Resistance Spot Welding Force Control for Stable Nugget Diameter
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Solution Overview
Problem
Existing resistance spot welding methods fail to consistently achieve a desired nugget diameter without expulsion, especially when disturbances such as significant gaps between metal sheets or current shunting occur, due to variations in electrode wear and complex calculation requirements for temperature distribution estimation.
Innovation Solution
The method involves setting an initial electrode force and adjusting it based on the average or time integration value of resistance between electrodes after an intermediate welding time, optimizing the electrode force to mitigate disturbances and ensure a stable nugget diameter without expulsion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the welding current is increased to compensate for electrode wear, then the nugget diameter can be maintained, but the current density distribution becomes uneven and expulsion risk increases
Solution Approach 1:
The patent applies dynamics by making the electrode force adjustable during the welding process. The electrode force is initially set to a first value, then changed to a second value (higher than the first) after a predetermined time during current passage. This dynamic adjustment compensates for electrode wear effects and maintains stable nugget diameter without causing expulsion, resolving the contradiction between maintaining precision and ensuring reliability.
Solution Approach 2:
The patent changes the electrode force parameter during the welding process. By increasing the electrode force from a first value to a second value after a predetermined time, the system compensates for electrode wear and maintains stable welding conditions. This parameter change ensures consistent current density distribution and prevents expulsion while maintaining nugget diameter precision.
2Reliability
If the electrode force is increased to prevent expulsion, then weld reliability improves, but the contact area increases and current density decreases
Solution Approach 1:
The patent uses dynamic adjustment of electrode force, changing it from a first value to a second value (higher than the first) after a predetermined time during current passage. This timing-based dynamic control prevents expulsion while maintaining appropriate current density for nugget formation, resolving the contradiction between reliability and manufacturing precision.
Solution Approach 2:
The patent applies preliminary action by setting the electrode force to a first value before current passage begins, then adjusting it to a second value after a predetermined time. This preliminary setup and subsequent adjustment ensure that the electrode force is optimized at each stage of the welding process, preventing expulsion while maintaining current density precision.
3Manufacturing precision
If the welding current is increased to account for disturbances, then nugget diameter is maintained, but energy consumption increases and process complexity increases
Solution Approach 1:
The patent applies dynamics by adjusting the electrode force during the welding process rather than continuously increasing welding current. The electrode force is changed from a first value to a second value after a predetermined time, which maintains nugget diameter consistency while avoiding excessive energy consumption associated with high current settings.
Solution Approach 2:
The patent changes the electrode force parameter during welding to compensate for disturbances and maintain nugget diameter. By adjusting electrode force rather than welding current, the system achieves manufacturing precision with more efficient energy utilization.
4Manufacturing precision
If the electrode force is adjusted frequently to compensate for wear, then welding precision is maintained, but production time increases
Solution Approach 1:
The patent applies dynamics by adjusting the electrode force during the welding process rather than requiring frequent stops for electrode dressing. The electrode force is changed from a first value to a second value after a predetermined time during current passage, maintaining nugget diameter precision while ensuring continuous production and high productivity.
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 stable attainment of a desired nugget diameter regardless of disturbances, improving operating efficiency and yield rate by effectively responding to variations in the disturbance state during continuous welding.
Implementation Method 1
heat generated from the resistance to the flow of the high welding current is used to form a spot weld
Implementation Method 2
squeezing two or more overlapping steel sheets by a pair of electrodes from above and below and, while applying an electrode force
Implementation Method 3
The spot weld is called a nugget, which results from the overlapping steel sheets melting and solidifying at their contact portion
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
Provided is a resistance spot welding method by which a desired nugget diameter can be stably obtained without expulsion even when the effect of a disturbance is significant. An electrode force FA of a main current passage after an intermediate welding time Ta is set based on an average value or time integration value RA of a resistance between electrodes from the start of main current passage to the intermediate welding time Ta.