# Advancing Defect Detection in Laser Welding: A Machine Learning Approach Based on Spatter Feature Analysis

## TL;DR

This paper introduces a machine learning framework using infrared thermography to detect defects in laser welding, achieving high accuracy in real-time.

## Contribution

A novel sensor-driven framework using IR thermography and deep learning for real-time defect detection in laser welding is proposed.

## Key findings

- A hybrid CNN–transformer model achieves a mean Average Precision of 0.85 for defect detection in laser welding.
- Infrared thermography-based spatter dynamics provide actionable sensing signatures for automated defect prediction.
- The framework enables near-real-time inference on a CPU, suitable for industrial closed-loop quality control.

## Abstract

Full-penetration laser welding (FPLW) is increasingly adopted in manufacturing pipelines, yet its industrial scalability is constrained by in-process defect formation, particularly incomplete penetration. To address this, we propose a sensor-driven framework for non-destructive monitoring and automated defect detection that uses infrared (IR) thermography as the primary in situ sensing modality and applies deep learning to the acquired thermal signals. High-speed IR camera recordings were processed to track spatter and the weld zone, yielding a time series of physically interpretable spatiotemporal features (mean spatter area, mean spatter temperature, number of spatters, and mean welding zone temperature). Defect recognition is formulated as a multi-label classification problem targeting incomplete penetration, sagging, shrinkage groove, and linear misalignment, and multiple temporal models were evaluated on the same sensor-derived feature sequences. Experimental validation on 09G2S pipeline steel demonstrates that the proposed time series pipeline based on a hybrid CNN–transformer achieves a mean Average Precision (mAP) of 0.85 while preserving near-real-time inference on a CPU. The results indicate that IR thermography-based spatter dynamics provide actionable sensing signatures for automated defect prediction and can serve as a foundation for closed-loop quality control in industrial laser pipeline welding.