monitoring can help you spot setup or electrical problems.
Often, bad welds are produced because an operator improperly sets the
welding control. Sometimes, unauthorized adjustments have been made.
With wear, electrodes may have "mushroomed" until current density is
too low, requiring tip-dressing or replacement. Electrical connections
may have loosened, or cables may have been frayed.
monitor can also help you discover mechanical problems. The airline
regulator may fail to deliver the required pressure. Weld current may
start to flow before adequate electrode force is reached. Tooling may
have worn or fixtures may be improperly assembled. A fastener, such
as a weld nut, may have been positioned upside-down. Hold time may not
be long enough to ensure proper and consistent setdown.
process optimization standpoint, you may find that welding time can
be shortened. The need for extra safety welds can be reduced because
the primary welds you have made are known to be of consistently high
quality. Of course, you may find that you need to extend welding time
to improve quality.
these cases, measuring as much that goes on during the weld cycle as
possible - current, voltage, cycles, resistance, force, and displacement
- will help you develop the best weld schedule for your application.
This measurement will help ensure higher weld quality with less need
for destructive testing. Your ability to describe in numeric terms what
a good weld is and to recall its signature for comparison with subsequent
welds will help prevent rejects. In short, the more you measure, the
more you know.
concerns are another driving factor behind the implementation of weld
monitoring. Inadequate weld quality can involve both loss of productivity
and safety issues. The definition of some automotive welds as MVSS (Motor
Vehicle Safety Standard) means they must be monitored and known to be
good. The failure of an MVSS weld may result in personal injury.
requires that you know what your process should be and prove it with
documentation. In many instances, the ability to evaluate welds according
to a statistical process control (SPC) sampling plan is adequate. In
other situations, the characteristics of each weld must be recorded.
The existence of printed documentation of weld quality is a requirement
for proof of process.
that monitoring itself is not a solution to weld problems. You need
to make monitoring work for you, and learn what monitoring trends are
if welds are suddenly rejected, you might find that the welding control
settings have been changed. By noting the monitor's time and date stamp
on the weld record (if the monitor provides this), you can determine
when the change was made. In another instance, you may find that current
and voltage are decreasing over a large number of welds. This might
point to problems with the secondary connections or cables. Next