwardly bounded by a punching edge for punching a slug out of the workpiece, and at least one projection is provided at the outer peripheral surface adjacent to the contact surface, said projection rising from the outer peripheral surface in a radial direction and extending further outwardly in the radial direction than the punching edge.