The so-called automation equipment fault diagnosis is divided into fault diagnosis during debugging and fault diagnosis during operation. The only difference between the two is that commissioning is the first run of the device, and failures can occur at any point before it works properly. The fault diagnosis during operation means that the equipment has been working normally, but due to some reasons, it suddenly does not work or does not work according to the normal motion sequence.

　　Fault diagnosis in two different states is different in thinking. If there is a problem during debugging, there may be a fault in the controller or the program. However, if a problem suddenly occurs during operation, do not focus on the controller and the program, because the program will not change itself without manual modification. Today's controllers are of very good quality and rarely fail for no apparent reason. Unless there is serious electromagnetic interference.

　　Some people say that fault diagnosis depends on experience, and they think that older engineers are more experienced and better able to handle fault diagnosis. But does age represent qualifications? Does age represent experience? What really determines the level is thinking! To deal with different problems, it depends on whether your thinking is correct and whether your working method is correct!

　　When a piece of equipment suddenly has a problem and does not work, or the work sequence is out of order. Many people will think whether the program is wrong? PLC is broken? Many engineers often think so. That would be dead wrong.

　　If the program is wrong, how could your equipment work before? No matter what brand of PLC it is, it is impossible to suddenly break down when it is working normally. The probability of this is lower than winning the 80 million jackpot. So how should the problem be considered?

　　First of all, we have made it clear that the equipment is divided into three parts, then we will carry out fault diagnosis step by step in the following fixed order. As long as you follow the following order, no matter what kind of equipment, you will find the problem easily!

　　1. Check all power sources, air sources and hydraulic sources

　　Power supply, including the power supply of each piece of equipment and the power supply of the workshop, that is, all power supplies, air sources (including those required by pneumatic devices), hydraulic sources (including the working conditions of hydraulic pumps required by hydraulic devices) that can be involved in the equipment ).

　　In 50% of the fault diagnosis problems, the faults are the problems of power supply, air supply and hydraulic supply. For example, there is a problem with the power supply, including the failure of the power supply of the entire workshop, such as low power supply, burnt insurance, poor contact of the power plug, etc.;

　　The air pump or hydraulic pump is not turned on, the pneumatic three-piece or two-piece is not turned on, the relief valve or some pressure valves in the hydraulic system are not turned on, etc. These are the most basic questions and are usually the most common ones.

　　2. Check whether the position of the sensor is offset

　　Due to the negligence of the equipment maintenance personnel, there may be errors in the position of some sensors, such as not in place, sensor failure, sensitivity failure, etc. Always check the sensing position and sensitivity of the sensor, and adjust it in time if there is a deviation. If the sensor is broken, replace it immediately.

　　In many cases, if the power supply, air source and hydraulic source supply are guaranteed to be correct, the more problem is the failure of the sensor. Especially for magnetic induction sensors, due to long-term use, it is likely that the internal grounds will stick to each other and cannot be separated, and a normally closed signal will appear. This is also a common problem of this type of sensor and can only be replaced.

　　In addition, due to the vibration of the equipment, most of the sensors will loosen after long-term use. Therefore, during daily maintenance, it is necessary to check whether the position of the sensor is correct and whether it is firmly fixed.

　　3. Check the relay, flow control valve and pressure control valve

　　Relays are the same as magnetic induction sensors. If they are used for a long time, they will also stick to the ground, so that the normality of the electrical circuit cannot be guaranteed, and they need to be replaced. In a pneumatic or hydraulic system, the opening of the throttle valve and the pressure adjustment spring of the pressure valve will also loosen or slide with the vibration of the equipment.

　　These devices, like sensors, are parts that require routine maintenance in the equipment. Therefore, in daily work, these devices must be carefully checked.

　　4. Check electrical, pneumatic and hydraulic circuit connections

　　If no problem is found in the above three steps, then check all circuits. Check whether the wires in the circuit are broken, especially whether the wires in the wire slot are cut by the wire slot due to pulling. Check the trachea for damaging creases. Check if the hydraulic oil line is blocked.

　　When checking the circuit at this step, use the necessary multimeter, set it to the buzzer position, and check the circuit connection. If the trachea is severely creased, replace it immediately. The hydraulic oil pipe also needs to be replaced.

　　After ensuring that the above steps are correct, the fault may appear in the controller, but it can never be a program problem! First of all, don’t be sure that the controller is damaged. As long as there is no serious short circuit, the controller has short circuit protection inside. A general short circuit will not burn the controller.

　　First, check whether there is any high-frequency interference device near the controller. If so, remove it immediately. If it is outdoors, the high-intensity lightning may also cause the controller to fail to work normally for a moment. At this time, remove all possible interfering devices first, and then restart the controller.

　　Secondly, if restarting does not work, check whether the controller wiring is loose or in poor contact.

　　Finally, if the wiring is correct. Determine whether there is a problem with the memory card of the PLC. Replace a new card, download the program, and check whether the previous memory card is faulty.

　　If all the above measures are ineffective, then you are lucky, you have encountered a failure with a probability of no more than 0.01% in the world, congratulations! Please contact the factory engineer or replace it with a new one.