Resistance Spot Welding Current Control for Gap-Robust Nugget Growth
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Solution Overview
Problem
Conventional resistance spot welding methods struggle to enlarge the nugget diameter to the target value when disturbances such as gaps exist between the plates being welded.
Innovation Solution
A current control method that involves sequentially acquiring electrical resistance, calculating expansion amount, and determining current application based on the difference between the computational nugget diameter and a master computational nugget diameter to achieve the target nugget diameter despite disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional resistance spot welding method is used with constant current control, then the welding process is simple, but the nugget diameter cannot be enlarged to the target value when gaps exist between plates
Solution Approach 1:
The patent implements a feedback control mechanism where the welding current is continuously adjusted based on real-time measurements of electrical resistance and expansion amount. The control device calculates the difference between the actual nugget diameter (derived from resistance and expansion) and the target nugget diameter, then modifies the welding current accordingly to compensate for deviations caused by gaps or other disturbances, ensuring the nugget reaches the target diameter despite initial conditions
Solution Approach 2:
The patent dynamically changes welding parameters (current, voltage, time) based on real-time monitoring of electrical resistance and expansion amount. By adjusting these parameters during the welding process rather than maintaining constant values, the system adapts to disturbances such as gaps between plates, enabling the nugget diameter to reach the target value even when initial conditions are unfavorable
2Manufacturing precision
If real-time current adjustment is implemented based on resistance and expansion monitoring, then the nugget diameter can reach target value despite gaps, but the control system complexity increases
Solution Approach 1:
The control device performs self-adjustment by automatically calculating the nugget diameter from measured electrical resistance and expansion amount, determining the required current adjustment, and applying the corrected current without external intervention. This self-service capability reduces the need for complex external control systems while achieving precise nugget diameter control
Solution Approach 2:
The control device integrates multiple functions into a single system: it monitors electrical resistance, measures expansion amount, calculates nugget diameter, determines required current adjustments, and controls the welding power source. This multi-functionality consolidates what could be separate complex systems into one integrated unit, managing device complexity while achieving precise control
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
The method effectively enlarges the nugget diameter to the target value even with gaps, enhancing weld strength by accurately controlling current application during welding.
Implementation Method 1
resistance spot welding in which a plurality of overlapped metal plates are welded together by being sandwiched between a pair of electrodes and energized while applying pressure thereto
Data Source
AI summary
Provided is a current control method for resistance spot welding in which a plurality of overlapped metal plates are welded together by being sandwiched between a pair of electrodes and energized while applying pressure. The current control method includes sequentially acquiring an electrical resistance between the pair of electrodes during welding; sequentially calculating an expansion amount caused by the welding using a strain calculated from the pressure applied by the electrodes and a stroke of the electrode; sequentially calculating a computational nugget diameter by using the electrical resistance and the expansion amount, the computational nugget diameter being a diameter of a nugget formed during the welding; and sequentially determining a current to be applied between the pair of electrodes during the welding using a difference between the computational nugget diameter and a master computational nugget diameter calculated in master welding in which no gap exists between the metal plates and a nugget with a target diameter is obtained by the welding.