Model to compensate for shunt of constant current control of robot spot welding

According to the characteristics of the constant current control and the resistance change during the process of spot welding,compensation model to calculate the shunt of the consecutive spot welding was established for three different cases of consecutive spot welding respectively.There is only one nugget in the first case.There are two nuggets in the second case,both nuggets are located on the same side of the spot welding.There are also two nuggets in the third case,but they are located on the both sides of the spot welding.In order to test the reliability of the shunt compensation model for the first case,a simulation model was applied on the fixed type spot welding machine to test the spot shunts under the different dot pitches,materials and thickness.Based on the data tested and calculated,the impact of diversion law was analyzed;the relationship between the shunt of low carbon steel with different thickness,material and the dot pitch as well as the compensation were proposed.Eventually first model validation test on the fixed type spot welding machine was implemented.Results demonstrate a substantial improvement of weld quality and reduction of process variability with the proposed compensation model.