Resistance Spot Welding Heat Control to Prevent Expulsion
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Solution Overview
Problem
Resistance spot welding methods fail to consistently achieve an appropriate nugget diameter due to disturbances such as electrode wear, current shunting, and sheet gaps, leading to expulsion and inadequate heat generation, especially in complex sheet combinations with significant thickness ratios.
Innovation Solution
A resistance spot welding method that involves test welding to calculate and store heat generation patterns, followed by adaptive control in actual welding, where the current pattern is divided into steps, and the target heat generation is adjusted based on detected expulsion, using a reduced cumulative heat target and adjusted current and voltage to prevent further expulsion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the same welding current is used throughout electrode life, then initial weld quality is maintained, but nugget diameter decreases as electrodes wear
Solution Approach 1:
The welding current is dynamically adjusted based on the number of welding operations performed. The control unit increases the welding current in steps as electrodes wear, compensating for reduced current density and maintaining consistent nugget diameter throughout electrode service life.
Solution Approach 2:
The system uses feedback from the welding operation count to automatically adjust welding parameters. The control unit monitors the number of welding points and automatically modifies the welding current pattern, eliminating the need for manual intervention or pre-setting complex patterns for different electrode wear stages.
2Manufacturing precision
If welding current is increased to compensate for electrode wear, then nugget diameter is maintained, but energy consumption increases
Solution Approach 1:
The welding current is dynamically adjusted based on the number of welding operations performed. The control unit increases the welding current in steps as electrodes wear, compensating for reduced current density and maintaining consistent nugget diameter throughout electrode service life.
Solution Approach 2:
The system changes the welding current parameter in response to electrode wear. By automatically adjusting the current pattern based on the number of welding points, the system optimizes energy usage while maintaining weld quality, avoiding both excessive energy consumption and insufficient heating.
3Manufacturing precision
If high welding current is set beforehand to compensate for current shunting, then nugget diameter requirement is met, but expulsion occurs more easily
Solution Approach 1:
The welding current is dynamically adjusted based on the number of welding operations performed. The control unit increases the welding current in steps as electrodes wear, compensating for reduced current density and maintaining consistent nugget diameter throughout electrode service life.
Solution Approach 2:
The welding current is applied in a periodic manner with multiple steps. By dividing the welding process into stages and adjusting current in each step, the system generates heat progressively, preventing sudden excessive heating that causes expulsion while ensuring adequate nugget formation.
4Manufacturing precision
If complex welding current patterns are pre-set for different electrode wear stages, then weld quality is maintained, but setup time and cost increase
Solution Approach 1:
The welding device performs self-adjustment of welding parameters based on the number of welding operations. The control unit automatically modifies the welding current pattern according to electrode wear, eliminating the need for external setup or pre-programming of complex patterns for different wear stages.
Solution Approach 2:
The system uses feedback from the welding operation count to automatically adjust welding parameters. The control unit monitors the number of welding points and automatically modifies the welding current pattern, eliminating the need for manual intervention or pre-setting complex patterns for different electrode wear stages.
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 effectively prevents further expulsion and ensures an appropriate nugget diameter is obtained even when disturbances occur, by recalculating the target heat generation based on voltage and resistance changes during welding.
Implementation Method 1
Heat generated from the resistance to the flow of the high welding current is used to obtain a spot weld
Data Source
Figure 1A~1C
Figure 2
Figure 3A~3B
AI summary
A stored time variation curve and cumulative amount of heat generated of each step are each used as a target. In the case where a time variation of an instantaneous amount of heat generated per unit volume differs from the time variation curve in any of the steps, a current passage amount is controlled in order to compensate for the difference within a remaining welding time in the step so that a cumulative amount of heat generated per unit volume in actual welding matches the stored cumulative amount of heat generated in the test welding. Further, in the case where expulsion is detected in any of the steps, then in subsequent welding, the cumulative amount of heat generated per unit volume used as the target is reduced, and the current passage amount is adjusted in accordance with the reduced cumulative amount of heat generated per unit volume.