Offset paper delivery device common faults and solutions
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The printing suitability of different sheetfed offset presses is quite different. Different thin and thick papers have different problems in the delivery device when printing different graphic information. In this paper, the author focuses on analyzing the common faults and solutions of the delivery device. Peer reference.
The print on the surface of the take-up reel is dirty
1. Anti-smear treatment method
(1) Adjusting the position of the star wheel
The domestic offset printing machine generally adopts the skeleton type delivery roller, and has a simple structure. By adjusting the position of the star wheel, most of the printed products can be prevented from being dirty, and the manufacturing cost is relatively low. This method is generally suitable for black and white or relatively simple color prints.
(2) Anti-mite cloth / anti-smudge paper (glass ball sandpaper)
A tamper-proof cloth can be installed on the surface of the flat take-up reel, such as Heidelberg's super blue cloth. The surface structure can reduce the contact area with the paper and cushion the shock absorption to achieve the purpose of preventing smashing; On some Japanese offset presses, you can manually put anti-smudge paper (glass ball sandpaper), relying on the sharp points on the surface of the glass ball sandpaper to hold up the surface of the print, so as to prevent smudging, but after using the glass ball sandpaper for a long time, The ink gradually fills the gap between the sphere and the surface of the sphere, making it lose its anti-smashing effect. Therefore, depending on the application, it is recommended to scrub it once a day to extend the life. It should be noted that whether it is super blue cloth or anti-smudge paper, after a certain period of time, the anti-smudge effect will be reduced and it needs to be replaced regularly.
(3) Anti-sludge air cushion roller
The anti-smashing air cushion cylinder belongs to the patented technology of Roland offset printing machine, which is easy to operate and can last for a long time. However, due to the high manufacturing cost, only high-end models have this feature, or you need to purchase this feature when purchasing equipment.
2. Pickup roller surface cleaning method
Regardless of the type of anti-smashing device, it is necessary to regularly clean and scrub the surface to ensure that the surface is clean and there are no ink bumps. It is recommended that the operator scrub the surface of the delivery roller or use a wind gun to wash the tamper every day after work. Dirty cloth.
Paper reducer (brake roller) does not have enough air intake
1. The overall deceleration effect is poor
(1) Fault phenomenon
When the paper reaches the stack, it curls forward and collides with the front paper stopper. The curling and tearing of the crevice occurs. Adjust the suction volume of the delivery reducer and adjust the angle of the open cam to change the arrival of the paper. After morning and evening time, the effect is still not good, and it is basically determined that the reducer has insufficient air intake.
(2) Solution
First check whether the external suction filter of the reducer air pump accumulates a large amount of dust and debris, and then check whether there is a large amount of dust on the built-in filter of the reducer, the air filter device sucked by the air pump and the dust sprayed during operation of the reducer. The filter device is inspected and cleaned to determine that the speed reducer is normal. Under this premise, increase the intake of the reducer and eliminate the fault.
2. The local deceleration effect is poor
(1) Fault phenomenon
The visual effect of poor local deceleration is that the paper is skewed in one direction. In severe cases, the skewed paper hits the safety device and causes parking. The poor local deceleration effect also reduces the speed of the printing equipment. This is usually caused by a deceleration wheel on both sides of the paper reducer. Gas or blockage is caused by no inhalation.
(2) Solution
In the stop mode, firstly through the jog control, the paper reducer is exposed to make a certain operation space and press the emergency stop of the delivery device control panel to avoid a safety accident; manually open the delivery air pump switch, take Take a piece of cut paper and test it on the surface of each reducer. Under normal circumstances, the paper is obviously sucked, but if there is no inhalation, it is necessary to determine whether the suction port is blocked, the suction port seal is aging, or the whole Block the pipe (disassemble the suction pipe below the reducer, test the suction pipe for suction) and clean it.
Flat paper fan and flat paper duct are uneven in air volume
The flat paper fan, like the flat paper duct, works with the paper reducer to drop the paper that has been decelerated quickly and smoothly onto the surface of the stack for paper jamming. Under normal circumstances, small-format offset printing machines take into account the space problem of the equipment, and most of them use air ducting paper. The large-and-medium offset printing machine uses fan air ducts at the same time to enhance the flat paper effect. The operator needs to be independent of each air duct. The air volume and the overall air volume are adjusted (usually the air volume of the air duct needs to be adjusted uniformly, up to 80% of the total; the fan air volume is usually controlled at 50% to 80%); the 100% overloaded air condition will cause the wind The pump is in a high pressure and high temperature state for a long time, which seriously affects the service life. It is recommended not to open to the maximum state.
Under normal circumstances, the fan air volume adjustment is consistent, and no independent adjustment; if the image information (ink amount) is unevenly distributed (such as one side of the solid printing, one side of the text printing), the paper is skewed, you can rebalance the fan and The amount of air blown by the air duct reduces the skewed state of the paper, so that the delivery is smooth again. It is also possible to pad the wedge on the side of the first paper, and to make it fall quickly by increasing the height, so that the paper passes smoothly. In addition, the dust on the surface of the fan and the blowing port of the flat paper duct should be cleaned regularly to prevent clogging.
Paper speed reducer (brake roller) is not suitable for rotation speed
1. The speed is too slow
(1) Fault phenomenon
Regardless of the thickness of the paper, when the speed reducer is inhaled normally and the speed is too slow, the moving paper will accumulate on the surface of the reducer, eventually causing the reducer to lose its function, and paper picking problems such as paper jams and roll papers may occur.
(2) Solution
In the actual production, through the printing paper, the paper-receiving state is observed at different speeds, and the speed of the speed reducer is manually adjusted to achieve a smooth delivery. When printing thick paper, the operator must not only adjust the current speed of the reducer, but also adjust the running time of the open cam to avoid the occurrence of dirty scratches.
2. The speed is too fast
(1) Fault phenomenon
When printing on one side, the speed of the reducer is too fast, and the fault phenomenon is not obvious. When the double-sided printing is performed, since the speed of the reducer is faster than the speed of the moving paper, the surface information of the paper on the printed side is excessively rubbed, thereby Scratches occur; when thinner paper is printed, excessive curling and cracking of the paper may occur.
(2) Solution
When printing on both sides, it is necessary to continuously check the quality of the reverse image, adjust the speed of the reducer in time, observe and judge the quality of the delivery, adjust it in time, and master the operation skills and rules. Pay attention to the air blower of the air cushion fan, and use the force formed by the fan to form an air cushion between the reducer and the paper to avoid smudging.
In the process of troubleshooting, the operator must be good at observing and analyzing the fault phenomenon, correctly and reasonably adjust the working state of each delivery device, regularly do the maintenance and maintenance work of each device, adhere to the "complex problem, simple start" The logic of thought uses the elimination method to find out the cause, eliminate the fault, and improve the effective production time.