Can decreasing force during seam welding cause heating and weld wheel failure?

Seam welding just like spot welding depends upon the proper application of pressure current and time. Let’s assume that the current and time are controlled properly. If the weld force varies during the welding process to lower values, the process is not stable. As the force decreases the contact between the seam weld wheel and the workpiece is not as good as it was with full force. The contact resistance (Rc) between the weld wheel and the workpiece will increase. Rc will become very large and a lot of heat will be generated on the part surface against the seam weld wheel face. This is more heat than the process was designed for with the proper force. Therefore the wheel surface will be over heated and will wear at an increased rate. Mushrooming will increase and if the wheel is being dressed larger amounts of material will be removed. The wheel will be dressed away at a faster rate and need replacement.

The seam weld wheel will fail prematurely due to low or inconsistent force application.

Decreasing Pressure vs Contact Resistance

Decreasing Pressure or Force increases the Contact Resistance

Reference: RWMA – Resistance Welding Manual Section 4

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