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What Hidden Risks Arise When Nuts Whose Threads Contain Impurities or Burrs Are Welded on a Flexible Projection Welding Workstation?
Nov 07,2026
When a flexible projection welding workstation welds nuts to sheet-metal brackets, impurities and burrs left in the threads look like a minor incoming-material issue, but in practice they trigger a series of hidden risks during welding and in use.
I. Thread Damage and Failure of Go/No-Go Gauges
1. Burrs and iron chips adhere to the thread profile under heat and pressure, causing local deformation and an incomplete thread form.
2. Impurities carbonise and embed in the threads, so the go gauge jams and the no-go gauge behaves abnormally; burrs form hard spots after cooling and easily cause seizure and thread stripping during assembly.
II. Poor Fit and Nugget Defects
1. Impurities sit between the nut and the sheet-metal mating surface, so the projections contact the sheet insufficiently and local gaps form.
2. Contact resistance is uneven, the nugget is undersized or fusion is incomplete, resulting in cold welds; impurities decompose under heat and generate gas, forming pores and slag inclusions.
III. Spatter and Locating Offset
1. Impurities vaporise and burst at high temperature, producing spatter that contaminates the area around the weld spot and the electrode surface.
2. The nut is not seated properly or is tilted, so the force is offset and the weld deviates; spatter residue falls into the threads or locating slots, worsening locating accuracy and causing blockage.
IV. Electrode and Tooling Wear
1. Spatter and impurities adhere to the electrode end face, causing slag pickup and build-up and faster wear.
2. Nut offset subjects the electrode to lateral eccentric load and one-sided wear; impurities fall into locating pins and slots, accelerating wear of the locating parts.
V. Assembly and Service Risks
1. Impurities and hard spots make bolt insertion difficult, with torque below specification or thread stripping; nuts with damaged threads give insufficient connection strength after assembly and carry a risk of loosening.
2. Hidden defects are hard to detect in outgoing inspection, and rework costs are high once they reach the assembly line.
VI. Prevention and Improvement Measures
1. Incoming control: add thread sampling inspection when nuts enter the plant, checking impurities, burrs and go/no-go gauge status.
2. Pre-weld cleaning: blow air or brush the threaded holes before loading.
3. Tooling protection: the locating pin extends into the nut bore for location and blocks spatter; clean the locating slot regularly.
4. In-process inspection: perform first-piece go/no-go gauge and torque verification before mass production, and sample at set intervals during the process.
5. Electrode and tooling maintenance: keep the electrode end face flat and clean, dress or replace it regularly, and replace worn locating parts in time.
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 flexible projection welding workstations 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 flexible projection welding workstations, please contact us: 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