Resistance Welding & Consulting FAQs

Frequently asked questions about WeldComputer Corporation’s products, services and technologies.

A resistance 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.

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.

Electrode force – along with applied heat and time – is one of the key parameters of a successful resistance 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.

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.

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 resistance 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 resistance welding.

Absolutely. Using industry standard network cards and cabling, we have developed special network upgrade software that allows the WeldComputer® controls and WeldView® monitors to interface seamlessly to existing communication networks.

Yes, but that’s not all. It also has a frequency compensation system that automatically provides heat compensation for even widely varying line frequency. While this feature is not usually necessary in the United States, it’s virtually required for proper heat regulation in many other parts of the world. And, unlike most conventional resistance welding controls, the WeldComputer control prohibits welding when it can’t deliver the specified heat and notifies the operator of the reason.

In addition to providing all of the conventional control functions, the WeldComputer® Adaptive Control can monitor all the key welding parameters (current, force, workpiece thickness, thermal nugget expansion/ displacement, conductance and energy) on a cycle-by-cycle basis, compare the results to expected values, and compensate for variation as the weld is being made to assure the quality of each and every weld.

Of course. Even though the WeldComputer® Adaptive Control was designed for high reliability in harsh production applications, it is a valuable asset for any welding laboratory. The WeldComputer® Adaptive Control can’t be beat when it comes to developing robust weld schedules and experimenting with different resistance welding parameters. Just because the WeldComputer® Adaptive Control is easy to use should not obscure the fact that it is the best analytical instrument available for welding laboratories.

The control portion of the WeldComputer® Adaptive Control is no more difficult to install than most conventional resistance welding controls. The sensors used for monitoring and adaptive control take some extra effort but are well worth it because of the benefits gained. We have installation experts to assist “do-it-yourselfers” or we can supply turnkey solutions.

Most resistance welding controls don’t have any way to check their work (and none can check their work as well as the WeldComputer® Adaptive Control). Some manufacturers want to provide a level of quality assurance to their resistance welding operations so they utilize monitors to check the work of their welding machines. Unlike other monitors, the WeldView® Monitor is designed for production process control and, unlike other monitors, the WeldView® Monitor checks more than just electrical parameters.

The WeldView® Monitor can be configured to check from one to eight welding heads (i.e., sets of electrodes) simultaneously for all key welding parameters.

The WeldView® Monitor can be configured to monitor current, voltage, conductance, energy, workpiece thickness, displacement, and electrode force for every half cycle of every weld (or, in the case of inverters and cap discharge welders, as frequently as every 10usec!).  Actual values are compared to upper and lower limits of acceptability and the system provides a fault signal output if any parameter is out of limits.