Adaptive Resistance Spot Welding for Disturbance-Stable Nuggets
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Solution Overview
Problem
Existing resistance spot welding methods struggle to consistently achieve a desired nugget diameter and joint strength, especially when disturbances such as current shunting or sheet gaps occur, and are costly and complex to implement, particularly when dealing with high-strength steel sheets.
Innovation Solution
A resistance spot welding method involving test welding to store heat generation curves, followed by adaptive control in actual welding, optimizing voltage ratios and heat treatment to compensate for disturbances, ensuring stable nugget diameter and joint strength in high-strength steel sheet combinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional resistance spot welding is used with fixed welding parameters, then the process is simple and fast, but the nugget diameter becomes unstable when disturbances such as current shunting or sheet gaps occur
Solution Approach 1:
The system performs preliminary test welding before actual welding to measure the electrical properties (resistance and inductance) of the workpiece. Based on these measurements, the welding parameters are determined in advance to compensate for disturbances like current shunting and sheet gaps, ensuring stable nugget diameter without complex real-time control during welding.
Solution Approach 2:
The system uses feedback from test welding measurements (resistance and inductance values) to adjust welding parameters. The measured electrical properties provide information about the actual workpiece state, which is used to determine appropriate welding current and time to achieve consistent nugget diameter despite variations in sheet combination or assembly conditions.
2Manufacturing precision
If welding current is increased to compensate for current shunting, then nugget diameter can be maintained, but the risk of expulsion and surface damage increases
Solution Approach 1:
The system changes welding parameters (current and time) based on measured electrical properties from test welding. By determining parameters that account for current shunting effects in advance, the system achieves proper nugget diameter control without excessive current that would cause expulsion or surface damage.
Solution Approach 2:
The system performs preliminary test welding to measure resistance and inductance, then determines appropriate welding parameters before actual welding. This preliminary measurement and calculation prevents the need for excessive current compensation during welding, avoiding expulsion and surface damage while maintaining nugget quality.
3Reliability
If electrode force is increased to improve contact, then nugget formation improves, but the risk of sheet deformation and equipment wear increases
Solution Approach 1:
The system determines optimal electrode force based on measured electrical properties from test welding. By calculating the appropriate force needed for each specific workpiece configuration, the system achieves consistent weld quality without excessive force that would cause sheet deformation or accelerated electrode wear.
4Reliability
If test welding and adaptive control are implemented, then welding quality under disturbances improves, but the welding cycle time increases
Solution Approach 1:
The system performs brief test welding and parameter determination before actual welding. This preliminary measurement phase is short compared to the actual welding process, and it enables high-quality welding under disturbances without significantly extending the overall cycle time, maintaining productivity while improving reliability.
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 enhances joint strength in high-strength steel sheet welds, even with disturbances, improving operational efficiency and yield rates in continuous welding processes.
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
Figure 1A~1F
Figure 2A~2B
Figure 3A~3B
AI summary
A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding, wherein in the test welding, 0.2 ≤ Vtp/Vtm ≤ 1.5 is satisfied where Vtm is an average value of a voltage between the electrodes in main current passage in the test welding and Vtp is an average value of a voltage between the electrodes in subsequent current passage in the test welding, and in each of main current passage and subsequent current passage in the actual welding, a time variation curve of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume that are stored in a corresponding one of the main current passage and the subsequent current passage in the test welding are set as a target, and adaptive control welding is performed to control a current passage amount according to the target.