Spot Welding Gun Motion Control for Low-Load Workpiece Detection
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Solution Overview
Problem
In spot welding, a large load applied to the workpiece during detection can deform it, and vibration and path deviation of the welding gun can affect weld quality and alignment.
Innovation Solution
A welding gun control device that moves the movable electrode at a first speed and the counter electrode or welding target at a second speed lower than the first speed, using a motion controller and detector to minimize load and vibration, and maintain the welding gun's path alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the movable electrode moves at high speed to detect the workpiece, then detection speed is improved, but the load applied to the workpiece increases causing deformation
Solution Approach 1:
The detection process is segmented into two phases: a high-speed approach phase where the movable electrode quickly approaches the workpiece, and a low-speed contact phase where the electrode slowly contacts the workpiece for precise detection. This segmentation allows the system to achieve fast detection overall while minimizing the load applied during the critical contact moment.
Solution Approach 2:
The movable electrode performs a preliminary high-speed approach to get close to the workpiece before making contact. This preliminary action allows the electrode to cover most of the distance quickly, then switch to a slow, controlled movement for the final contact, reducing the load on the workpiece during detection.
2Manufacturing precision
If the counter electrode is moved to the contact position after detection, then positioning accuracy is improved, but vibration of the welding gun increases
Solution Approach 1:
The system dynamically adjusts the movement speeds of both electrodes based on the detection phase. During detection, the movable electrode moves slowly to minimize vibration. After contact is detected, the counter electrode is moved to the contact position while the movable electrode remains stationary or moves minimally, maintaining positioning accuracy while controlling vibration throughout the process.
3Productivity
If the movable electrode moves quickly to detect the workpiece, then productivity is improved, but the actual path deviates from the instructed path
Solution Approach 1:
The movement process is segmented into a fast approach phase and a slow detection phase. During the fast approach, the movable electrode moves quickly toward the workpiece along the instructed path. Upon nearing the detection zone, it transitions to slow movement for precise detection, ensuring path alignment is maintained while maximizing detection efficiency.
Solution Approach 2:
The system continuously monitors the position and operating status of the servomotor driving the movable electrode. This feedback allows the control device to adjust the movement speed in real-time, maintaining accurate path alignment during the slow detection phase while having previously covered distance efficiently during the fast approach phase.
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
Reduces the load on the workpiece during detection, minimizes vibration of the welding gun, and prevents path deviation, thereby improving weld quality and alignment.
Implementation Method 1
a current or torque of a servomotor of a welding gun is monitored. When a change tendency of the current or torque of the servomotor varies, it is determined that a movable electrode makes contact with or is completely separated from a workpiece
Data Source
AI summary
Provided is a welding gun control device whereby it is possible to reduce a load placed on a workpiece during workpiece detection in spot welding. This welding gun control device for controlling a welding gun for pressing an object to be welded between a movable electrode driven by a servomotor and a counter electrode facing the movable electrode and performing welding comprises: an operation control unit for causing the movable electrode to move at a first speed in a state in which the object to be welded is disposed between the movable electrode and the counter electrode, and causing the counter electrode or the object to be welded to move at a second speed slower than the first speed; and a workpiece detection unit for detecting the object to be welded on the basis of the operating state of the servomotor for driving the movable electrode, while the movable electrode and the counter electrode are caused to move by the operation control unit.