Spot Welding Nugget Control via Dynamic Pressing Force
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Solution Overview
Problem
In spot welding of laminated bodies, the nugget preferentially grows between thick-walled workpieces due to higher electric resistance, potentially leaving thin-walled workpieces un-integrated, and existing solutions require an auxiliary electrode that complicates the device and limits space for application.
Innovation Solution
A spot welding method and device that varies the pressing forces between the first and second welding tips to control the growth of the nugget, ensuring integration of all workpieces without an auxiliary electrode, by adjusting the contact resistance to promote nugget growth at points of high resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an auxiliary electrode is added to control nugget growth, then the nugget can be made to grow toward thin-walled workpieces, but the device complexity increases and the available space for welding decreases
Solution Approach 1:
The patent changes the pressing force parameters applied by welding tips during the welding process. By dynamically adjusting the pressing forces of multiple welding tips at different stages (initial pressing, intermediate pressing, final pressing), the method controls nugget growth direction without adding auxiliary electrodes, thus resolving the contradiction between manufacturing precision and device complexity
Solution Approach 2:
The patent implements dynamic control of pressing forces during the welding process. The pressing forces are not static but are adjusted in three distinct stages to control nugget growth. This dynamic approach replaces the static auxiliary electrode solution, achieving precise nugget control while maintaining simpler device structure
2Manufacturing precision
If an auxiliary electrode is added to control nugget growth, then the nugget can be made to grow toward thin-walled workpieces, but the available space for welding decreases
Solution Approach 1:
By changing pressing force parameters instead of adding physical auxiliary electrodes, the method achieves nugget control without occupying additional welding space, thus resolving the contradiction between manufacturing precision and available welding space
3Ease of operation
If equal pressing forces are applied to both welding tips, then the device operation is simplified, but the nugget does not grow to the contact surfaces of thin-walled workpieces
Solution Approach 1:
The patent segments the welding process into three distinct stages with different pressing force configurations: initial pressing stage, intermediate pressing stage, and final pressing stage. This segmentation allows precise control of nugget growth at each stage while maintaining relatively simple operation procedures, resolving the contradiction between ease of operation and manufacturing precision
Solution Approach 2:
The patent applies periodic action by alternating the pressing force relationships between welding tips across three stages. The pressing forces are periodically adjusted from equal to unequal and back to equal, creating a rhythmic control pattern that ensures complete nugget growth while keeping the control logic systematic and manageable
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 allows for complete integration of all workpieces with excellent joint strength, even in narrow spaces, simplifying the device configuration and eliminating the need for an auxiliary electrode.
Implementation Method 1
heat generated by energization of the thick-walled workpieces 2, 3 is larger than that of the thin-walled workpieces 4, 5
Implementation Method 2
the first pressing force to be applied to the laminated body from the first welding tip brought into contact with the thin-walled workpiece smaller than a second pressing force to be applied to the laminated body from the second welding tip brought into contact with the thick-walled workpiece
Data Source
AI summary
In the present invention, while a welding current is applied with respect to a laminate body comprising thick metal plates and thin metal plates, a first welding pressure (F1) with respect to the laminate body from an upper tip contacting the metal plate and a second welding pressure (F2) with respect to the laminate body from a lower tip contacting the metal plate are changed relative to each other. Specifically, F1<F2 in a first step which is an initial period of welding, F1=F2 in a second step which is an intermediate period of welding, and F1>F2 in a third step which is a final period of welding.