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How to Achieve Firm, Non-Detachable Welds for Stud Projection Welding on Capacitor Discharge Spot Welders
Jul 10,2026
Capacitor discharge projection welding is widely adopted for stud welding in hardware, home appliances and auto structural parts, featuring minimal deformation and narrow heat-affected zones. However, loose or detached studs frequently appear in mass production. Below are defect types, root causes and corresponding solutions.
I. Common Detachment Defects
1.No effective fusion between stud and sheet, only superficial contact; studs can be twisted off, usually caused by improper parameters.
2.Weld surface appears normal but the internal fusion layer is loose, prone to detachment under vibration or load.
3.Unilateral fusion & eccentric nuggets with tilted studs and black spots; tearing and detachment under stress.
II. Root Causes of Weld Detachment
1.Warped sheets, misplaced studs, dirty surfaces and positioning deviations create welding gaps, leading to arcing and pseudo-welds.
2.Insufficient pressure fails full compaction with shallow fusion; excessive pressure flattens stud projections, dispersing heat and reducing joint strength.
3.Insufficient energy forms tiny weak nuggets; excessive energy embrittles welds susceptible to later fracture under vibration.
4.Instant rapid discharge cannot fully vent molten pool gas, leaving internal micro-pores and loose weld structures prone to tearing.
5.Oil, dust and oxide films form isolating layers to block complete metal fusion, generating pseudo-welds and interlayer defects.
6.Worn, carbon-deposited or eccentric electrodes cause uneven current & force distribution, resulting in incomplete nuggets and unstable welding strength.
7.Deformed studs with large burrs produce irregular nugget formation.
8.Heat buildup from continuous welding loosens nugget structure and lowers joint strength.
III. Process Methods for Solid Welds
1.Match parameters rationally: Deliver even heat penetration and exhaust pores. Combine pre-press, constant pressure & hold stages according to sheet thickness to eliminate gaps and reduce pseudo-welds.
2.Thorough pre-weld cleaning: Remove oil, dust and oxide contaminants; lightly polish heavily oxidized areas to avoid isolating impurities causing false fusion.
3.Standard electrode maintenance: Grind electrodes daily to keep flat, concentric and clean; replace worn unqualified electrodes timely.
4.Optimize fixture positioning & support: Apply solid rigid support at welding positions, no suspended welding. Use dedicated jigs to hold studs vertically; calibrate fixtures regularly to prevent positioning offset.
5.Control incoming stud quality: Use intact studs without deformation or burrs.
6.Stabilize thermal field & operation: Maintain unblocked electrode water cooling; add cooling pauses between continuous welds to avoid loose nuggets from heat accumulation.
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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