1) pre-pressing stage -- the electrode drops to the current connection stage to ensure that the electrode presses the workpiece and there is appropriate pressure between the workpiece. 

2) welding time -- the welding current passes through the workpiece and generates heat to form the core.

3) maintenance time -- the welding current is cut off and the electrode pressure continues to maintain until the nugget solidifies to sufficient strength. 

4) rest time -- the electrode begins to lift until the electrode begins to drop again, starting the next welding cycle