For design of the AC spot welder control system, on the one hand, we have to consider meeting the control requirements of the AC spot welder, on the other hand, we have to consider the safety of the AC spot welder control system in order to prevent equipment damage or personal injury caused by misoperation or other accidents. At present, the control system of AC spot welder is very mature:
(1) After the whole AC spot welder and the controller are powered on, the system is automatically reset, the control parameters are initialized, the cylinder moves to the initial position, the electrode is in the high position, and each operating condition is detected to determine whether the equipment system is in normal working condition. If the system is abnormal, the control system displays an abnormal warning (abnormal information is displayed through the human-machine interface).
(2) The welding program of the AC spot welder can only be run when both start buttons are pressed with both hands. Only when one of the start buttons is pressed, the welding program can be started. We can avoid pressing the start button incorrectly, which can make the machine run incorrectly, damage the workpiece or equipment, or even cause personal injury.
(3) When the electrode drops, the travel block releases the travel switch SW2, the pressure switch opens and the pressure signal input I0.4 jumps. If the fault reset and emergency stop switches are not pressed at this time, the SCR temperature is normal and the start button is not released, the AC spot welder will be entered for welding. First is the pre-pressure time, then the pressurization time. Preheat time, weld time, hold time and end time. After the AC spot welder welds, the electrode will automatically rise. A second weld can only be made after the start button is released and the start button is pressed again.
(4) After the AC spot welder malfunction, you can press the reset button to bring the machine back to normal operation. At this time, the PLC initializes the control parameters in the control program, such as each status mark, timer, etc., and raises the electrode to a high position. After resetting, press the start button to restart the welding program.
(5) If an abnormality occurs during the welding process of the AC spot welder, the emergency stop switch can be pressed to prevent further welding (or to stop the discharge if it is in progress), and the electrode is lifted and the workpiece is released.
