Resistance Spot Welding Force Feedback for Stable Nugget Growth
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Solution Overview
Problem
Existing resistance spot welding methods struggle to ensure stable nugget diameter, especially in the presence of work disturbances like sheet gaps, and often result in expulsion, which reduces joint strength.
Innovation Solution
A resistance spot welding device that measures electrode force in real-time and controls the electric current supply by suspending and resuming it based on specific force ratios to prevent expulsion and achieve a larger nugget diameter, using a controller to manage the electrode force within defined ranges during the welding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If electric current is increased to increase nugget diameter, then nugget size is improved, but expulsion occurrence increases
Solution Approach 1:
The patent applies periodic action by dividing the electric current supply into multiple stages with different current values. The welding process uses an initial current value to start nugget formation, then switches to a second current value to continue heating, and optionally a third current value for final nugget growth. This periodic variation in current supply allows the nugget to grow to the desired diameter while preventing expulsion by controlling the heating rate at each stage.
Solution Approach 2:
The patent changes the parameter of electric current value during the welding process. Instead of using a single constant current value, the system varies the current through multiple stages (initial, second, and optionally third current values). This parameter change enables precise control over the heating process, allowing the nugget to reach the target diameter without causing expulsion.
2Device complexity
If conventional welding methods are used on galvanized steel sheets, then welding process is simple, but expulsion is likely to occur
Solution Approach 1:
The patent applies periodic action by implementing multi-stage electric current supply with different current values. The welding process starts with an initial current value, then switches to a second current value, and optionally a third current value. This periodic variation in current supply prevents expulsion in galvanized steel sheets while maintaining a relatively simple welding process structure.
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 device effectively prevents expulsion and ensures a stable, large nugget diameter even with work disturbances, enhancing the strength and reliability of the weld joint.
Implementation Method 1
an electric current is applied under pressure to melt a contact region between the steel sheets 1 and 2
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A resistance spot welding method is provided, which allows a large nugget to be formed while the occurrence of expulsion is prevented. The resistance spot welding device according to the present invention is a resistance spot welding device for welding at least two overlapping steel sheets held between a pair of welding electrodes. The resistance spot welding device includes the pair of electrodes, an electrode force gauge that measures an electrode force, and a controller that controls an electric current supply to the electrodes according to the electrode force measured by the electrode force gauge. The controller controls the electric current such that the electrode force F measured by the electrode force gauge after the start of the electric current supply is adjusted to a prescribed value.