Resistance Welding Current Branching Electrode
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Solution Overview
Problem
Resistance welding of stacked metal sheets with a thinnest workpiece on the outermost side often results in insufficient nugget growth due to inadequate Joule heat generation, leading to weak bonding and potential sputtering issues when increasing electric current or welding time.
Innovation Solution
A resistance welding method using a current branching electrode of opposite polarity to the primary electrodes, which branches the electric current to heat the thinnest workpiece effectively, preventing sputtering while ensuring sufficient nugget growth by controlling the electric current distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If electric current is increased to generate sufficient Joule heat in the thinnest workpiece, then nugget growth is improved, but sputtering occurs due to excessive current flowing through thicker workpieces
Solution Approach 1:
The electric current path is segmented into two separate paths: one through the thinnest workpiece (between first welding electrode and current branching electrode) and another through the stacked assembly (between first welding electrode and second welding electrode). This segmentation allows independent current control for each path, enabling sufficient current density in the thinnest workpiece without causing excessive current through thicker workpieces that would cause sputtering.
Solution Approach 2:
The current branching electrode acts as an intermediary element that branches the electric current from the first welding electrode. It provides an additional current path specifically through the thinnest workpiece, allowing precise control of current distribution. This intermediary enables the thinnest workpiece to receive adequate current for nugget growth while preventing harmful current concentrations in other workpieces.
2Temperature
If welding time is increased to generate sufficient Joule heat in the thinnest workpiece, then nugget growth is improved, but welding efficiency decreases
Solution Approach 1:
The invention changes the electrical parameter distribution by introducing a current branching electrode with opposite polarity. This creates two distinct current paths with different resistance characteristics, allowing the thinnest workpiece to experience higher current density and faster heating rate. Consequently, sufficient Joule heat is generated in the thinnest workpiece in a shorter time, maintaining high welding efficiency while ensuring adequate nugget growth.
3Temperature
If pressing force is reduced to allow better current distribution, then Joule heat generation in thinnest workpiece is improved, but bonding strength decreases
Solution Approach 1:
The pressing force application is segmented into two independent functions: the first welding electrode applies pressing force to ensure good contact at the current branching point, while the second welding electrode applies pressing force to ensure proper bonding of the stacked assembly. This segmentation allows each electrode to optimize its pressing force independently, enabling sufficient current distribution and Joule heat generation in the thinnest workpiece while maintaining adequate bonding strength through coordinated pressing forces.
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 achieves a larger nugget size with improved bonding strength across the interface between the thinnest and adjacent workpieces without causing sputtering, enhancing the efficiency and quality of the welded joint.
Implementation Method 1
the thinnest workpiece fails to generate a sufficient amount of Joule heat
Implementation Method 2
an electric current is passed between the welding electrodes in order to melt a region of the metal sheets near contact surfaces thereof
Data Source
AI summary
A resistance welding apparatus includes a welding gun having a first electrode tip serving as a first welding electrode, a second electrode tip serving as a second welding electrode, and a current branching electrode. The current branching electrode has an annular shape and is disposed in surrounding relation to the first electrode tip. The first electrode tip and the current branching electrode abut against a thinnest workpiece disposed on an outermost side of a stacked assembly that is resistance-welded by the resistance welding apparatus, and have opposite polarities to each other. When an electric current is passed from the first electrode tip to the second electrode tip and through the stacked assembly, a branched electric current flows from the first electrode tip to the current branching electrode.