General FAQs
QUES. Why should I monitor workpiece
thickness?
ANS. A weld schedule is developed
for a particular material and combination workpiece
thickness. Using the wrong parts for a particular
welding job, extreme mill variation, improper parts
fit-up, or foreign substances on the workpiece can cause
variations in workpiece thickness. Any of these
variations can affect weld quality, so monitoring
workpiece thickness reduces the risk of poor quality
welds due to workpiece problems that could escape
detection by the operation.
QUES. Why should I monitor
displacement?
ANS. Displacement monitoring (nugget
expansion for spot welds, set-down for projection welds)
is a measurement technique that is extremely responsive
to small changes in any of the variables that can affect
the welding process.
Using the expansion monitoring capabilities of the
WeldComputer® Adaptive Control, aerospace companies have
received government endorsement of plans to eliminate
periodic destructive testing required by MIL-SPEC.
QUES. Why should I monitor electrode
force?
ANS. Electrode force - along with
applied heat and time - is one of the key parameters of
a successful weld schedule. Variation in weld force
results in variation in weld quality. It is easy to
predict electrode force by using cylinder pressure
calculations and it is relatively easy to statically
measure electrode force by placing a force gage between
the electrodes. Unfortunately, neither of those methods
is adequate to assure proper weld force during welding.
Plant air pressure drops, cylinder leaks, and inadequate
hold times can result in improper electrode force during
welding. Binding in the welding head, cylinder "stiction",
or excessive head inertia are even more insidious
problems since they are dynamic phenomena that only
occur as welding takes place.
Continuous force monitoring is the only reliable method
of assuring that the specified electrode force is
actually being achieved when it is required: as the weld
is being made.
QUES. Why should I monitor current?
ANS. While current is not a
reliable method of determining weld quality, half-cycle
by half-cycle monitoring of true RMS current can be very
useful in diagnosing machine malfunctions.
For example, control failures such as incorrect number
of cycles of heat, SCR failure, or inconsistent weld
heat delivery are easy to detect by monitoring
half-cycle by half-cycle current values. Benchmarking a
machine's "like-new" performance and monitoring current
over time can provide useful information regarding
periodic maintenance intervals. For operations with many
welding centers producing the same components,
monitoring current can be useful in terms of assuring
consistent set-ups and schedules from machine to
machine.
As an indicator of the quality of any specific weld,
however, current monitoring will only detect the most
disastrous conditions while allowing many bad welds to
escape.
QUES. Why should I monitor
conductance?
ANS. Conductance is the inverse of
resistance. (The higher the resistance, the lower the
conductance and vice versa.) Conductance monitoring is
useful in two general ways.
As welding machines age, conductance gradually
decreases. This means that proportionally more of the
power that was available for welding when the machine
was new (or in good repair) is being dissipated
throughout the welder in the form of heat. Monitoring
the conductance of the secondary circuit of a welding
machine can provide good information regarding periodic
preventive maintenance cycles or requirements for
machine rebuilding.
Monitoring the conductance of the workpiece itself can
provide useful information about its suitability for
welding. Low conductance of the workpiece in comparison
to expectations can be indicative of incorrect material,
corrosion or other surface defect, dirt or other foreign
substances, damaged or dirty electrodes, or improper
parts fit-up. High conductance of the workpiece can be
indicative of incorrect material, flattened electrodes,
and shunting.
Continuous conductance monitoring can provide important
information about the condition of the welding machine
as well as the suitability of the workpiece for welding.
QUES. Can I network my
WeldComputer®equipment?
ANS. Absolutely. Using industry
standard network cards and cabling, we have developed
special network upgrade software that allows the
WeldComputer® Adaptive Control, the WeldView® Monitor
and the WeldView® Plus Monitor to interface seamlessly
to existing communication networks.
