Adaptive Resistance Spot Welding Under Shunting and Sheet Gaps
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Solution Overview
Problem
Existing resistance spot welding methods fail to consistently achieve a stable nugget diameter without expulsion, especially when disturbances such as current shunting or significant sheet gaps occur, due to variations in electrode wear and disturbance states during welding.
Innovation Solution
A resistance spot welding method that involves performing test welding under various conditions to store time variation curves of heat generation, and then using adaptive control to adjust the current passage based on the electrode force parameter to match the target heat pattern, ensuring a stable nugget diameter even with significant disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the same welding current is used throughout electrode life, then the initial welding quality is maintained, but the nugget diameter decreases due to electrode wear and current density reduction
Solution Approach 1:
The welding current is dynamically adjusted based on the number of welding operations performed. The control unit increases the welding current in steps after predetermined numbers of welding operations to compensate for electrode wear and maintain current density, transforming a static welding parameter into a dynamic one that adapts to electrode degradation
Solution Approach 2:
The control unit monitors the number of welding operations and uses this information to automatically adjust the welding current. This feedback mechanism ensures that the welding current is increased appropriately to maintain nugget diameter consistency without requiring manual intervention or electrode replacement
2Reliability
If a high welding current is set beforehand to compensate for current shunting, then nugget formation is improved, but expulsion is more likely to occur
Solution Approach 1:
The welding current is applied dynamically in multiple steps rather than as a single high current. The control unit first applies a relatively low current to form a stable nugget, then increases the current in subsequent steps to achieve the required nugget diameter while avoiding expulsion that would result from immediate high current application
Solution Approach 2:
The welding current is applied in periodic steps with intermediate intervals. The control unit divides the welding process into multiple current application phases, allowing the nugget to grow progressively while maintaining thermal stability and preventing the sudden heat input that causes expulsion
3Manufacturing precision
If welding current is increased to compensate for sheet gap, then nugget diameter is maintained, but energy consumption increases
Solution Approach 1:
The welding current is dynamically adjusted in response to detected disturbances such as sheet gaps. The control unit monitors welding parameters and increases current selectively when gaps are detected, rather than maintaining a continuously high current, thereby maintaining nugget stability while minimizing unnecessary energy consumption
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 effectively maintains a consistent nugget diameter without expulsion, even in the presence of disturbances like current shunting or large sheet gaps, by optimizing the heat generation pattern during actual welding based on the stored data from test conditions.
Implementation Method 1
Heat generated from the resistance to the flow of the high welding current is used to obtain a spot weld. The spot weld is called a nugget, and results from the overlapping steel sheets melting and solidifying at their contact portion when the current flows through the steel sheets.
Data Source
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AI summary
A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding, wherein the test welding is performed under each of two or more welding conditions. In the test welding, for each of the welding conditions, an electrode force parameter from when electrode force application to parts to be welded starts to when a set electrode force is reached before start of current passage and a time variation curve of an instantaneous amount of heat generated and a cumulative amount of heat generated are stored. In the actual welding: electrode force application to the parts to be welded is performed under each of the same conditions as in the test welding before start of current passage, and a corresponding electrode force parameter and the parameter stored in the test welding are compared for each of the welding conditions to set a target of a time variation curve of an instantaneous amount of heat generated and a cumulative amount of heat generated in the actual welding; and adaptive control welding is performed to control a current passage amount according to the target.