Automated resistance spot welding in automotive production use robot mounted welding guns, which apply welds using copper alloy

Tip dresser� systems attempt to maintain the electrode tip quality during production

Project Background

The automotive sector currently produces around 60 million vehicles per annum, relying heavily on the Resistance Spot Welding (RSW) joining process for manufacturing the body-in-white (BIW) - the primary stage of vehicle body construction. For this, production lines utilise RSW guns to apply the welds, each using consumable electrodes ('tips') to contact the work pieces and transmit current to make the weld. These tips are the most important component in a spot welding system, and their degradation which occurs during welding (coated) steel vehicles rapidly leads to sub-standard weld quality (which in turn causes expensive line stoppages).

Tip dresser’ systems are commonly utilised on production lines in an attempt to maintain the quality of the tips. However, current systems require manual set-up, optimisation and continued monitoring during production. This cannot be reliably or consistently performed for large production lines, and feedback from weld engineers responsible for RSW systems consistently states that poor electrode tip dressing is the primary cause of spot weld quality problems and associated production stoppages in BIW. With a vehicle typically rolling off a production line every 1-2 minutes; a tip dress issue causing even a 5 min line stoppage once per day can result in a loss of 10 vehicles per week; equating to ~7M of lost revenue per annum for an average 15k vehicle production line.

In addition, present tip dress systems cannot be applied successfully to high volume production of aluminium assemblies, preventing the application of RSW; and forcing the use of higher cost technologies - primarily self-pierced riveting. The result is a typical on-cost of 90 per vehicle from the use of rivets, equating to 25M over the life of a typical product.

The SmartDress project has developed an adaptive, tip-dressing system able to automatically monitor and optimise electrode tip quality in resistance spot welding.