Keeping electrodes in tip-top shape
Resistance spot welding (RSW) is extensively employed in high-volume automotive production. As manufacturers have increasingly turned to light-weight aluminium, RSW has become cost prohibitive for mass production. Aluminium reacts quite aggressively with the consumable copper electrode tips on RSW guns. Poor maintenance leads to inferior weld quality and subsequent frequent work stoppages, imposing increased maintenance costs and lost revenue. For the numerous small and medium-sized enterprises (SMEs) in the field, these issues further impinge on market competitiveness in the face of increasing competition from low-labour–cost countries. EU-funded scientists developed an automated adaptive control system to monitor, optimise and maintain electrode tip quality with the project 'Adaptive tip dress control for automated resistance spot welding' (SMARTDRESS). It senses tip wear, initiates tip repair (via tip dressing) and automatically optimises the tip dressing schedule. The SMARTDRESS technology will not only improve weld quality and minimise line stoppages, it will enable cost-competitive spot welding of lightweight aluminium. The SMARTDRESS system uses an optical sensor to monitor the condition of the RSW electrode tips. The control system determines if maintenance is required, sparing unnecessary scheduled maintenance that expends time, money and electrode material. Tip dressing is a process of removing uneven material from the tip face to repair any damage. The tip is thus returned to its original geometry but material is lost. SMARTDRESS also exploits a special abrasive dressing that lightly cleans the electrodes without cutting away valuable copper. Patents have been filed for both the optical sensor and the control technology. Electrode maintenance issues remain the main reason for work stoppages in automotive body manufacturing. The SMARTDRESS abrasive dressing technology for electrode tip monitoring and repair offers currently unavailable capabilities. These advances promise important enhancements in weld quality and overall productivity that will significantly improve the competitive position of the numerous SMEs in the automotive manufacturing sector.
Keywords
Automotive, resistance spot welding, weld quality, electrode tip, tip dress
