Dr. Livingstone, I Presume WELDWISE 2400 - Manual (Page 23)

0429-INS-400 Rev. C 2-5
air over oil cylinders. If the electrode force drops too low, resistance can increase between the
electrodes and the workpiece, resulting in expulsion. If the electrode force becomes too great, the
resistance is lowered, resulting in poorly formed nuggets or even brittle welds, particularly with coated
metals. Excessive force also reduces electrode life, causing tips to mushroom more quickly.
Electrode displacement, measured in inches or millimeters, indicates the relative movement of the
electrodes during the welding process. The displacement measurement corresponds with the nugget
formation at the weld site: as the materials being welded become molten, the metal expands, pushing
up against the electrodes. Force is maintained as the electrodes push back, applying pressure to the
weld. Follow-up force is critical in containing nugget expansion and in eliminating weld expulsion.
How Monitors Work
Typically, a weld monitor receives input from the welder through a variety of sensors that can be
configured for specific applications. These sensors measure the characteristics of the weld process and
transmit this data to the weld monitor. Toroids are used for measuring current, and pressure sensors or
load cells are used for measuring force. Relative movement of the electrodes during welding is
measured using displacement sensors, while voltage leads measure voltage at the weld head. Data is
collected from all or a combination of these sensors and displayed by the halfcycle, cycle or average
for the entire weld, depending on the type of monitor used. The more weld parameters monitored, the
harder it is to unknowingly make a bad weld. Using a Dynamic monitor, factors that may adversely
affect the quality of a weld can be easily tracked and identified, and the exact moment when a problem
occurs can be isolated, down to the halfcycle.
A weld monitor will not control the weld process, nor will it inform the user what the process
parameters are supposed to be. It will confirm if welds are made within the limits set by the user, and a
monitor can be used to simplify methods of refining process parameters. It's important to understand
that the user first needs to define the weld lobe and proper weld schedule. Once a weld lobe and
schedule are established (according to internal standards, or through trial-and-error), monitoring can
begin.
More Benefits
Below are additional benefits of weld monitoring:
• Optimize weld schedules for individual parts and conditions.
• Ensure a 100% inspection level— every single part being produced can be monitored in
seconds and the resulting weld data compared to known good values.
• Detect weld setup problems and maintenance issues before they cause bad welds.
• Provide traceability of welded components— the recorded hard copy or electronically stored
weld history helps ensure regulatory compliance in specialized industries.
• Minimize production downtime— if a welder isn't working properly, the problem can quickly
be tracked down and repaired faster. Less downtime means more money!