Dada acquisition and defects analysis in resistance spot welding process based on parallel port

An efficient data acquisition system was built to collect welding parameter of aluminum alloys shock wave resistance spot welding by using single chip processor and process computer. The communication port of the sy stem between single chip processor and process computer is parallel port.This system have many advanlages such as better anti-jamming performance, high reliability, better expansion capacity, fast picking rate and transfer rate.The software of this system developed by LabVIEW has functions such as communication, data manipulation, the database and the data analysis function.A systematic analysis based on acquisition data shows that the earlier splash can be identified by " collapsing abrupt change" of tip voltage signal and " high frequency restlessness abrupt change" of electrode force signal, but for later splash, it can be identified only by " high frequency restlessness abrupt change" of electrode force signal.Moreover the incomplete fusion can be identified by " thermal expansion rise value" and "forging force drop value" extracting from electrode displacement.