Examples and solutions of electrical faults of the

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Examples and solutions of electrical faults of rotary printing machine

our factory has a "nordi" brand six color rotary commercial form printing machine, which is imported from Spain. Among the domestic agents, there are few agents for the printing machine of this brand name, so when the machine has a more complex failure, it can only be solved by transferring to the Spanish manufacturer in Hong Kong, which is very inconvenient. In recent years, I have encountered many failures in the process of managing and participating in the maintenance of the machine, which is common in the rotary printing press. This paper introduces some examples of electrical faults for reference

I. tension system failure

in production, workers measure the tension of products by placing the products on a three meter measuring ruler, and then adjust the tension. When the tension system breaks down, the tension of a roll of paper measured during printing is very unstable, and no matter how to adjust the tension data of the machine, it cannot reach the ideal; At the same time, the tension rod will float up and down during operation, that is, when the diameter of the paper roll is still 20 ~ 30cm, the tension system will disappear after the adjustment is stable, whether in cars, medical treatment or ordinary life scenes. Through analysis, we found that when the diameter of the paper roll is large, although the tension is unstable, there is still room for adjustment, indicating that the control circuit of the tension system has not failed. The balance force of the tension bar is adjusted by the magnetic drum. The tension magnetic hub of this model is permanent magnetic rather than electromagnetic. Because the machine has been running for many years, the loss is large, resulting in uneven magnetic force, which is easy to cause tension instability. At this time, if you don't want to replace the magnetic hub again, you can solve it in this way: wipe out the worn magnetic particles, clean them with gasoline, and carefully grind the contact surface, which can temporarily solve the fault of this kind of tension system. To make the magnetic hub durable, it should be maintained regularly at ordinary times. Remove the magnetic hub every six months, wipe away the worn magnetic particles around, and carefully inspect the surface

II. Common faults of main motor

printing machines usually use DC motor as the main drive motor. Our "Nordy" brand printing machine uses this type of motor. Its most common fault is the spark between the brush and the commutator, which burns the surface of the commutator. When the motor runs abnormally, it shows that the speed slows down, and it runs tremblingly at low speed. At high speed, it runs unsteadily, and there is a rattle, which seems to be an abnormal sound from the rotating shaft, making people think that the bearing of the rotating shaft is broken. So when you hear this abnormal sound, don't easily judge that it is the fault of the bearing, so as to avoid doing a lot of useless work. It is suggested to check the brush and commutator of the main motor first. Normally, the spark between the brush and the commutator is light blue, weak and fine, the contact surface of the brush is smooth and bright, and a layer of reddish brown oxide film is formed on the surface of the commutator; In case of fault, the spark is yellow red and bright, which makes the contact surface of the brush uneven, and the surface of the commutator blackened and burned. Of course, strong sparks will also appear when the brush deviates from the geometric neutral line or the armature winding is open or short circuited internally; In addition, too much or too little brush pressure or poor grinding, and too few contact surfaces will also produce fault sparks. In addition, the above abnormal sound will also occur when the main motor power supply is out of phase, but it will generally be accompanied by a weak buzzing sound

III. tachometer generator fault

when the machine is running, if it seems that there is a strange sound from the rotating shaft, and the speed instability is obviously observed at low speed, the speed number indicated in the speed display on the operating surface jumps up and down within a certain range, but Koizumi 1, who can use the knob to draw and create art, has always regarded himself as a newcomer for speed regulation. At this time, first check the tachometer generator and check whether its belt is loose. Because the speed measuring generator is driven by the main rotating shaft, the voltage signal output by the speed measuring generator is fed back to the main board, and the closed-loop system with this negative feedback is used to adjust and control the main engine. The looseness of the belt will directly affect the voltage stability fed back to the main board, so that the speed of the host fluctuates, resulting in abnormal sound when the rotating shaft is fast and slow. If there is no problem with the belt, nine times out of ten the tachogenerator itself is faulty. As long as a group of winding wires are disconnected from the rotor of the tachogenerator, the above fault will also occur. It is troublesome to judge whether the speed measuring motor has a fault, unless the motor is burnt out. If only a group of winding wires are broken, the output voltage when it rotates is basically stable and linear when measured with a multimeter. In this case, the speed measuring motor can only be disassembled and each group of winding wires can be measured patiently. There is a big difference between imported speed measuring motors and domestic ones. Most of the imported motors are quadrupole motors, which are very small in size and winding. They are very easy to break through the expanded Wertheim factory. When maintaining, you must go to a professional maintenance Office for maintenance

IV. abnormal fault of automatic shutdown for no reason

this kind of fault is relatively rare, but I encountered it once in the management equipment. The fault is like this. The machine will stop automatically for no reason during operation. What the operator needs to point out is that the "10" shutdown symbol code and the "00" normal startup symbol code appear alternately on the display on the operation panel, so that the operator cannot start the machine normally. Sometimes it stops automatically after 3 ~ 5 minutes of operation, and sometimes it can run continuously for several hours without any failure. We first checked various switches, especially the shutdown switch, and found no abnormality; Check the light on condition of the driver. As the information provided by the manufacturer, the driver can work normally without any suspicious fault; No disconnection or loose interface was found. In this case, we can't solve it by racking our brains. In the end, we can only think that there is a problem with the switch again. In particular, the commonly used shutdown switches, although we did not find any abnormality during inspection, are the most commonly used after many years of use, which may appear to be disconnected. Later, all the commonly used shutdown switches were replaced, and indeed, the unexplained shutdown phenomenon disappeared

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