So you have purchased the best possible welding system. Does this ensure that your process will always be under control? Not exactly. Here are just a few things that can affect weld quality:

Material Changes: If purchasing manufacturing materials from one supplier, or many suppliers, material alloy, surface conditions, oxidation and mechanical configuration can change from batch to batch. The weld control can accommodate some of the inconsistencies, but not all of them.

Equipment Changes: Weld heads can create inconsistency for a number of reasons. Force can change due to air leaks and miss-adjustments. If the shop air goes too low, weld head force diminishes. Heat can change due to different electrode geometries or electrode alloys. If the secondary breaks down, weld current diminishes. Weld controls are not perfect either. After years of service, output may change if the system is not calibrated regularly. Damage to the weld control, weld head or weld transformer can also cause decreases or increases in weld current or weld force.

Operator Changes: Sometimes, operators make changes that can affect a process in a negative manner.

Weld checkers and weld monitors can track various measurable parameters, which include the following:

Secondary Current

Secondary Voltage, (voltage measured at welding electrodes).

Secondary Resistance

Secondary Power

Secondary Force

Secondary Displacement

Welding Time

Conduction Angle, (for AC welders)

Weld controls can keep particular parameters under control, but there are some that the welder is incapable of recognizing. External weld monitors and weld checkers are considered to be the best tools for maintaining process consistency.

Weld monitors are precise, calibrated measuring tools, which measure some or all of the parameters listed above. Upper and lower limits can be set around parameters so alarms can be generated if the process goes out of control. Most weld monitors have I/O that can communicate with a PLC to ensure consistency in an automated process. Many weld monitors also have data communications so monitored values can be collected by a PC.

Besides measuring secondary current and voltage, some weld monitors can measure displacement, (part collapse during a weld). In some applications, part collapse is the determining factor in weld strength. In others, adequate part setdown is the most important factor. For either situation, weld checkers with this capability can shut off the welder’s current flow and measure the final displacement.

Some weld monitors have force measurement capabilities. Some measure force at the welding electrodes. Other weld monitors can read load cells that are buried inside of weld heads.

To effectively choose from the many weld monitors and weld checkers, determine which variables have the greatest affect on weld quality, then apply the monitor that will assure the process stays in control.