Trouble shooting for offset printing (4)

Trouble shooting for offset printing (4)

Section 3 Judgment of abnormal sound of machine parts

As a skilled technician in the operation of offset presses, it is necessary to develop ear hearing skills in daily production. Because there are many parts of the offset press, and the sounds of various parts during operation have a fixed tone and beat, the operator has to identify which part of the sound has changed, so as to find the problem. Hearing skills are particularly important to ensure the safe operation of the equipment, because most of the components of modern offset printing machines are enclosed in the casing, invisible to the eyes, and cannot be touched by the hands. The only thing that can be felt by people is that they are emitted during operation. Sound, this requires that in normal work, pay attention to the sound that the machine parts make when they are normal, and listen to and remember clearly. The average operator's minimum requirement is to "check the disease by smelling sound." If it stays at this stage, it is obviously not enough. Operators with real skills should strive to "know the disease by smelling sound." This "knowing the sound and knowing the disease" is a great skill, and even the provisions that should be known should not be included. The following are some rough experiences of the author in practice.

1. The abnormal sound made by the parts outside the hood when they are not working properly

â‘ J2108, J2203 and J2201 offset presses sometimes make a "squeak-slap" sound. The "squeak" sound is sharper, and the "slap" sound is louder but it seems not neat. This is the sound that the tip of the swinging tooth touches the empty edge of the impression cylinder. Or the sound of the paper collecting teeth and the tip of the teeth touching the empty edge of the impression cylinder. Because the tip of the tooth is sharp, when the anti-point is scraped, it slides against the neutral edge of the roller, and there must be a sharp "squeak" sound. The "slap" sound when the tooth is closed is not neat. Close your teeth, and slowly close your teeth while scratching the gap, so the "slap" sound will not be neat.

The swinging tooth tip touches the blank edge of the impression cylinder, and the position of the large cam can be adjusted or the diameter of the roller is increased; the paper collection tip touches the blank edge of the impression cylinder, and the running time of the paper row can be adjusted as a whole .

â‘¡The sound of "Boom, Boom" is made when the drum is running after being pressed, and the pressure used by the machine is too high. Sometimes the sound of "clap, crap, crap" is that the printing plate is not strained or broken. The former needs to reduce the pressure between the rollers, the latter needs to be tightened or replaced with a new printing plate.

â‘¢ When the paper stack is full of paper and printing is started, the paper feeder makes a sharp "squeak-squeak" sound like every piece of paper. This is because a small paper stopper (crushing) hits the paper transfer roller. Loosen the screw in the middle, and let the fixed foot sink a little.

â‘£The paper stack rises up and the suction iron keeps ringing continuously, but the paper stack does not rise. This is because the pin of the continuous iron core is broken or is about to slide out. It should be stopped immediately and connected Get it right.

⑤ During the printing process, the sound of "burst-burst-burst" is emitted every time a piece of paper is printed, which shows that the pressure of a certain water and ink roller on the printing plate is too high. Because the ink roller and water roller are made of rubber, the sound is relatively dull. Which one do you want to check? Did the adjusting screw move? Then adjust it.

â‘¥ The sound of "snap, slap, slap" from the bottom of the machine's paper collection part, this is because the paper collection chain is too long, the swaying force of the tooth row when turning is generated on the guide rail, and the paper collection chain on both sides should be properly tightened .

⑦The paper-receiving stacking platen rises too high and hits the paper-collecting suction rod. The suction wheel will make a "squeak-squeak" sound. It can move the suction eye down and the sound should be Will disappear.

The above are frequently heard abnormal sounds and troubleshooting methods.

Second, the sound made by the internal parts of the hood

â‘  The internal parts of the hood are most easily damaged by ball bearings, especially on the transmission side, such as the rollers on the large swinging cam and the bridge gears in the lower transmission part, which are equipped with ball bearings. After the ball bearing on the gear is damaged, the gear will make a "boom" sound during operation. This is mainly caused by the gear meshing abnormally and excessive friction on the tooth side. It is usually accompanied by a "boom" sound. When these sounds are found, the cover should be opened for further inspection. Sometimes after opening the cover, it is difficult to determine which part at a time. At this time, you can use the "auscultation method" to determine it. The specific method is: use a long-handled screwdriver, the knife edge contacts the machine, the knife handle is placed next to the ear to listen, which machine There is a problem with the piece, and the sound that comes into the ear through the handle will be different. With this "auscultation method", the proportion of confirmed "symptoms" can be said to be 100%, which can reduce many unnecessary troubles of repeated disassembly and assembly. This "auscultation method" can also be applied to the abnormal sound failure of other machine parts such as motors.

â‘¡If the machine stops suddenly, it can be confirmed that the hard screws and other parts have fallen off, and the "smooth car" failure caused by the failure of the safety insurance device at the paper feeding position. If the machine is stopped gradually, it is generally caused by the lack of oil in the main parts such as multiple sheets of paper entering the rollers or roller sleeves. When finding no obstacles in multiple ways, you can remove the boot and touch the bushing and other parts one by one. If you find a hot or hot part, you can confirm that it is caused by the lack of oil and welding. Grinding and welding of the bushing caused by debris entering the bushing are generally non-existent on modern offset presses except for manual refueling, because the automatic lubrication mechanism has multiple layers of filters and filters. However, some oil pipelines are broken, and oil-free shutdown failures caused by blockages also occur from time to time.

When the machine suddenly stops malfunctioning, the operator should immediately turn off the main motor power to prevent unnecessary losses such as burnout of the motor. If it is found that the blanket slips out of a long mouth without stopping, it means that parts and other objects have been rolled in between the rollers and slipped from the roller gap into the machine pit. It should be stopped immediately to check the cause.

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