Spot Welding Gun Abnormality Detection via Servomotor Position Deviation
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Solution Overview
Problem
Spot welding systems face challenges in detecting abnormalities such as deformation or crack in the arm of the spot welding gun and changes in friction within the mechanical unit, leading to potential weld quality degradation and increased maintenance costs due to the need for frequent visual inspections and pressure sensor calibration.
Innovation Solution
A spot welding system that includes an encoder to measure the rotational position of the servomotor, a unit to calculate elastic displacement quantity deviations, and an estimating unit to detect abnormalities based on these deviations, allowing for quick identification of issues and automatic correction of welding pressure, thereby reducing the need for frequent shutdowns and visual inspections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If visual inspection is performed to detect arm deformation or cracks, then abnormality detection is possible, but it takes time and requires operator expertise
Solution Approach 1:
The patent replaces manual visual inspection with an automated measurement system that uses a sensor to detect the position of the electrode tip. This mechanical/electrical substitution eliminates the need for operator visual inspection, reducing both time loss and improving detection reliability through objective numerical measurements.
Solution Approach 2:
The system enables self-diagnosis by automatically measuring electrode tip position and comparing it against reference values stored in memory. The spot welding gun performs its own abnormality detection without external inspection, identifying arm deformation or cracks through automated position deviation analysis.
2Measurement precision
If pressure sensor calibration is performed to detect welding pressure deviations, then accurate pressure measurement is achieved, but the system must be shut down and calibration is expensive
Solution Approach 1:
The patent introduces an intermediary measurement approach by using electrode tip position as a proxy indicator for welding pressure conditions. Instead of directly measuring pressure with expensive sensors, the system measures the position of the electrode tip, which correlates with pressure deviations caused by arm deformation or mechanical unit friction changes.
Solution Approach 2:
The system replaces expensive pressure sensor calibration with a mechanical position measurement approach. By measuring electrode tip position using a position sensor and comparing it to reference positions, the system detects welding pressure deviations without requiring costly pressure sensors or system shutdowns for calibration.
3Productivity
If the spot welding gun continues operation without inspection, then productivity is maintained, but weld quality degrades due to undetected abnormalities
Solution Approach 1:
The patent implements continuous feedback by automatically measuring electrode tip position during operation, comparing it against reference values, and providing real-time abnormality detection. This feedback mechanism allows the system to maintain productivity while ensuring weld quality through continuous monitoring that alerts operators to abnormalities without requiring production shutdowns.
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
Enables rapid estimation and correction of welding pressure deviations, improving weld quality by reducing false detection of abnormalities and eliminating the need for frequent visual inspections and additional measurement equipment, thus lowering maintenance costs and increasing operational efficiency.
Implementation Method 1
an encoder measuring a rotational position of the servomotor
Implementation Method 2
an elastic displacement quantity deviation calculating unit calculating, as an elastic displacement quantity deviation in the spot welding gun, a rotational position deviation between a rotational position of the servomotor when the servomotor is driven in accordance with the reference welding pressure command value and a rotational position of the servomotor when the servomotor is driven in accordance with the at least one detective welding pressure command value
Data Source
AI summary
A spot welding system (1) includes a welding pressure command generating unit (31) which generates a reference welding pressure command for a spot welding gun by applying pressure to workpieces to be welded between two electrode tips and at least one detective welding pressure command, an elastic displacement quantity deviation calculating unit (32) calculating, as an elastic displacement quantity deviation, a rotational position deviation between the rotational position of a servomotor when the reference welding pressure command is used and the rotational position of the servomotor when at least one detective welding pressure command is used, and an estimating unit (34) which estimates that there is an abnormality in the spot welding gun when the deviation between the elastic displacement quantity deviation based on the reference welding pressure command and at least one detective welding pressure command and the reference displacement quantity deviation is greater than a predetermined value.