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What factors are usually related to insufficient nut torque in nuts welded by energy storage spot welders?
Nov 10,2026
When energy storage spot welders weld flange nuts to sheet metal parts, insufficient nut torque is a common quality problem. Insufficient torque means the nugget strength is insufficient, and the nut is prone to loosening or falling off during assembly or use.
I. Incoming material and workpiece surface factors
1. Insufficient height of nut projections, irregular shape, or too few projections result in a small nugget volume after melting and insufficient bonding strength.
2. Oil stains, rust, oxide layers, or abnormal coatings on the sheet surface make contact resistance unstable, heat distribution uneven, and nugget formation insufficient.
3. Improper matching of nut and sheet materials, or impurities and hidden defects in incoming nuts, result in low bonding strength after welding.
4. Large sheet thickness tolerances and poor consistency between incoming batches cause some products to have smaller nuggets under the same parameters.
II. Capacitor and energy output factors
1. Decreased capacitor capacity and increased internal resistance reduce the total energy released, the nut projections are not fully melted, the nugget is small, and torque is insufficient.
2. Uneven aging of capacitors in the same group causes large fluctuations in discharge energy each time, weld strength fluctuates, and torque is unstable.
3. Low charging voltage setting or energy not matched to nut specifications results in insufficient heat input and incomplete melting of projections.
4. Poor contact in the welding circuit and oxidized cable joints result in lower actual energy output to the weld spot.
III. Electrode and tooling status factors
1. Worn electrode end faces, slag adhesion, and buildup increase contact resistance, reduce current density, and result in smaller nuggets.
2. Poor electrode alignment or uneven end faces cause uneven pressure and current distribution and insufficient local fusion.
3. Worn locating pins and loose tooling cause eccentric or tilted nut positioning, poor contact between projections and sheet, and false welds.
4. Insufficient electrode pressure prevents the projections and sheet from being pressed firmly, contact resistance is too high, heat is concentrated but the nugget is loose.
IV. Welding parameters and timing factors
1. Low welding current and short conduction time result in insufficient heat input and incomplete melting of projections.
2. Insufficient pre-pressure time means the projections and sheet are not compacted before energization, and the contact state is unstable.
3. Insufficient hold time or premature pressure release causes the nugget to lose pressure before cooling and setting, and strength decreases.
4. Parameters are not adjusted according to nut specifications and sheet thickness, and old parameters are still used after changeover.
Wuxi Haifei Intelligent Equipment Co., Ltd. official website: https://www.haifeiwelder.com/
Wuxi Haifei Intelligent Equipment Co., Ltd. has been dedicated to the research and production of energy-storage spot welding machines for 17 years. The company has passed the ISO9001 quality management system certification, the national 3C certification and the CE certification. It is a national high-tech enterprise, a Specialized, Refined, Distinctive and Innovative enterprise of Jiangsu Province, a Specialized, Refined, Distinctive and Innovative enterprise of Wuxi City, and a Gazelle enterprise of the Southern Jiangsu National Independent Innovation Demonstration Zone. If you are interested in our energy-storage spot welding machines, please contact us at liuyiyu@jshaifei.com
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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