Spot Welding Electrode Angle Correction to Prevent LME Cracking
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Solution Overview
Problem
Resistance spot welding machines face challenges in suppressing Liquid Metal Embrittlement (LME) cracking when welding galvanized high tensile strength steel sheets, particularly due to electrode tip tilt angles and the compactness of electrodes, which existing technologies do not adequately address.
Innovation Solution
A resistance spot welding machine equipped with a pair of electrodes featuring an angle correction mechanism using universal joints with convex and concave spherical shapes, allowing for tilt angle correction and enabling the electrodes to apply current while maintaining a compact design, thus preventing LME cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flanged rod is used to correct tilt angle by oscillation, then LME cracking is suppressed, but the electrode tip shifts relative to the steel sheets causing LME cracking
Solution Approach 1:
The invention employs a spherical surface at the contact point between the flanged rod and base member, enabling multi-directional oscillation of the electrode tip. This spherical geometry allows the electrode to correct tilt angles in any direction while maintaining contact with the steel sheets, preventing both LME cracking and position shift by distributing the correction motion across multiple degrees of freedom
2Ease of manufacture
If wire is placed outside the electrode shanks to supply current, then current supply is simplified, but the wire hinders welding of narrow parts
Solution Approach 1:
The invention integrates the current supply function directly into the electrode shank structure by making the shank itself conductive. This merging of the structural and electrical functions eliminates the need for separate external wiring, allowing the electrode to access narrow welding areas without obstruction while maintaining reliable current supply through the integrated conductive shank
3Reliability
If electrode structure is made complex to correct tilt angles, then LME cracking is suppressed, but electrode compactness is reduced
Solution Approach 1:
The invention uses a flexible connection between the flanged rod and electrode shank that allows controlled oscillation and tilt correction. This flexible mechanism enables the electrode to adapt to tilted steel sheets and suppress LME cracking through natural elastic deformation rather than rigid mechanical linkages, maintaining a relatively simple and compact overall structure while achieving the desired angle correction functionality
Data Source
AI summary
A resistance spot welding machine contains a pair of electrodes each having an electrode tip to sandwich a plurality of steel sheets; and an angle correction mechanism that is provided in at least one of the pair of electrodes and that is capable of correcting the angle of the electrode tip to the steel sheets. The resistance spot welding machine spot welds the plurality of steel sheets by sandwiching the plurality of steel sheets with the pair of electrode tips and applying current while a welding force is applied to the pair of electrode tips, and the angle correction mechanism has a pair of universal joints each having an engaging portion having an end with a convex spherical shape and an engaged portion having a concave spherical shape to which the engaging portion fits slidably.