function of the electrodes is to conduct the current and to withstand the high
pressures in order to maintain a uniform contact area and to ensure the
continued proper relationship between selected current and pressure. Uniform
contacting areas should therefore be maintained.
weld quality is essential and depends, to a considerable degree, upon uniformity
of the electrode contact surface. This surface tends to be deformed (mushroomed)
with each weld. Primary causes for mushrooming are too soft electrode material,
too high welding pressure, too small electrode contact surface, and most
importantly, too high welding current. These conditions cause excessive heat
build-up and softening of electrode tips. Welding
of today´s coated materials also tends to contaminate the face of the
the electrode deforms, the weld control is called upon to "step" up
the welding current in order to compensate for "mushroomed" weld tips.
Eventually, the production line will have to be shut down in order to replace the
electrodes or to manually go in and hand dress the electrodes. This process will
improve the weld cycle but in either case, the line is stopped and time is lost.
Furthermore the deformed electrodes have caused unnecessary high consumption of
energy and electrodes.
tip dressing, a tip dresser is mounted on the line where it can be accessed by
the welding robot. The robot is programmed to dress the electrodes at regular
time intervals. The dressing can be done after each working cycle, after every
second cycle, and so on. It depends upon how many spot-welds are done in each
cycle. For welding in galvanized sheet, dressing after about 25 spot-welds is
recommended. The dressing takes approximately 1 to 2 seconds, and is perfomed when the work pieces are loaded, unloaded and
transported. Maintaining proper electrode geometry minimizes
production downtime and utility costs and increases weld efficiency.