FREQUENTLY ASKED QUESTIONS

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.

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.

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 approval to eliminate periodic destructive testing required by MIL-SPEC.  This was achieved by demonstrating the expansion measurements reported by the WeldComputer Adaptive Control correlate with the size and strength of the welds at a reliability level that far exceeds the MIL-SPEC requirements.

While current is not a reliable method of determining weld quality, monitoring the actual current profile over the duration of each weld is important to instantly detect malfunctions with the machine or control.

Control failures such as incorrect duration of applied heat, wrong or inconsistent weld heat delivery are easy to detect with accurate current monitoring.  For operations with multiple machines producing the same components, monitoring current is important to ensure consistent set-ups and schedules from machine to machine.

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.

Increased material pick up on the positive (+) electrode is a physical phenomenon that generally occurs on DC welding machines. Switching to an AC welding process can solve this as well as other problems caused from welding with DC.