Three distance method and its experimental verification for electrode displacement measurement in resistance spot welding

For the traditional measurement methods including the upper electrode movement and long arm tooling in resistance spot welding, there are errors in measuring electrode displacement, which introduced by the deformation of welding torches caused by the welding thermal expansion force during resistance spot welding process. Therefore, the trapezoidal relationship measurement method and three distance measurement method were suggested, and their accumulative calculation errors were analyzed and compared. Then, the three distance measurement method with less errors was experimentally verified through using the inverted F type tooling and experimental monitoring and verification system for electrode displacement measurement using laser displacement sensors and data acquisition system of embedded industrial control computer with LabVIEW programming. The results showed that it is correct and feasible, and the deformation displacement of lower electrode of the C type welding torches is not the neglectful part of the electrode displacement introduced by the dynamic electrode force.