Worldwide First Automated and Contactless Spot Weld Inspection System for In-Line
In spite of the sheets of cars being welded by fully robotized cells, the inspection of spot welds is still conducted manually out of the line with a handheld ultrasound device. Only 1.5% of approx. 5000 spot welds in a car are tested at present. About 25 seconds are needed to test one spot weld resulting in testing costs of about 0.5€ per spot weld. Although attempts have been made by several car manufacturers and producers of testing equipment, the testing procedure could not be automated. The needed coupling gel as well as the high alignment accuracy (tolerance of 30μm) for a reliable measurement have prevented today’s technology from being automated. In addition, manual ultrasonic testing results are very operator dependent due to difficulties in probe positioning, irregular surfaces and difficulties in interpreting the results.
AutoSpot aims to develop, test, deploy and validate the first contact-free and fully automated in-line spot weld inspection solution. Such innovation will address four goals:
- Reduction of time to test one spot weld by a factor of 3 down to approximately 8 seconds (instead of 25 seconds; this would also facilitate an increase of testing)
- Reduction of testing costs by a factor of 10 thanks to automation (from 0.47 €/weld to 0.04 €/weld)
- Higher repeatability and accuracy thanks to automation (no human error)
- Optimized welding through closed-loop feedback and early detection and correction of defects In order to reach these goals, the project focuses on:
- a novel non-destructive testing method generating an acoustic shock wave inside a car body with a laser and listening to the resulting airborne ultrasound with an optical microphone to identify spot welds that do not meet required quality criteria,
- calibration data for a wide range of thicknesses, materials and geometries, and
- factory-ready communications software and user interface.