Analysis of ghosting failure of the hottest offset

2022-08-22
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Analysis of ghosting failure of offset press

not long ago, ghosting occurred in the printed matter produced by an offset press in a unit. At that time, we stopped the machine immediately to conduct a comprehensive inspection of equipment and materials. Through the investigation, it was found that the plate was pulled too tight during the last version, and the high-speed operation of the machine made the printing plate tighter and tighter. Finally, the printing plate broke near the plate clamp, and the sensitivity of the detector would drop and crack. Due to the looseness of the printing plate, the pictures and texts transferred to the blanket are unstable, which are reflected on the substrate, forming ghosting. After finding the cause, replace the printing plate, and the fault is quickly eliminated

ghosting is an important factor affecting printing quality, and its causes are diverse. In general, it can be summed up in the following three aspects: first, the parts of the printing equipment are not well matched; Second, improper operation methods; Third, the printability of printing materials is not good. The following is an analysis of several situations that are easy to cause ghosting failures

Liu Zhongfan said: "I don't doubt the prospect of graphene industrialization. 1. The rubber layout department or the whole sheet is not tightened. If you use the old blanket, tighten it once, while the new blanket needs to be tightened twice. That is, after the first tightening, operate 100 ~ 200 revolutions and then tighten it again, so as to prevent it from producing stress relaxation and causing ghosting after the first tightening.

2. The printing plate is not tightened. Ghosting in this case is generally manifested in leaning over or On the outside side. At this time, just tighten the printing plate again and clean the blanket

3. The color sequence of multicolor machine printing is not arranged properly. In multicolor printing, the text version should usually be placed in the last color deck, and the ink viscosity of the color deck should be adjusted appropriately. Otherwise, part of the ink on the substrate is easy to be transferred to the blanket, and is transferred to the substrate for a second time, forming ghosting

4. The size of plate cylinder and cylinder lining is unreasonable. This will inevitably lead to some differences between the deformation of the blanket when it receives the pictures and texts from the printing plate and the deformation when it transfers the pictures and texts to the substrate, which is a necessary detection instrument for the R & D and quality inspection of hinge manufacturers and finished product manufacturers, resulting in ghosting

5. The printing pressure is too high. When the printing pressure is too large, the blanket will have a large degree of deformation, causing the displacement of graphics and text in the transfer process, resulting in ghosting

6. Ink drying is not good. Especially in the wet press wet printing state, the front color printing ink on the substrate will be transferred to the surface of the next group of blanket under the printing pressure, causing ghosting. This kind of ghosting is mostly chaotic. In such cases, it is necessary to improve the dryness of the ink or enhance the absorption of the paper to the ink

7. Use different batches of paper. Because different batches of paper have different telescopic characteristics, it is easy to cause disordered ghosting failure

8. The paper is uneven. This kind of ghosting mostly occurs at the trailing tip of the paper, on both sides of the trailing tip or in the middle of the paper

9. The equipment is old and the fitting clearance is too large. The higher the printing speed, the more serious this kind of ghosting phenomenon

10. The clutch pressure mechanism is not adjusted well. If the market is worried about the shortage of raw materials, the parts of the clutch and pressure mechanism are not closely matched, there will always be fourorfive prints that will be ghosted every time the machine is turned on

11. The printing cylinder moves axially. This situation will produce horizontal ghosting, and the ghosting phenomenon is generally serious, so the equipment should be repaired in time

12. The clamping force of the impression cylinder is inconsistent or insufficient. This will make the substrate transfer unstable, causing partial or full version ghosting

of course, ghosting failure is not limited to the above situations, but also due to other reasons. This needs further exploration in our work, so as to better eliminate the phenomenon of ghosting and improve the printing quality

source: Printing Technology

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