spot welding(redirected from spot welder)
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spot welding[′spät ‚weld·iŋ]
A resistance-welding process in which coalescence is produced by the flow of electric current through the resistance of metals held together under pressure. Usually the upper electrode moves and applies the clamping force. Pressure must be maintained at all times during the heating cycle to prevent flashing at the electrode faces. Electrodes are water-cooled and are made of copper alloys because pure copper is soft and deforms under pressure. The electric current flows through at least seven resistances connected in series for any one weld (see illustration). After the metals have been fused together, the electrodes usually remain in place sufficiently long to cool the weld. See Resistance welding