Resistance Spot Welding Control for Stable Nuggets Without Expulsion
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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 sheet gaps occur, due to variations in electrode wear and disturbance states during vehicle manufacturing.
Innovation Solution
A resistance spot welding method involving test welding under various conditions to store time variation curves of heat generation, followed by adaptive control during actual welding based on the disturbance state, ensuring optimal heat distribution and preventing expulsion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the same welding condition is used throughout continuous welding, then the initial welding quality is maintained, but the nugget diameter decreases due to electrode wear and contact area widening
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 contact area widening, maintaining consistent nugget diameter throughout the electrode's service life
Solution Approach 2:
The system uses feedback from the welding operation count to automatically adjust welding parameters. The control unit monitors the number of welding operations and automatically modifies the welding current accordingly, eliminating the need for manual intervention or pre-set patterns for each welding condition
2Manufacturing precision
If a high welding current is set beforehand to compensate for current shunting, then the nugget diameter requirement is met, but expulsion occurs due to excessive heat generation
Solution Approach 1:
The welding current is adjusted dynamically based on real-time detection of disturbance states. The control unit detects current shunting and sheet gaps, then optimizes the welding current to generate sufficient heat for proper nugget formation without excessive heat that would cause expulsion
Solution Approach 2:
The system changes welding parameters (current, time) based on detected disturbance conditions. By detecting the presence of current shunting or sheet gaps and adjusting parameters accordingly, the system achieves the required nugget diameter while preventing expulsion through optimized heat generation
3Manufacturing precision
If predetermined welding current change patterns are set for electrode wear compensation, then the nugget diameter can be maintained, but considerable time and cost are required to derive patterns for numerous welding conditions
Solution Approach 1:
The welding device performs self-adjustment based on the number of welding operations. The control unit automatically increases the welding current after predetermined numbers of welding operations, eliminating the need for external setup of complex patterns for different welding conditions and reducing both time and cost
Solution Approach 2:
The system uses a universal dynamic adjustment mechanism that adapts to different welding conditions through automatic current increase based on operation count. This single adaptable mechanism replaces the need for multiple predetermined patterns, simplifying the setup process while maintaining nugget diameter consistency
4Adaptability or versatility
If a larger sheet gap exists between steel sheets, then the contact diameter decreases, but this facilitates expulsion during welding
Solution Approach 1:
The system detects sheet gaps and adjusts welding parameters (current and time) accordingly. By optimizing parameters based on the detected gap size, the system maintains sufficient contact pressure and heat generation to prevent expulsion even when larger sheet gaps are present
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 stabilizes nugget diameter and prevents expulsion even under significant disturbance conditions, improving operating efficiency and yield rate in vehicle manufacturing by adapting to variations in disturbance states during continuous welding.
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
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AI summary
A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding. The test welding is performed under each of two or more welding conditions. In the test welding, preliminary current passage and main current passage are performed by constant current control, and an electrical property between the electrodes in the preliminary current passage and a time variation curve of an instantaneous amount of heat generated per unit volume, etc. in the main current passage are stored. In the actual welding, preliminary current passage is performed by constant current control in the same current pattern as in the preliminary current passage of the test welding, an electrical property between the electrodes in the preliminary current passage in the actual welding and an electrical property between the electrodes stored in the preliminary current passage in the test welding are compared for each welding condition to set a target in main current passage in the actual welding, and thereafter adaptive control welding is performed to control a current passage amount as the main current passage.