Steel Sheet Gap Detection in Resistance Spot Welding
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Solution Overview
Problem
Existing resistance spot welding methods fail to reliably determine the presence of gaps between steel sheets due to indirect measurement of strain gauges, which can be affected by electrode wear and surface roughness, leading to potential strain in welded parts.
Innovation Solution
A method and device using a range finder to measure distances on the primary surfaces of steel sheets before welding, calculating regression lines to determine the angle between these surfaces, allowing direct detection of gaps and ensuring reliable gap detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If strain gauges are used to indirectly measure gap through electrode deformation, then measurement can be performed during pressurization, but the measurement precision deteriorates due to electrode wear and surface roughness affecting the strain gauge readings
Solution Approach 1:
The patent replaces the mechanical strain gauge measurement system with an optical measurement system. A laser displacement sensor optically measures the position of the steel sheet surface before and during pressurization, calculating gap based on displacement rather than mechanical strain. This eliminates the influence of electrode wear and surface roughness on measurement accuracy, as the optical sensor measures directly from the steel sheet surface without contact with electrodes.
2Manufacturing precision
If the driving angle is adjusted to compensate for disturbances, then welding quality improves, but the complexity of the welding system increases due to additional measurement and control mechanisms
Solution Approach 1:
The patent performs preliminary measurement of the steel sheet surface position before pressurization using a laser displacement sensor. This preliminary action captures the initial state of the steel sheets, allowing calculation of the driving angle and prediction of gap formation. By measuring beforehand rather than during welding, the system avoids complex real-time measurement mechanisms while still achieving accurate gap control and high welding quality.
3Ease of manufacture
If gap is not detected and compensated, then welding process remains simple, but harmful factors increase due to cavity formation and strain in welded parts
Solution Approach 1:
The patent introduces a laser displacement sensor as an intermediary measurement device that non-contactly measures the steel sheet surface position. This intermediary provides accurate gap prediction information without complicating the welding process itself. The measured displacement data is used to calculate expected gap and adjust welding parameters, thereby preventing cavity formation and strain damage while maintaining process simplicity through external measurement rather than integrated complexity.
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 accurate determination of gaps between steel sheets, reducing the risk of strain in welded parts by directly measuring surface shapes, thereby improving welding quality.
Implementation Method 1
a range finder 35 measures distances to a plurality of points on the primary surface
Data Source
AI summary
A method for determining a gap between steel sheets in resistance spot welding by directly measuring the shapes of the primary surfaces of the steel sheets in a state after the steel sheets are pressurized with first and second electrodes and before welding current is applied between the electrodes. The method includes: a distance measurement step of measuring, in a state after a plurality of overlapped steel sheets is pressurized and before welding current is applied between the first and second electrodes, the distances to a plurality of points on a primary surface of an electrode-vicinity region of the uppermost or lowermost steel sheet and the distances to a plurality of points on a primary surface of a separation region of the steel sheet with a range finder; and a determination step of determining whether a gap is present between the overlapped steel sheets based on the measured distances.