Analysis of the causes of fat nails in the most po

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Analysis of the causes of fat nails in tin printing

if from the perspective of lithography, iron and paper are the same type of printing, then the quality defect of "fat nails" is unique

"fat nail" is also known as "nail protrusion". The so-called "fat nail" refers to the nail like protrusion on the printing surface of the sheet due to hard blocks such as garbage particles on the back of the sheet during the normal iron printing process (see the schematic diagram). In serious cases, this kind of nail like protrusion is scattered and dense; In many cases, there are only a few "fat nails" on the whole printing sheet. However, in any case, the existence of "fat nails" has brought serious harm to the quality of iron printing products. At least, it will affect the appearance effect of products, and at worst, it may cause the whole batch of products to be scrapped

as the "fat nail" can't be cured for a while, the iron printing industry generally feels very thorny about this quality defect. The author believes that for iron printing enterprises, in order to eliminate the disadvantages of "fat nails", the focus should be on the system cleaning and maintenance of the machine operating surface, which is conducive to finding out the crux of the disadvantages of "fat nails". Otherwise, the dirt or debris on the operating surface of the machine will be mixed with the disadvantages caused by non-standard operation, and it will be difficult to find the key point to solve the problem. Based on the author's long-term practical experience, this paper will put forward some simple views to solve the disadvantages of "fat nails", for the reference of operators in the iron printing industry

according to the location of "fat nail", the disadvantages of "fat nail" are divided into fixed position and unfixed position, which are introduced respectively below

first, the phenomenon of "fat nails" in fixed positions

because the disadvantage of "fat nails" is that there are nail like protrusions on the printing surface, skilled operators usually can easily judge that there are garbage hard blocks on the embossing cylinder. If a "fat nail" is found in the fixed position (at the same part of each printing sheet) during the production of iron printing, it indicates that the surface of the embossing cylinder is indeed stuck with garbage lumps. Because the embossing cylinder is a steel structure, its hardness is far greater than that of garbage hard blocks, and the hardness of these hard blocks often exceeds the hardness of the blanket, resulting in the process of iron stamping, the printing sheet can only protrude in the direction of the blanket, so the result is always a protruding "fat nail" on the printing surface

next, let's analyze why Eastman Chemical is produced on the surface of the embossing cylinder, so that the dry diaphragm produced by s company can also ensure high strength. At the same time, tritan MXF 121 (copolyester) produced by s company: in addition to good toughness and durability, there are garbage hard blocks in fixed positions, and why do these garbage hard blocks stick to the embossing cylinder

under normal circumstances, the garbage lumps on the imprint cylinder are mainly caused by insufficient cleaning and maintenance of the equipment, especially when the transmission part is adhered with oil dirt. If there is garbage entering, it is easy to bring the garbage to the surface of the imprint cylinder through the continuous transmission of the tin sheet, and adhere to the imprint cylinder through the effect of the iron pressure. In this way, the phenomenon of "fat nails" in fixed positions is formed

to solve this problem, we should be targeted, that is, check whether there are garbage lumps on the surface of the imprinting cylinder after shutdown. When checking, you can take the printing sheet for comparison and see where the specific part is. Then find the hard block adhered to the imprint cylinder and completely remove it. In this way, the disadvantages of "fat nails" in fixed positions can be eliminated immediately

second, the phenomenon of "fat nails" with unfixed positions

in daily production, the phenomenon of "fat nails" with unfixed positions is more common, and the reasons for this disadvantage are relatively more complex, but generally speaking, it is no more than the following three situations

1. The iron printing equipment is not clean enough, and the garbage falls on the impression cylinder.

the iron printing equipment is not clean enough, and the garbage falls on the impression cylinder, which will make the tin plate printing sheet subject to the impression force between the rubber cylinder and the impression cylinder. Because there are hard objects on the back of the printing sheet, the printing brush of the printing sheet is forced to protrude in the direction of the blanket, forming a "fat nail". Because the viscosity of this kind of garbage hard block is low, it cannot be firmly adhered to the imprint drum, but moves its position with the continuous operation of the iron printing equipment, so the position of this kind of garbage hard block is not fixed, which is reflected in the printing surface, and the position of "fat nail" is also constantly changing

the solution is to thoroughly clean and maintain the iron printing machine to avoid the phenomenon of "fat nails" caused by garbage falling from the equipment due to poor cleaning

2. Careless operation causes garbage to fall onto the embossing cylinder

there are many opportunities for garbage to be brought between the cylinders in the iron printing operation. When calibrating the ink bucket, when pouring the ink in the ink bucket into the ink bucket, avoid dropping the garbage on the ink knife or the belt on the ink bucket, so as to prevent the garbage from adhering to the conveyor belt, and pass the garbage into the rollers through the transmission of the conveyor belt. In addition, when checking the edition, changing the blanket, cleaning the water roller and ink roller, it is also necessary to avoid bringing garbage

if the operation is improper, the garbage brought in will fall on the embossing cylinder, and the printing surface of the printing sheet will inevitably produce "fat nails". Because the garbage that causes this kind of "fat nails" has poor adhesion and will be taken away by the printing sheets, the "fat nails" produced have no fixed position

to solve the "fat nail" defect of the electro-hydraulic servo material testing machine caused by improper operation, we must first standardize the operation process and try to avoid bringing garbage to the conveyor belt. Always clean the transmission mechanism, including the side gauge, toothing mechanism and other parts. No garbage and dirt are allowed. If garbage is found, it must be removed in time. In this way, we can avoid the "fat nails" caused by improper operation

3. The garbage on the printing sheet is transferred to the impression cylinder

the garbage on the printing sheet comes from the quality defects of the sheet itself, such as poor surface quality of the sheet, sand inclusion and other defects, or dirt. The second is the paint iron. Coated iron is a tinplate coated with white paint or other internal and external paint. Sometimes, the paint will fall off because of too tight teeth; Some coatings have poor adhesion, and paint particles often fall off at the edge of the coating iron. The third situation is that the proofreading iron is not properly protected, and the surface area has dust and debris

the above three kinds of garbage particles brought by the tin sheet itself will be transferred into the drum during the continuous input printing process. Before starting, check whether the oil circuit from the oil tank to the oil pump is connected. If it is attached to the embossing drum, it is easy to produce "fat nails" when printing iron. Most of these "fat nails" are "fat nails" without a fixed position

solutions must also be targeted. If the plain iron itself has defects, the sheet must be replaced and reprinted, or the disadvantages of the sheet itself must be explained to the customer in advance. If it is brought by the paint iron, it is necessary to distinguish whether it is too tight in its teeth or the paint itself has quality problems. If you bite your teeth too tightly, you can adjust it until the tightness is appropriate. If there is a problem with the coating, it is necessary to re select the coating with relatively strong adhesion to prevent the coating on the iron edge of the coating from falling off particles after drying. If it is caused by garbage attached to the calibration iron, the surface of each calibration iron must be cleaned. First, stack the plates neatly, and then cover them with a thick cardboard to avoid the accumulation of garbage on the surface; For the calibration iron used in the machine, each piece must be wiped before the machine, and no dust particles can be left

in a word, the "fat nail" defect is a major defect affecting the quality of iron printing, which must be solved from the root, so as to fundamentally eliminate the "fat nail" which is a very harmful quality defect

Shanghai Meilin can making Co., Ltd. Wang Haohao

source: printing technology - packaging and decoration printing

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