Resistance Spot Welding Heat-Pattern Control for Stable Nugget Size
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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 the welding process.
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 during actual welding based on an electrode force parameter to match the heat pattern, ensuring a stable nugget diameter by compensating for differences in heat generation patterns caused by disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the same welding current is used throughout the welding process, then the initial nugget diameter can be controlled appropriately, but the nugget diameter decreases over time due to electrode wear and contact area widening
Solution Approach 1:
The patent applies dynamics by transitioning from static welding parameters to dynamic adaptive control. The welding current is continuously adjusted based on real-time monitoring of voltage, current, and time data, allowing the system to compensate for electrode wear and maintain consistent nugget diameter throughout the electrode's service life without requiring frequent dressing or replacement
Solution Approach 2:
The patent implements feedback control by monitoring welding parameters (voltage, current, time) in real-time and using this information to adjust the welding current dynamically. The system compares actual welding data with target values and modifies subsequent welding cycles to maintain quality, creating a closed-loop control system that adapts to electrode wear and varying conditions
2Manufacturing precision
If a high welding current is set beforehand to compensate for current shunting, then a sufficient nugget diameter can be obtained, but expulsion occurs due to excessive heat generation
Solution Approach 1:
The patent uses dynamic current adjustment rather than a fixed high current setting. By monitoring welding parameters in real-time and adapting the current waveform to actual conditions, the system delivers sufficient current to overcome shunting when needed while avoiding excessive heat generation that causes expulsion, achieving optimal nugget formation without harmful side effects
Solution Approach 2:
The patent changes welding parameters dynamically based on detected conditions. The system monitors voltage, current, and time characteristics and adjusts welding parameters including current magnitude and waveform shape in response to detected conditions such as current shunting, preventing both insufficient heating and excessive heat generation
3Adaptability or versatility
If the welding current is increased to compensate for sheet gap, then welding can proceed with misaligned sheets, but the nugget diameter becomes unstable and expulsion risk increases
Solution Approach 1:
The patent applies dynamic control to adapt to sheet gap conditions. By monitoring welding parameters in real-time and adjusting the current waveform based on detected conditions, the system maintains stable nugget diameter even when sheets are misaligned, avoiding the expulsion problems associated with fixed high current settings
Solution Approach 2:
The system changes welding parameters dynamically in response to detected sheet gap conditions. By monitoring voltage, current, and time characteristics and adjusting parameters accordingly, the system achieves both adaptability to misalignment and stability of nugget formation
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 desired nugget diameter without expulsion, even in the presence of significant disturbances, improving operating efficiency and yield rates in continuous welding processes like vehicle manufacturing.
Implementation Method 1
Heat generated from the resistance to the flow of the high welding current is used to obtain a spot weld
Data Source
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.