A Comparative Study of Single-Phase AC and Multiphase DC Resistance Spot Welding

[+] Author and Article Information
Wei Li

Department of Mechanical Engineering,  University of Washington, Seattle, WA 98195

Daniel Cerjanec, Gerald A. Grzadzinski

Advanced Mnufacturing Engineering, DaimlerChrysler Corporation, Auburn Hills, MI 48326

J. Manuf. Sci. Eng 127(3), 583-589 (Nov 11, 2004) (7 pages) doi:10.1115/1.1949621 History: Received January 15, 2004; Revised November 11, 2004

This paper presents a comparative study of the AC and MFDC resistance spot welding process. Both experiments and finite element simulation were conducted to compare the weld size and energy consumption. The experiments were performed on two identical spot welding machines, one with a single phase ac and the other with a mid-frequency DC weld control. The machines were instrumented such that both the primary and secondary voltage and current signals could be collected for energy calculation. The finite element simulation model was developed to understand the underlying mechanisms of the difference between the ac and MFDC processes. The effect of the current waveform was investigated by using the actual process measurements as an input to the simulation model. It is shown that the MFDC process generally produces larger welds than the AC process with the same root-mean-square welding current. However, this difference is more prominent when the welding current is relatively low. Overall, the AC welding process consumes more energy to make a same sized weld than the MFDC process. The larger the welding current is used, the less efficient the AC welding process will become. The differences between the two welding processes are caused by the contact resistance behavior and the electrical inductance in the AC welding process.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 5

Primary line currents and phase voltages

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Figure 1

An overview of the experimental setup

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Figure 2

Schematics of (a) the MFDC welder, and (b) the AC welder

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Figure 3

Instrumentation of the secondary side of the transformer

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Figure 4

Typical welding signals (rms welding current is 10 kA). (a) Typical signals of single phase AC welding. (b) Typical signals of MFDC welding.

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Figure 6

An overview of the finite element model

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Figure 7

Dynamic resistances of AC and MFDC welding processes with different welding currents

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Figure 8

Contact resistances for AC and MFDC process simulation

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Figure 9

Nugget growth study for AC and MFDC

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Figure 10

Weld lobes of AC and MFDC spot welding

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Figure 11

Energy consumption at different current settings

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Figure 12

Energy consumption of different weld sizes

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Figure 13

Comparison between the temperature profiles in AC and MFDC spot welding: (a) 9.5 kA MFDC; (b) 9.5 kA AC; (c) 11.5 kA MFDC; (d) 11.5 kA AC

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Figure 14

Simulation results

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Figure 15

Simulated nugget sizes in AC and MFDC processes



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