Self-Pierce Rivet Tip Machining for Defect Removal
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Solution Overview
Problem
Conventional methods of manufacturing self-pierce rivets often result in defects such as macroscopic cracks and irregular tip shapes, which can lead to weakness and uneven flaring, affecting the reliability and quality of the joints produced.
Innovation Solution
A method involving the separation of wire into slugs, followed by forging and subsequent machining operations on the tip or tail end of the rivets to remove defects and improve geometric consistency, ensuring a uniform tip shape and reducing the likelihood of uneven flaring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If slugs are fractured from wire to separate into individual pieces, then the wire is divided into discrete rivet components, but macroscopic cracks and defects are created that weaken the rivet structure
Solution Approach 1:
The wire is separated into discrete slugs through controlled fracturing, dividing the continuous material into individual rivet components that can be separately formed and processed
Solution Approach 2:
Defects are removed from the slug before the forging process begins, preventing defect propagation during subsequent forming operations and ensuring higher reliability in the final rivet product
2Ease of manufacture
If slugs are fractured from wire, then individual rivet components are obtained, but the slug ends have oblique surfaces causing circumferential irregularity in the rivet tip shape
Solution Approach 1:
The slug surface is machined to a precise, uniform geometry before forging, eliminating the oblique surfaces created by fracturing and ensuring consistent tip shape throughout the circumferential direction
Solution Approach 2:
The mechanical fracturing process is supplemented with a machining operation that replaces the irregular oblique surface with a precisely controlled geometry, substituting the variability of fracture with the precision of machining
3Productivity
If conventional forging is used without prior machining, then the manufacturing process is simpler and faster, but defects remain in the rivet causing potential joint failure
Solution Approach 1:
A machining operation is performed on the slug before forging to remove defects and create a uniform surface, preventing defect propagation during the subsequent forging and final rivet formation processes
Solution Approach 2:
The additional machining step, while increasing process complexity, converts the potential harm of defect propagation into a benefit by ensuring high reliability rivets that prevent joint failure, ultimately improving overall system performance
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 method enhances the quality of self-pierce rivets by reducing defects and improving tip uniformity, leading to stronger and more reliable joints with controlled flaring, thereby increasing the reliability of the manufacturing process.
Implementation Method 1
performing a machining operation on the tip the rivet or on the tail end of the slug from which the rivet was forged
Implementation Method 2
forging a plurality of rivets from the slugs, each rivet having a head formed from the head end of a slug and a tip formed from the tail end of that slug
Implementation Method 3
the material of the workpiece plastically deforms. This flow of workpiece material causes the annular tip of the rivet to flare outwards
Data Source
AI summary
A method of manufacturing self-pierce rivets from a length of wire comprises separating the length of wire to form a plurality of slugs, each slug defining a head end and a tail end. The method further comprises forging a plurality of rivets from the slugs, each rivet having a head formed from the head end of a slug and a tip formed from the tail end of that slug, the head and the tip of the rivet being separated by a shank which defines a longitudinal axis, the rivet having a bore which runs substantially longitudinally through the tip and at least part way along the shank. For each of the plurality of rivets, the method comprises performing a machining operation on the tip the rivet or on the tail end of the slug from which the rivet was forged.