Spot welding is one of the most common uses for robots in industry. Most cars have thousands of spot welds joining the chassis and bodywork. People think spot welding is just for high-volume jobs with limited quality requirements. This episode shows how resistance welding can be used for high-quality, precision parts.
Wrapped and welded sand screens are made by resistance welding a wrap wire to the underlying rib wire at over 100 welds per second. But speed is not the big challenge, weld quality and dimensional accuracy are. To achieve good weld quality the electrodes must remain in contact with the part. Any gap will result in sparking and bad welds. If you have seen the video of robots welding cars you might have assumed that sparks were part of the process. They are not. Sparks are never good. On sand screens sparking means you ruined the part. We created low inertia, zero static friction weld head which follows the part and eliminates sparking.
The biggest challenge is holding the gap between wrap wires +/-.001″. Since even the best wire varies by +/-.0007″ most of our tolerance is used by the wire itself. Our closed-loop system compensates for wire width variation in real-time.