When a resistance welding machine is initiated but then does not start the cycle there is usually an I/O signal missing to the controller/timer. There are several Inputs that could cause this to happen. The problem is even more complex to troubleshoot when a PLC or other controls are interfaced with the RW unit or controller. We'll go over just the RW timer/controller.
First, if nothing happens then the signal probably never made it to the timer in the first place. The problem could be the foot pedal or palm switches that is; the latch for the welding (foot pedal switch, palm buttons etc.) is bad. Also there could be prox. switches in series that are not letting the signal go through. Test the components individually one at a time. Make sure you are not even close to any pinch points and that the RW machine is in "no-weld"!
If the lights on the timer flash as normal then it could be the air valve. If the lights are not normal then it is the timer itself or additional I/O that are tied into the timer.
Sometimes timers/controllers are set up for checking things before the weld is made. This is a reliability issue or possibly more PLC I/O. Often seperate devices will "pull out" an Input signal to keep the machine from welding. There might also be a lack of water flow, not enough air pressure, or other inputs to let the machine start. This is an I/O problem and depends upon how it is interfaced with the robot, machine or controller/timer.
There are many different manufacturers' controller/timers for resistance welding. There are also many different models from these companies and many additional ways to program and set up different I/O functions. Your controller/timer manual should be available if the machine is less than 10 years old. To go to our controller links page click here.
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