Spot Welding

Questions and Answers

Spot welding electrodes have a large influence on the resistance welding process. Their alloy and face size contribute to the development of the proper weld nugget. All of this assumes that the electrodes have been installed properly. This means proper water cooling and water tube location and good alignment. Alignment means that the face of the electrode is square and parallel to the part being welded. In addition the upper and lower electrodes faces should line up vertically with each other. The goal is to apply all forces on the same central axis. This prevents the electrodes from imparting and twist or distortion into the part during the welding operation.

Edge distance is a very important design criteria in resistance welding. Any weld on an edge can expel metal and or result in a partial weld nugget. This type of weld is considered deficient in quality programs. Edge welds should be avoided in all design and set up situations.

Part fit up is very important in determining the quality of resistance welds. All weld schedules call out a force value with the purpose of holding the part together, containing the weld nugget and performing a little forging as the weld cools. If the part does not fit up properly then part of this force is used to force or form the part into place and is not available to contain and forge the weld nugget.

Resistance welding over a lip, in a corner, or in a box might be a perfect application for a double bend electrode.

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