Resistance Spot Welding With Direct Current Micro Pulses
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Solution Overview
Problem
Conventional resistance spot welding processes face challenges with unstable weld current ranges, limited electrode life, and inadequate weld joint strength, particularly when welding thin gauge USIBOR sheet metals and materials with heavy, oxidized coatings.
Innovation Solution
The method employs direct current micro pulses, with each pulse lasting from 1 to 10 milliseconds and separated by off-times of similar or varying duration, to apply a series of high-magnitude current pulses that extend electrode life and enhance weld current range, resulting in larger weld nugget sizes and stronger joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct current (DC) weld current mode is employed, then equipment size is reduced and controllability is improved, but weld current range becomes unstable and electrode life deteriorates rapidly
Solution Approach 1:
The patent applies periodic action by using alternating current (AC) instead of direct current (DC) to create periodic reversal of current direction. This periodic action prevents electrode adhesion and maintains stable weld current range, resolving the contradiction between equipment compactness and weld current stability. The AC waveform naturally provides periodic cleaning action on electrode surfaces without requiring additional mechanical components.
Solution Approach 2:
The patent changes the electrical parameter from DC to AC, fundamentally altering the current characteristics. This parameter change enables stable weld current range and extended electrode life while maintaining the compact MFDC equipment design, as the alternating current inherently prevents the electrode deterioration issues associated with DC welding.
2Device complexity
If direct current (DC) weld current mode is employed, then equipment size is reduced, but electrode life deteriorates much higher than AC
Solution Approach 1:
The patent utilizes periodic action through AC current to create regular reversal cycles that prevent electrode tip adhesion and deterioration. The periodic zero-crossing points in AC waveforms allow electrode surfaces to cool and clean naturally, significantly extending electrode life compared to continuous DC application, while maintaining compact equipment size.
Solution Approach 2:
By changing the current mode parameter from DC to AC, the patent fundamentally alters the electrode interaction characteristics. The alternating current parameter prevents continuous heating and adhesion buildup on electrode surfaces, thereby extending electrode life without requiring larger or more complex equipment.
3Reliability
If higher weld force, longer weld time and larger size electrodes are used, then weld current range is enlarged for DC welding, but electrode life improvement is very limited
Solution Approach 1:
The patent changes the fundamental current parameter from DC to AC, which simultaneously achieves both enlarged weld current range and extended electrode life. This parameter change eliminates the need for compensating measures like higher weld force or larger electrodes, as the AC waveform inherently provides both wide current range stability and electrode protection through periodic reversal.
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 significantly extends electrode life, enlarges the weld current range, and produces weld nuggets with finer microstructures and higher strength, making it suitable for diverse materials including those with heavy or oxidized coatings.
Implementation Method 1
passes weld current between the tips of the electrodes through the pieces of materials. As the weld current flows through the pieces of materials, the resistance of the materials to the current flow causes the materials to heat to their inherent melting point
Implementation Method 2
The resulting molten material solidifies under the predetermined clamping force to form the welded joint, or nugget
Data Source
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AI summary
Methods and systems for resistance spot welding using direct current micro pulses are described. One described method comprises comprising forming a weld joint by applying a plurality of direct current micro pulses to at least two pieces of materials through a first electrode and a second electrode.