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How to Judge and Improve the Phenomenon of Uneven Nugget in Multi‑Point Projection‑Welding of Stainless‑Steel Sheet Parts
Sep 05,2026
Multi‑point projection‑welding of stainless‑steel sheets is widely adopted in household‑appliance and auto‑parts industries. By one‑time energizing and pressurizing, multiple projection points finish welding simultaneously. The core quality indicator is the uniformity of each weld nugget. Uneven nugget means inconsistent nugget size and penetration depth among multiple welding points. Partial points have insufficient fusion while partial points are over‑welded, which will cause unstable overall connection strength and partial point‑fall‑off risk in service.
I Main Manifestations of Uneven Weld Nugget
1.Obvious difference in nugget size: some nuggets are large and full, while some are tiny or even invisible.
2.Difference in penetration depth: partial points show deep penetration, partial points have shallow penetration with insufficient fusion.
3.Partial over‑burning: individual points have over‑burning surface, indentation is too deep, and base‑material is excessively softened.
II Root Causes for Uneven Nugget in Multi‑Point Projection‑Welding
1.Unreasonable projection‑point design: inconsistent height, size and shape of each projection point. Some projections are too high and will contact first and bear most pressure and heat; low projections cannot obtain enough energy, resulting in insufficient fusion.
2.Poor flatness of workpiece itself: stainless‑steel sheets are warped or deformed; during clamping, partial projection points cannot make effective contact.
3.Insufficient parallelism of upper‑lower electrodes: electrode faces are not parallel. Pressure distribution on each projection point is chaotic, leading to big difference in nugget forming.
4.Unreasonable pressure‑applying logic: pressure rises too fast. High pressure crushes high projections at the initial stage, and the remaining low projections cannot be fully contacted.
5.Wear and contamination of electrode surface: electrode surface is worn, dented or adhered with metal sundries, causing unstable current conduction on partial welding positions.
6.Too‑large quantity of simultaneous‑welding projection points: equipment power capacity is limited. Excessive projection points lead to dispersed energy; each point cannot obtain enough welding energy.
III Improvement Solutions
1.Optimize projection‑point design: unify the height, size and shape of all projection points of workpieces. Ensure each projection has consistent stress‑bearing condition during welding.
2.Control workpiece flatness: straighten and shape stainless‑steel‑sheet workpieces before welding, eliminate warping and bending deformation.
3.Calibrate electrode parallelism: regularly calibrate the parallelism of upper‑lower electrode working faces, avoid inclined stress.
4.Optimize pressure‑applying curve: adopt segmented slow‑rising pressure. Make all projection points contact and bear pressure evenly before energizing, so as to balance pressure distribution of each point.
5.Maintain electrodes regularly: dress and clean electrode working faces, remove surface denting and metal adhesion, guarantee stable and consistent current conduction.
6.Reasonably control the quantity of simultaneous‑welding points: do not exceed the rated power range of welding equipment. If there are too many projection points, adopt multi‑time segmented welding.
Wuxi Haifei Intelligent Equipment Co., Ltd. https://www.haifeiwelder.com/
Wuxi Haifei Intelligent Equipment Co., Ltd. has been focusing on the R&D and production of spot‑welding machines for 17 years. The company has obtained ISO9001 Quality Management System Certification, China Compulsory Certification (3C) and CE Certification. It is a National High‑tech Enterprise, a Specialized, Refined, Differential and Innovative Enterprise of Jiangsu Province, a Specialized, Refined, Differential and Innovative Enterprise of Wuxi, and a Gazelle Enterprise in the Southern Jiangsu National Self‑Dependent Innovation Demonstration Zone.
Should you be interested in our spot‑welding machines, please contact us: 400‑0510‑750
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Wuxi HAIFEI Intelligent Equipment Co., Ltd.
Wuxi HAIFEI Welding Equipment Co., Ltd.
Add: 28 Shuiyun Road, Yuecheng, Jiangyin, Jiangsu Province, China. (Postal Code: 214404)
Mobile: +86 18915302352
Email: wushijie@jshaifei.com