Reproducing Good Quality Spot Welds
A good quality spot weld usually follows a
classical dynamic resistance curve as shown to the left
(yellow line). When welding current is
applied (as shown in the red line), the resistance
across the electrodes will typically show an increasing
resistance. This will peak at the point where the molten
metal of the weld nugget will allow the penetration of
electrodes and thus show a gradual decline of
resistance.
A tear down of this spot weld will likely measure
a nugget size of acceptable quality.