Department of Electronic Engineering, Campus de Burjassot, Universidad de Valencia, 46100 Valencia, Spain.
Ford Spain, Poligono Industrial Ford S/N, 46440 Almussafes, Spain.
Sensors (Basel). 2023 Jan 12;23(2):894. doi: 10.3390/s23020894.
Wear of the secondary of the welding gun, caused by mechanical fatigue or due to a bad parameterization of the welding points, causes an increase in quality problems such as non-existent welds or a reduced weld nugget size. In addition to quality problems, this defect causes production stoppages that affect the final cost of the manufactured part. Different studies have focused on evaluating the importance of different welding parameters, such as current, in the final quality of the welding nugget. However, few studies have focused on preventing weld command parameters from degrading or changing. This investigation seeks to determine the wear of the secondary circuit to avoid variability in the current supplied to the welding point caused by this defect and the increase in circuit resistance, especially in industrial environments. In this work, a virtual sensor is developed to estimate the resistance of the welding arm based on previous research, which has shown the possibility of detecting secondary wear by analysing the duty cycle of the power circuit. From the data of the virtual sensor, an anomaly detection method based on the Mahalanobis distance is developed. Finally, an integral system for detecting secondary wear of welding guns in real production lines is presented. This system establishes performance thresholds based on the analysis of the Mahalanobis distance distribution, allowing monitoring of the secondary circuit wear condition after each welding cycle. The results obtained show how the system can detect incipient wear in welding guns, regardless of which part of the secondary the wear occurs, improving decision-making and reducing quality problems.
焊接枪副的磨损，由机械疲劳或由于焊点参数设置不当引起，会导致质量问题增加，如不存在焊缝或焊接熔核尺寸减小。除了质量问题，这种缺陷还会导致生产停止，影响制造零件的最终成本。不同的研究集中在评估不同的焊接参数（如电流）对焊接熔核最终质量的重要性。然而，很少有研究关注防止焊接命令参数降级或变化。这项研究旨在确定二次电路的磨损情况，以避免由于这种缺陷和电路电阻增加而导致的焊接点电流供应的可变性，特别是在工业环境中。在这项工作中，开发了一种基于先前研究的虚拟传感器来估计焊接臂的电阻，该研究表明通过分析功率电路的占空比来检测二次磨损的可能性。从虚拟传感器的数据中，开发了一种基于马氏距离的异常检测方法。最后，提出了一种用于在实际生产线中检测焊接枪二次磨损的集成系统。该系统基于马氏距离分布的分析建立了性能阈值，允许在每个焊接周期后监测二次电路磨损情况。所得结果表明，该系统如何能够检测焊接枪的初始磨损，而不管磨损发生在二次的哪个部分，从而改善决策并减少质量问题。
