Use of modified electrode caps for surface quality welds in resistance spot welding

Surface quality of resistance spot welds is important in many applications. The surface quality of welds made with a modified electrode cap on the face side of the weld was investigated and compared with welds made using a copper backing bar and standard electrode caps. The surface features of the spot welds were evaluated and compared using laser surface scanning technology. The results indicate that the welds made with the modified electrode caps are equivalent to the welds made using copper backing bars in regards to the surface quality. The weld lobes were determined for resistance spot welding using combinations of standard electrode caps, an Asian T-16-D type, and the modified electrode caps T-16-D-10 plus the T-16-D type, on the face and bottom side of the weld. The weld lobes made using the latter combination of caps are shifted towards higher currents compared to those welded with standard electrode caps. Metallographic examination was carried out to compare the weld nugget sizes and locations within the welded steel sheets for various welding parameters. Use of the modified electrode caps instead of the copper backing bars can increase flexibility of the welding process and significantly reduce cost of the fixtures utilised in the production lines.