Segmented Earth Electrode for Spot Welding
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Solution Overview
Problem
Existing earth electrode apparatuses for one-sided resistance spot welding face challenges in maintaining stable contact with irregular or inclined workpiece surfaces, leading to high current density and potential damage due to heat generation and wear, while also occupying excessive space and requiring large loads for deformation.
Innovation Solution
A compact earth electrode apparatus featuring a tiltable member with multiple shanks and detachable earth electrodes, which balances contact pressure across irregular surfaces and splits the welding current to reduce heat generation, incorporating a coolant reservoir for temperature management and easy maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a rigid copper plate is used as the earth electrode to provide large contact area, then heat generation due to conductive resistance is reduced, but point contact occurs due to surface irregularity leading to high current density and local damage
Solution Approach 1:
The earth electrode is divided into multiple segments (first earth electrode, second earth electrode, third earth electrode) arranged in an array. Each segment independently contacts the workpiece surface, ensuring that at least one segment maintains stable contact even when the surface is irregular or inclined, thereby preventing point contact and high current density.
Solution Approach 2:
The earth electrode segments are arranged in a two-dimensional array pattern rather than using a single large plate. This dimensional transformation allows the electrodes to distribute contact points across the workpiece surface, improving contact stability while maintaining adequate contact area to reduce heat generation.
2Reliability
If a flexible braided copper wire is used as the earth electrode to increase contact area, then current density is reduced, but the electrode becomes susceptible to deformation and wear
Solution Approach 1:
The earth electrode is segmented into multiple rigid electrodes arranged in an array. Each segment is structurally strong and resistant to deformation, while the array configuration ensures stable contact. This segmentation approach combines the contact stability benefit with structural durability, avoiding the wear and deformation issues of flexible braided wires.
3Reliability
If a curved laminated spring type earth electrode is used to adapt to workpiece surface shape, then contact area is improved, but the apparatus occupies large space and requires large load for deformation
Solution Approach 1:
Instead of using a single large deformable spring structure, the earth electrode is segmented into multiple smaller rigid electrodes arranged in an array. These segmented electrodes maintain stability without requiring large deformation loads or occupying excessive space, while still adapting to the workpiece surface through their distributed configuration.
Solution Approach 2:
The earth electrode array can be positioned and oriented to adapt to the workpiece surface geometry. The segmented structure allows for dynamic adjustment of contact points without requiring large-scale deformation, reducing the space and load requirements compared to a single large deformable spring.
4Temperature
If multiple earth electrodes are used to split welding current, then heat generation is reduced, but the device complexity increases
Solution Approach 1:
The earth electrode is segmented into multiple electrodes arranged in an array, with each segment connected to the power supply through a common connection. This segmentation distributes the welding current across multiple contact points, reducing heat generation at each point, while the simple array configuration and common connection minimize the increase in device complexity.
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 apparatus ensures stable contact and reduced heat generation, preventing damage to the workpiece and electrodes, while occupying minimal space and allowing for independent electrode replacement, thus improving welding quality and reducing maintenance costs.
Implementation Method 1
a tiltable member having a pedestal and first, second, and third shanks... the tiltable member tilts for balancing with the workpiece to ensure equal contact pressure
Implementation Method 2
A large electric current is applied for a certain period to the workpiece sandwiched between a pair of weld electrodes... A nugget is formed due to heat generated at a weld region
Implementation Method 3
an earth electrode 106 is brought into contact with the second plate member 102 in a conductive manner... a welding current application route X, which leads from the weld electrode 105 to the earth electrode 106
Implementation Method 4
incorporating a coolant reservoir for temperature management
Data Source
AI summary
In an earth electrode apparatus, a cradle having first, second, and third shanks to which first, second, and third earth electrodes can be attached respectively is coupled to a shaft supported by a base. The cradle is coupled thereto in a tiltable manner. If the surface of a workpiece is irregular or inclined, the cradle tilts for balancing with the workpiece to ensure equal contact pressure for the contact of the first, second, and third earth electrodes with the workpiece, thereby offering stable contact irrespective of surface irregularity or inclination. Since a welding current is split to flow into the first, second, and third earth electrodes through respective points of contact thereof with the workpiece, it is possible to reduce current density at each of the points of contact and to avoid heat generation ascribable to conductive resistance at each of the points of contact.