Exclusion method for several faults in imprinting
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Blotting ghosting is one of the common faults in the printing process. Its lightness affects the quality of the product, and the quality of the batch is unqualified, which is unacceptable to customers. Therefore, only by analyzing the root cause of the fault and accurately and quickly eliminating this fault can we ensure the smooth progress of production.
The so-called ghost image, also known as "double print" or "double shadow", that is, the entire layout or partial layout or a certain layout on the printed product has a double imprint outline. It can be seen from the phenomenon of ghosting that the characteristics of ghosting are vertical double shadow and horizontal double shadow. The reasons are both unilateral and coexisting in many aspects. There are poor precision of equipment, and there are also technical operations, process discomfort, and so on.
I. Analysis and elimination of the situation of vertical ghosting of the imprint
1. The ghost caused by too much ink viscosity
When the ink consistency is large and the viscosity is strong, the printed sheet produces a slight slip phenomenon during the imprinting process, which easily causes the occurrence of ghosting failure, especially in the case of insufficient gripping force of the gripper, and the longitudinal ghosting is more obvious. In this regard, as long as the ink is properly closed, the ink is appropriately diluted, and an additive is added to lower the viscosity of the ink, thereby eliminating the ghosting failure.
2. The plate does not have a taut or ghost of the "bottom pad"
When installing the plate, due to the lack of scientific operation knowledge, the plate fastening screws are not evenly tightened in order, so that the surface of the plate drum is tight, the part has a slight bow shape, and the pad on the back of the plate is too soft. Or partial use of multiple pads or less pads to make the critical emptiness, it is easy to cause local ghosting. In this regard, it should be closed by the good installation technology and the lithographic process technology, that is, when the printing plate is tightened, the screwing amount of each screw should be gradually tightened evenly, and it is forbidden to put a certain screw first. The child is tightened. The plate cannot be completely and evenly attached to the surface of the drum. On the other hand, the padding used for padding on the back side of the plate should be harder and try to avoid partial padding or hollowing out to achieve the effect of eliminating ghosting failure.
3. The ghosting caused by excessive printing pressure.
When the pressure between the blanket cylinder and the impression cylinder is too large, the amount of displacement and displacement of the blanket will increase accordingly, so that the ink cannot be restored to its original shape immediately after the ink transfer, so that the impression is received from the plate cylinder. When a small amount of difference occurs, a ghost image is formed. In this regard, as long as the drum pressure is appropriately reduced and the expansion and contraction coefficient of the blanket is reduced, the failure can be eliminated.
4. The ghost of the blanket is loose or caused by the drum
When the blanket is stretched, the force is not uniform, so that the local position is not close to the surface of the drum, the emptiness or the bad condition of the drum, and the partial multi-layer padding or foreign matter adhesion on the back of the blanket are easy to make. Partial layout imprints. In this regard, the blanket should be loosened for inspection, and the blanket should be tightened after cleaning up the bad phenomenon to eliminate the ghosting failure.
5. A ghost image caused by improper plate or blanket mounting.
When the printing plate or blanket is not clamped, a slight looseness during the embossing process may easily cause a ghosting failure. In this regard, as long as the inspections are taken carefully and the corresponding measures are taken, the ghosting failure can be eliminated.
6. Ghosting caused by abnormal drum press work
When the parts related to the roller clutch pressure are unsuitable or due to wear, a certain amount of difference is generated each time the pressure is pressed, resulting in a ghost image caused by different positions of the print. In this regard, as long as the clutch pressure mechanism is recalibrated and the wear parts are repaired, the drum clutch pressure is accurately, coordinated, and unified, and such faults can be eliminated.
7. The ghosting caused by insufficient pressure on the paper.
When the roller bite is worn and deformed due to wear and tear, the force on the printed sheet is insufficient when the crepe paper is imprinted, so that the printed sheet slips out of the nip in the embossing, and the amount of slip is not the same every time, so that it is printed. At one time, since the fuzzy imprinted on the blanket does not accurately overlap with the re-transferred ink, a ghost image is generated at the mouth. In this regard, the drum should be inspected for teeth, such as uneven force and deficiencies caused by deformation, and should be re-adjusted. If the surface of the crepe paper is worn and the paper is not tight, replace it with a new one to ensure that the paper is not slipped when the paper is jammed, and the ghosting of the sputum can be eliminated.
8. Ghosting caused by looseness of the roller gear or bearing wear
When the printing machine has been used for a long time, the maintenance and overhaul work has been implemented for a long time, so that the roller gear or bearing is seriously worn, and vibration will inevitably occur during the imprinting process, and the ghosting of the imprint will follow. In this regard, the fault should be eliminated after the worn parts are repaired.
9. The ghost of the drum liner is not suitable
When the diameter of the lining of the plate cylinder and the blanket cylinder is too large, the speed difference and the friction are generated due to the inconsistent line speeds during each embossing, so that the surface of the blanket is deformed by being squeezed, and the inner lining material is easily moved. Until the wrinkles, the ghosting of the imprinted ghosts will follow. In this regard, the center distance of the drum should be re-measured, the thickness of the lining should be controlled according to the requirements of the equipment specification, and the linear speed of the drum should be kept consistent to avoid the occurrence of the ghosting fault.
Second, the classification and elimination of horizontal ghosting
1. Ghosting caused by poor quality
When the paper surface is uneven and the raffinate edge is bad, the paper is elasticized during the embossing process, and the paper surface of the bow and the surface of the blanket are slipped to cause a ghosting failure. In this regard, the paper should be subjected to knocking treatment as appropriate, or the upper and lower jaws of the uneven paper surface should be flattened, so as to achieve the effect of eliminating the ghosting of the partial paper surface.
2. Ghosting caused by poor lining
When the rubber liner is covered with too much or under-tightening, and local hollowing, etc., it is easy to cause local lateral ghosting failure. In this regard, the rubber lining should be re-fixed and wrapped, and the fault can be eliminated after eliminating the bad situation.
3. The ghost caused by the axial movement of the cylinder
When the thrust bearing of the drum is worn, or the loosening of the thrust bearing screw occurs, the drum will be easily slipped during the embossing process, and the lateral ghosting of the print is induced. In this regard, the degree of wear of the thrust bearing should be checked and corresponding measures taken to repair it. If the roller thrust bearing is loose, tighten the nut and tighten the screw to prevent looseness. This fault can be eliminated.
4. Heavy shadow caused by excessive backlash and loose mesh
When the gear wears more severely, the phenomenon of shaking will inevitably occur during the imprinting process, so that the previous and subsequent imprints cannot be accurately overlapped, thereby causing lateral ghosting and even vertical ghosting. In this regard, corresponding repair and adjustment measures should be taken to reduce the backlash and reduce the center distance, so that the gears maintain a good meshing state and eliminate ghosting faults.
In short, there are many reasons for the failure of the imprinting ghost. As long as we are good at carefully observing and analyzing the fault phenomenon in production practice, we can handle such faults quickly and well, and ensure the printing quality of the products.