Spot Welding Expulsion Detection Using Electrode Resistance Statistics
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Solution Overview
Problem
Existing electric resistance welding methods struggle to accurately detect the expulsion phenomenon during spot welding of metal plates due to deflection of the welding gun, which complicates the determination of inter-electrode distance and makes it difficult to set appropriate welding conditions to prevent expulsion and subsequent cleaning requirements.
Innovation Solution
An expulsion detection method using energization resistance between electrodes, involving data accumulation, frequency distribution calculation, and statistical fitting with Gaussian functions to determine the occurrence of expulsion based on energization resistance reduction amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the inter-electrode distance is used to detect expulsion, then the detection can be performed based on welding geometry changes, but the welding gun deflection makes it difficult to measure with high accuracy
Solution Approach 1:
The patent replaces the mechanical measurement method (inter-electrode distance measurement) with an electrical measurement method (energization resistance measurement). By measuring the resistance between electrodes during welding, the system can detect expulsion without being affected by welding gun deflection, thereby maintaining high measurement precision while simplifying the measurement system.
Solution Approach 2:
The patent introduces energization resistance as an intermediary parameter to detect expulsion. Instead of directly measuring the physical distance between electrodes, the system measures the electrical resistance, which changes in response to expulsion events. This intermediary measurement approach eliminates the problem of welding gun deflection affecting measurement accuracy.
2Productivity
If visual inspection is used to detect expulsion, then the detection method is simple, but it is not feasible for production lines with large numbers of workpieces
Solution Approach 1:
The patent replaces visual inspection with an electrical measurement system that automatically detects expulsion through energization resistance changes. This substitution enables continuous, automated detection suitable for high-speed production lines while maintaining high detection accuracy, thus resolving the contradiction between productivity and measurement precision.
3Reliability
If the welding current is increased to prevent expulsion, then the expulsion occurrence can be reduced, but the welding condition must be precisely controlled to avoid over-correction
Solution Approach 1:
The patent implements a feedback control system that monitors energization resistance in real-time during welding and adjusts welding parameters accordingly. When expulsion is detected through resistance changes, the system can automatically adjust welding current or pressure to prevent recurrence, ensuring consistent welding quality without requiring complex manual control.
Solution Approach 2:
The patent uses preliminary measurement of energization resistance to predict potential expulsion issues before they occur. By analyzing resistance trends during the welding process, the system can take preventive actions such as adjusting welding parameters in advance, thereby maintaining reliable welding quality while simplifying the control strategy.
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
Enables accurate detection of expulsion with high precision, independent of welding gun deflection, by analyzing frequency distributions and statistical significance of Gaussian fittings, thereby improving the reliability of welding quality control.
Implementation Method 1
Contact portions of the plural metal plates are melted by Joule heat, which is generated by this energization
Data Source
AI summary
In electric resistance welding for energizing a workpiece formed by superimposing plural metal plates, an energization resistance reduction amount between a pair of electrodes pressurizing the workpiece is detected at a specified time interval during each welding process under a specified welding condition, frequency distribution of the energization resistance reduction amount under the welding condition is calculated on the basis of data relating to the energization resistance reduction amount, the frequency distribution is fitted with a Gaussian function, and occurrence of an expulsion under the welding condition is determined on the basis of whether the fitting is statistically significant.