Optical sensor improves spot welding process
Spot welding is a pivotal joining technology in many industry segments, but despite its maturity the technology still can be improved. In particular in automotive manufacturing, the quality of spot welding greatly impacts the productivity. Though the welding process is considered robust and efficient, the electrodes wear relatively rapidly leading to uneven quality of the welding spots and thus the electrode tips need to be redressed or reworked. This derating is particularly pronounced in welding aluminium components.
Frequent downtimes due to maintenance intervals and unnecessary consumption of copper electrodes can be reduced by automatizing the electrode adjustment. For this purpose, Fraunhofer IPMS developed an optical sensor which records the condition of the welding electrode and thereby calculates the time and extent of cleaning or mechanical post processing required. The system monitors both welding electrodes simultaneously from various perspectives. The electrodes are lit by diffuse monochrome LED lighting generated by opal glass. The light is sent to the electrode via a mirror arrangement and beam splitter and then back to the photo detector. Lighting and image recording thus use the same optical elements. The first prototype is based on a passive camera system which is controlled by an external computer via a USB interface. Later, the control is to be integrated into the sensor system. The first tests under live production conditions are scheduled to take place during the current year.
The development of the sensor was part of the SmartDress project which aimed at devising a recently was concluded successfully fully automated adaptive control system that optimises, monitors and maintains electrode tip quality in RSW (Resistance spot welding) applications. Besides Fraunhofer IMPS two research institutes and four commercial companies participated in the project which has been funded by the EC under Framework 7. The research institutes are Finland’s VTT and Great Bitain’s TWI which was responsible for the technical performance of the resistance spot. The commercial companies were Sinterleghe srl, Fisher-Smith, Finaids and software vendor Swantec.
For more information on the SmartDress project, visit https://www.smartdress-project.eu
Read also:
3D weld seam inspection camera and software
TACO project yields MEMS-based robotic eyes capable of 3D scanning
Finnish start-up automates optical inspection for highly reflective objects
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