Resistance Welding Current Stop Control via Electrode Displacement
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Solution Overview
Problem
In resistance welding, existing systems face challenges in ensuring the quality of the welding process by accurately determining when the members to be welded have reached the melting point, leading to potential defects and inefficiencies, especially in mass production of dissimilar materials like aluminum and steel.
Innovation Solution
A resistance welding control system that includes a pair of electrodes with a driving mechanism and a control device equipped with a detector, determining unit, and stop controller, which detects the position or distance between electrodes to determine if a predetermined variation has occurred, indicating the feature point temperature, and stops the electricity supply accordingly to ensure proper melting and congealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser displacement sensor is used to measure displacement of welding portion, then welding quality can be monitored, but device complexity and cost increase
Solution Approach 1:
The system uses the existing motor's encoder to detect electrode position, which automatically provides the necessary measurement function without requiring additional sensors. The encoder serves dual purposes: motor control feedback and welding temperature indication, making the system self-sufficient for quality monitoring
Solution Approach 2:
The encoder originally designed for motor control is made to serve multiple functions: it controls the motor positioning and simultaneously indicates the welding portion temperature through electrode displacement correlation. This multi-functionality eliminates the need for separate temperature sensors
2Device complexity
If electrode position is detected using existing encoder, then system complexity is reduced, but measurement precision for welding temperature indication is limited
Solution Approach 1:
The system introduces an intermediate relationship between electrode displacement and welding temperature. The encoder measures electrode position, which serves as an intermediary indicator that correlates with welding portion temperature through thermal expansion and material properties, allowing indirect temperature measurement without direct contact
3Stress or pressure
If welding pressure is controlled by managing motor torque, then welding pressure control is achieved, but response time to temperature changes is delayed
Solution Approach 1:
The system implements feedback control by continuously monitoring electrode position through the encoder and using this information to determine when to stop current supply. The real-time position data provides immediate feedback on welding progress, allowing the system to respond quickly to temperature changes and prevent overheating or insufficient welding
Solution Approach 2:
The system dynamically adjusts the welding process by transitioning from fixed-time current supply to dynamic current supply control based on real-time electrode position. The current supply duration is continuously optimized based on the detected electrode displacement, making the welding process adaptive to varying material properties and conditions
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 solution ensures reliable melting and congealing of the welding portions, improving the quality of the welds and enabling efficient mass production, particularly in dissimilar metal welding, without requiring additional sensors or increasing system complexity.
Implementation Method 1
a detector configured to detect a position of the first electrode or a distance from the first electrode to the second electrode in the approaching-separating direction while electricity is being passed between the first and second electrodes
Implementation Method 2
The predetermined variation indicates that a temperature of the member to be welded is at a feature point temperature
Implementation Method 3
resistance welding, which is also called spot welding in general, is achieved as mainly joule heat produced by contact resistance between the members to be welded melts the members to be welded
Data Source
AI summary
A resistance welding control system includes a pair of electrodes, a driving mechanism, and a control device. The control device includes a detector, a determining unit, and a stop controller. The detector is configured to detect a position of a first electrode of the pair of electrodes and a distance from the first electrode to a second electrode of the pair of electrodes in the approaching-separating direction while electricity is being passed between the first and second electrodes. The determining unit is configured to make a determination as to whether predetermined variation has occurred in the position or the distance. The predetermined variation indicates that a temperature of the member to be welded is at a feature point temperature. The stop controller is configured to stop the electricity passed between the first and second electrodes on the basis of a result of the determination.