A thermographic visual inspection system for crack detection in metal parts exploiting a robotic workcell

• Thermography was explored as a means for the detection of micro defects.
• We developed a system capable of finding cracks in metal parts using thermography.
• The system is very robust thanks to the complete knowledge of the imaging process.
• The system is able to deal with parts of very complex geometry.
• The proposed inspection method is cleaner than other alternatives currently in use, and does not use polluting substances.

Cracks are the main source of failure in the production of metal parts: systems for checking their presence are therefore crucial for defect-free production. In this paper, an autonomous system for performing this quality control is presented. The system is equipped with a heating tool, a thermocamera, and a robot to handle the part. The inspection process is based on the observation of the propagation of thermal waves through the inspected part, a method that can highlight very small cracks with high reliability. A knowledge-based approach to visual inspection is exploited for detecting the cracks: all the system parameters are known by means of an accurate calibration of the workcell. The system was tested on a large dataset and demonstrated its capability of detecting tiny production defects, that can lead to dangerous failures when the metal components are put under strong mechanical stress.