Causes of fat nails in tinplate printing

If we say that from the point of view of lithography, printing iron and printing paper are the same type of printing, then the "fat nail" quality defect is unique.

"Fat nails" are also called "nails." The so-called "fat nail" refers to the back of the tinplate sheet due to the presence of debris such as litter, resulting in the normal printing process, tinplate printing surface spikes appear (see schematic). In severe cases, the spikes are dotted and dense; in many cases, the entire print has only a few "fat nails." But in any case, the existence of "fat nails" has brought serious harm to the quality of Indian iron products, and has affected the appearance of the products. It may seriously cause the entire batch of products to be scrapped.

Due to the fact that "fat nails" can not be eradicated, the printing iron industry is generally very troubled by this quality defect. The author believes that for Indian Railway companies, to eliminate the drawbacks of "fat nails", the key is to do a good job of cleaning and maintaining the system's operation surface. On this basis, it is helpful to find out the crux of the "fat nails." Otherwise, if the dirty or crumbs on the operation surface of the machine are mixed with the ills caused by non-standard operation, it will be difficult to find the key point to solve the problem. Based on the author's long-term practical experience, this article puts forward some simple opinions on solving the ills of "fat nailing" for the reference of operators in the printing industry.

According to the position of "fat nails", the disadvantages of "fat nails" are divided into fixed and unfixed positions. The following are introduced respectively.

First, the fixed position of the "fat nail" phenomenon

Due to the appearance of "fat nails", nail-like protrusions appear on the printed surface, so skilled operators can easily determine that there are rubbish lump on the impression cylinder. If a fixed position (in the same part of each sheet) has "fat nails" during the production process of the printed iron, it is indeed the surface of the impression cylinder with rubbish lump. Because the impression cylinder is a steel body structure, the hardness is far greater than that of rubbish lump, and the hardness of these lump often exceeds the hardness of the blanket, so that in the imprint process of iron printing, the printed sheet can only protrude toward the blanket direction, so the result is always Prominent "fat nails" on the printed surface.

Next, we analyze why there is a fixed location of rubbish on the surface of the impression cylinder. Why does this kind of rubbish stick to the impression cylinder?

Under normal circumstances, the rubbish lump on the impression cylinder is mainly caused by insufficient cleaning and maintenance of the equipment, especially when the transmission part is covered with oil. If there is any garbage, the tinplate can be easily transported to the trash after it is transferred continuously. The surface of the impression cylinder is adhered to the impression cylinder by the effect of the printing iron pressure. This creates a "fat nail" phenomenon in a fixed position.

To solve this problem must be targeted, that is, check the surface of the impression cylinder after the machine is shut down for rubbish lump. When checking, you can take a printed sheet for comparison and see where the specific area is. Then find the hard block attached to the impression cylinder and remove it completely. In this way, the "fat nail" malady in a fixed position can be immediately eliminated.

Second, the position is not fixed "fat nail" phenomenon

In daily production, what is more common is the phenomenon of "fat nailing" where the position is not fixed. The causes of this malady are relatively more complicated, but overall, there are nothing more than the following three situations.

1. Imprinting equipment is poorly cleaned, and the waste lands on the impression cylinder

The iron printing equipment is poorly cleaned, and the rubbish lands on the impression cylinder, so that when the tinplate print is subjected to an imprinting force between the blanket cylinder and the impression cylinder, a hard object is pressed on the back of the printed sheet to force the printing of the printed sheet to protrude toward the blanket direction. The formation of "fat nails." Due to the low viscosity of such a lump, it cannot adhere firmly to the impression cylinder, but moves along with the continuous operation of the printing equipment. Therefore, the position of the rubbish is not fixed, but is expressed in printing. On the surface, the position of "fat nails" is constantly changing.

The solution is to thoroughly clean and maintain the iron printing machine and avoid the “fat nailing” phenomenon caused by poor cleaning and dropping of garbage from the equipment.

2. Inadvertent operation causes the trash to fall onto the impression cylinder

In iron printing operations, there are many opportunities for trash to be carried between rollers. When the ink fountain is in school, when the ink in the ink tank is poured into the ink fountain, the rubbish on the ink knife or the ink tank should be prevented from falling down to prevent the rubbish from adhering to the conveyor belt and transferring the rubbish into the drum through the transmission of the conveyor belt. between. In addition, when school editions, changing blankets, cleaning water rollers, and ink rollers, it is also necessary to avoid getting into the trash.

If it is not handled properly, the entrapped trash falls on the impression cylinder and the printed surface of the printed sheet will inevitably produce "fat nails". Because the rubbish that causes this type of "fat nail" has poor adhesiveness, it will be taken away by the printed sheet, so the "fat nail" malady that is produced has no fixed position.

To solve the problem of "fat nailing" caused by improper operation, we must first standardize the operation process and avoid garbage as much as possible on the conveyor belt. It is necessary to clean the transmission mechanism regularly, including side gauges, jaw mechanisms, etc. It is not allowed to have dirt and debris. If any garbage is found, it must be promptly removed. In this way, it is possible to avoid the "fat nail" malady caused by improper operation.

3. The waste on the printed sheet is transferred to the impression cylinder

The rubbish on the printed sheets is derived from the quality defects of the tinplate, such as: poor surface quality of tinplate, defects such as sand inclusion, or entrained dirt. Followed by the coating of iron. Paint iron is tinplate coated with white paint or other interior and exterior paints. Sometimes, because the tusks are bitten too tight, the paint will fall off; some paints themselves have poor adhesion, and the paint granules often fall off at the edge of the paint. The third situation is the improper protection of the school plate iron, and the surface area has dust and crumbs.

The above three kinds of garbage particles brought in by the tinplate stamp itself, in the process of continuous input printing, these lumps of hard particles will be transferred into the drum, if attached to the impression cylinder, it is easy to produce "fat nails" when printing iron. The drawbacks are that most of these "fat nails" have no fixed fatal defects.

The solution must also be targeted. If it is defective, it must be replaced by tinplate or printed in advance to the customer to explain the drawbacks of tinplate itself. If it is caused by coating iron, it is necessary to first distinguish whether the teeth are too tight or whether the paint itself has quality problems. If it is too tight, it can be adjusted until the elastic fits. If there is a problem with the paint, it is necessary to reselect the paint with a relatively strong adhesion so as to prevent the paint on the edge of the paint from drying out and peeling off the particles. If it is caused by the rubbish on the school plate iron, the surface of each school iron must be cleaned. First of all, the reactor should be neatly stacked, and a thick paperboard should be placed on it to avoid accumulation of garbage on the surface. For the school's version of the iron used on the machine, each one must be cleaned and then on the machine, leaving no dust and debris.

In short, the drawback of “fat nailing” is a major drawback that affects the quality of Yintie’s iron. We must start from the root to solve it, so that we can fundamentally eliminate the “massive nail” that poses a serious harm to the quality.