Resistance Welding Electrode Dressing via Resistance Waveform Analysis
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Solution Overview
Problem
Existing methods for determining the dressing quality of resistance welding electrodes based solely on resistance values at a specific time can lead to false determinations due to variations in resistance waveforms over time and electrode wear, making it difficult to set appropriate threshold values for ensuring welding strength.
Innovation Solution
A method and device that accumulate known resistance waveforms before and after dressing, using statistical models to set threshold values for determining dressing quality by comparing unknown waveforms against these models, incorporating probability density functions and Mahalanobis distances to assess abnormality and false detection rates, and re-determining quality based on negative log-likelihood calculations across successive welding points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If dressing quality is determined based only on resistance value at a certain time immediately after applying current, then determination process is simple, but false determination occurs due to gap between metal plates influencing resistance value
Solution Approach 1:
The patent transitions from determining dressing quality based on a single resistance value at one time point to analyzing the entire resistance waveform across multiple time points during welding. This dimensional expansion from scalar to temporal waveform analysis enables accurate determination by considering the overall resistance characteristics rather than being misled by transient effects at specific moments.
2Measurement precision
If threshold value is set for dressing quality determination based on resistance waveform, then determination accuracy improves, but it becomes difficult to appropriately set threshold value due to waveform variations at different welding points and over time
Solution Approach 1:
The patent implements a dynamic threshold setting mechanism that automatically adapts to different welding points and time conditions. Instead of using fixed threshold values, the system dynamically determines appropriate thresholds based on the specific welding point characteristics and temporal variations, eliminating the need for manual threshold adjustment while maintaining high determination accuracy across diverse operating conditions.
3Reliability
If resistance waveform analysis is used for dressing quality determination, then false detection rate decreases, but analysis complexity increases
Solution Approach 1:
The patent replaces complex manual waveform analysis with automated computational processing. The determination unit automatically compares measured resistance waveforms against reference waveforms using computational algorithms, eliminating the need for manual interpretation while achieving high reliability in dressing quality determination. This substitution of automated computational methods for manual analysis reduces both complexity and false detection rates.
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 approach allows for accurate and reliable dressing quality determination, reducing false detection rates and ensuring consistent welding strength by considering the variability of resistance waveforms at each welding point, thereby improving the efficiency and accuracy of the dressing process without extending production time.
Implementation Method 1
a measurement unit for measuring a resistance value of an electrically conducting medium when a current is applied to the electrically conducting medium through the pair of electrodes
Implementation Method 2
Joule heat due to electrical resistance is generated in the plurality of metal plates, and portions in contact with the electrodes locally melt
Data Source
AI summary
To accurately make a dressing quality determination based on resistance waveforms, a dressing quality determination method determines the quality of dressing performed for electrodes when resistance welding is performed at a plurality of welding points. This method includes accumulating a known resistance waveform immediately after dressing the electrodes, and a known resistance waveform immediately before dressing the electrodes; creating, by a statistical method, a model for setting a threshold value for dressing quality determination, based on a plurality of known resistance waveforms immediately after dressing and a plurality of known resistance waveforms immediately before dressing; acquiring an unknown resistance waveform immediately after dressing the electrodes; and determining whether dressing is normal or dressing is abnormal by comparing the unknown resistance waveform immediately after dressing with the threshold value for dressing quality determination.