The so-called ghosting, also known as "double printing" or "double shadow", that is, the printing product on the entire layout of the local layout or a section of the layout of the double contour, is one of the common faults in the printing process, its production will affect the quality of the product , The result is that the product quality is unqualified and unacceptable to customers. From the phenomenon of ghosting failure, we can see that ghosting features vertical double image and horizontal double image. The reasons for this are unilateral and multi-dimensional. Poor equipment accuracy is also due to improper technical operation, process discomfort and so on. The following are the causes and solutions of the ghosting bugs that have been summarized during the production practice in Putian County, Fujian Province.
First, the cause of the phenomenon of longitudinal ghosting analysis and exclusion methods 1, ink viscosity caused by ghosting too much. When the ink has a large consistency and strong viscosity, a slight slippage occurs during the imprinting process of the printed sheet, which may easily cause the occurrence of a ghosting failure. In particular, when the gripper has insufficient bite force, the longitudinal ghosting is more obvious. In this regard, as long as the proper ink transfer process is turned off, the ink is properly diluted, and the auxiliary agent is used to reduce the viscosity of the ink, which can eliminate the double-image ghosting failure.
2. The printing plate is not taut or ghost caused by the "back pad". At the time of loading, due to a lack of scientific operation knowledge, the fastening screws of the printing plate were gradually tightened gradually, resulting in uneven elasticity of the surface of the printing plate, slight local arching, and back padding of the printing plate. Soft or partial use of multiple pads, pads to make its critical emptiness, are likely to cause local ghosting. In this regard, it is necessary to close the tightening amount of each screw by gradually turning the screw-input amount of each screw into a tight one by adopting a good-fitting-plate-operating-technical-and-padding-process-technique, that is, when the printing plate is strained. Tighten it all at once so that the plate cannot fully and evenly cling to the surface of the roller. On the other hand, the pad used for padding on the back of the plate should be harder and try to avoid local multiple pads or hollowing in order to eliminate ghosting.
3, ghosting caused by excessive printing pressure. When the pressure between the blanket cylinder and the impression cylinder is too high, the displacement of the blanket deformation will inevitably increase accordingly, so that the ink cannot be restored to the original state immediately after the ink transfer during the imprinting process, so that the impression is accepted from the plate cylinder again. At that time, a slight difference in position was generated and ghosting was formed. In this regard, as long as the roller pressure is properly reduced and the expansion and contraction coefficient of the blanket is reduced, this failure can be eliminated.
4. The ghost caused by loose blankets or drums. When the blanket is tightly stretched, the force is not uniform, so that the local position is not closely attached to the surface of the drum, and an emptiness or a drum failure occurs, and when the back of the blanket is adhered to a multilayer pad or a foreign object, it is easy to make Partial layout imprinting ghost. In this regard, the rubber blanket should be released for inspection, and the bad impressions should be re-tightened to eliminate the problem of ghosting.
5, ghosting caused by inappropriate plate or blanket clamping. When the printing plate or the blanket is not clamped, the occurrence of a ghosting failure can easily occur due to the occurrence of a slight loosening during the imprinting process. In this regard, as long as a careful inspection to take appropriate measures, you can eliminate the ghosting shadow failure.
6. The ghost caused by the abnormal work of the drum pressing work. When the parts related to the roller clutch pressure are not adjusted or due to wear, a certain position difference occurs each time the pressure is combined, resulting in ghost images that have different positions. In this regard, as long as the recalibration and adjustment of the clutch-compression mechanism and the repair of the worn-out parts are performed, the drum-disengagement-pressing work will be accurate, coordinated and uniform, and such failures will be eliminated.
7. Ghosting caused by lack of pressure on the paper. When the roller teeth are prone to wear and deformation due to long-term use, the force exerted on the printed sheets during the imprinting is insufficient, resulting in the printed sheets slipping out of the teeth in the imprint during the imprint, and each time the amount of slip is not the same. During the next printing, the ghosting of the fistula area occurred because the fuzzy blots retained on the blanket did not overlap with the retransferred ink. In this regard, it is necessary to check the teething of the drum. If unevenness or insufficiency occurs due to deformation, the moment should be adjusted again. If the surface of the crepe paper is worn, it should be replaced with a new one to ensure that the edge of the paper is not slipped and the ghosting defect can be eliminated.
8, the roller gear or bearing loose wear caused by ghosting. When the printer is used for a long period of time, the maintenance and repair work is seriously carried out, resulting in serious wear of the roller gear or bearing, which inevitably generates vibrations during the imprinting process, and the imprinting of ghosts follows. In this regard, after the worn parts should be repaired, the fault can be eliminated.
9, roller lining discomfort caused by ghosting. When the lining diameters of the plate cylinder and the rubber cylinder are too large, the speed difference and friction occur due to the inconsistent line speed at each imprint, which causes the surface of the blanket to be squeezed and deformed, and the inner spacer can be easily moved. Until the wrinkles, blotting ghosting faults follow. In this regard, the center distance of the drum should be re-measured, and the thickness of the lining should be controlled according to the specifications of the equipment, and the roller line speed should be kept consistent to avoid the occurrence of ghosting and ghosting.
Second, the analysis of the classification and elimination of horizontal ghosting 1. Paper ghosting caused by bad. When the paper surface is uneven and there is a defective condition of the scalloped edge, the paper is subjected to elasticity during the imprinting process, and the paper surface of the arching surface rubs against the surface of the blanket to cause ghosting failure. In this regard, it is appropriate to knock the paper on the surface as appropriate, or to knead and knead the uneven paper surface to promote flattening of the paper surface, in order to achieve the effect of eliminating partial paper surface print ghosts.
2. The ghost caused by poor lining. When the rubber liner lining the pad side too much or less tight. When local hollowing or other conditions exist, partial lateral ghosting failures are also likely to occur. In this regard, the rubber lining should be re-arranged and wrapped. After eliminating the bad conditions, the failure can be eliminated.
3. Difficulties caused by the axial rotation of the drum. When the drum thrust bearing wear, or the thrust bearing screw loose situation occurs, the embossing process will easily make the roller axial sliding, causing the footprint of horizontal ghosting. In this regard, the degree of wear of thrust bearings should be checked and appropriate measures taken to repair them. If the roller thrust bearing is loose, the nut should be tightened and the screw tightly tightened to prevent loosening. This can be eliminated.
4. Ghosting caused by excessive meshing of the backlash. When the gear wears badly, it will inevitably produce shaking phenomenon in the imprinting process, so that the previous and next times of the imprinting can not be accurately superposed, thus there will be transverse ghosting, and even longitudinal ghosting will appear at the same time. In this regard, appropriate repair and adjustment measures should be taken to reduce the backlash of the teeth and reduce the center distance so that the gears can maintain a good meshing state and eliminate ghosting failures.
In short, there are many reasons for the failure of imprinting ghosts, and the situation is also varied. As long as we are good at carefully observing and analyzing the fault phenomenon in our production practice, we can handle such faults quickly and well to ensure the quality of our products. (Futian County, Fujian Province, printing plant Kang Qilai)