Impression of Imprinting in Indian Iron Causes Overcoming Reasons

At present, most of the metal plate offset presses used by our metal packaging companies are two-color machines. High-speed four-color machines and six-color machines are also printing iron production in some companies. Only a very small number of monochrome machines are still in service. Regardless of the model, if it is not taken care of in the process of production preparation or improper adjustment is made, it will cause overprinting in the printing iron production. From the production practice, it can be seen that the reasons for overprinting do not come from many aspects, so we should also analyze it from all levels.

First of all, we look at the original version, that is, electronic color separation film or photochromic film itself has overprinting errors. There are many factors that can cause the dichroic sheet overprinting. In general, there are operational reasons and equipment reasons. Then the uneven tension and deformation of the printing plate in the on-car school printing operation will also lead to the misprints of overprinting, mainly due to the variable size of the pulling force. In addition, the rubber roller liner can also cause overprint errors. Therefore, most printing companies have a clear set of standards for blankets, so that overprinting due to unreasonable blankets can be avoided. From the point of view of the blanket itself, poor quality blankets are often poorly elastic and easily deformed, which can cause overprinting errors. Printing machine adjustment is the highlight of overlay error. First of all, the precision of the printing machine parts is better. According to the requirements of the printing iron, the first printing plate must be set with a crosshair, and the subsequent plate crosshairs coincide with each other. The following principles should be mastered during the adjustment: 1. The gear positioning force should be able to stretch and fall, and it is easy to adjust; 2. The position of the printing plate adjustment direction should strive for consistency; 3. The method of loosening and pulling should be adopted for the school edition to prevent excessive force. From the disadvantages of the folder and deformation; 4, plate adjustment should be ahead of some adjustment, in order to give the printing plate and roller attached to the margin. There are two requirements for side-gauge adjustment: First, the strength of the spring should be properly adjusted according to the thickness of the metal sheet; secondly, the distance between the gauge line and the metal sheet is usually controlled at 4-5 mm.

Secondly, in the printing iron, three rollers under the action of mechanical force, the overprint due to pressure changes is not allowed, we call the general overprinting is not allowed; some parts of the printing machine in the operation of the printing machine damage and improper operation caused by overprinting Not allowed, we call it a special overprint.

The general overprinting is not allowed, which refers to the “pull-up” phenomenon caused by the pressure change of the three rollers in the printing machine. The so-called "pull up" means that the plate cylinder is cushioned and the rubber cylinder is cushioned and the impression cylinder is equal to the diameter of the impression cylinder. The reasons for the “pull-up” are: 1. The change of the printing plate cylinder or blanket cylinder liner changes the pressure; 2. The blanket quality is poor and the elasticity is poor. When “pull up” occurs, proper adjustments to the plate liner and blanket liner should be made.

Particular overprinting is not allowed. It mainly refers to the overprinting caused by the wear or malfunction of the upper parts of the iron printing machine. Can be summarized as follows: 1, improper installation of printing plates or blankets; 2, spring push head and push pull rules and spring elasticity is not appropriate; 3, dental care cooperation is not coordinated; 4, dental care and clips are not engaged reasonable.

Blanket factors are not allowed to be overprinted, and overprinting of graphic and graphic prints is not strictly related to the elongation of the blanket. There are two reasons for the deformation of the blanket: 1. The size and direction of the friction when the blanket is in contact with the printing plate and the metal sheet; 2. The elongation of the blanket. The friction force is the same in size and direction, the blanket has different elongation, and the degree of deformation is also different. This is related to the inherent quality of the blanket and its degree of tightening during operation. Under normal circumstances, the blanket stretched tightly and the elongation was small, and the change of blotting was not significant; the elongation was large, and the imprint pattern was likely to have a phenomenon of “reprinting”. Therefore, the quality of the blanket or the same blanket, due to the difference in tension when the installation of the printing effect is not the same. The following points should be noted when installing the blanket: (1) The blanket is required to have characteristics of small elongation. (2) After the blanket is tightened, it is generally not allowed to change it arbitrarily to ensure the accuracy of overprinting.

Variations in plate thickness and thickness of the plate, as well as flatness, affect overlay accuracy. The plate used in the printing plate is aluminum, and its nature is soft. Generally, it will produce tensile deformation after installation, affecting the accuracy of overprinting. Tensile deformation of the printing plate: Under the action of tension, the plate has a positive relationship between the elongation value and the tension and length, and has an inverse relationship with the sectional area and elasticity. In other words, the length also becomes larger; the smaller the elongation, the larger the cross-sectional area and the elasticity coefficient. Practice has proved that when the blanket is installed, attention should be paid to the latitude and longitude direction to prevent the radial direction from parallel with the axis of the drum. The plate itself is fixed on the plate cylinder by pulling force, and its aluminum elongation will inevitably change. However, the larger the tensile force, the greater its elongation. Therefore, during the installation, to minimize the repeated tension, but the force should not be too large, generally controlled in the plate and the plate roller adhesion is appropriate. In addition, there must be an accurate judgment of the previous rules, and the smaller the error, the better. This maintains the stability of the printing plate, that is, the rules are mastered and adjusted within the minimum range. In addition, the longer the length of the plate, the greater the value of the elongation, especially in the printing of larger size products, the length of the plate used in the larger, the installation must take into account the change in elongation. Secondly, the thickness of the plate may not be the same, which means that the plate with a large thickness must have a large cross-sectional area. Under the condition that the elastic coefficient is not changed, the value of the surface tension of the printing plate will not change. Then for a given pull, the greater the thickness of the plate, and its correspondingly small elongation value, these basic knowledge should be clear to the print iron construction personnel. Another reason for misregistration is the deformation of the plate. The printing plate is firstly subjected to a pulling force when it is mounted on the drum. However, when the points of force are dispersed, part of the force will be converted into positive pressure on the printing plate. In addition, the printing plate shifts during the calibration of the side gauges, which has a frictional force with the drum surface, and its degree of stretching is also related to the included angle of the drum. The small radius of the printing machine drum, then its angle is large, the printing plate is stretched; Conversely, if the roller radius is large, the included angle is small, and the possibility that the printing plate is stretched is small.

In short, the inaccuracy of overprinting in the construction of printing iron is one of the quality issues that must be taken seriously in printing iron production. Iron-plated operators must strictly implement the technology during construction, strictly select materials and perform strict construction, so as to ensure the quality of the printed iron products and prevent adverse consequences caused by the “overprinting”.