Causes of Paper Folding in Offset Printing and Handling Methods (Continued)

3. For typographic printing presses, due to improper use of the machine, adjustments caused by improper adjustment of the paper are very common, and the following five types (Figures 1 to 5) are generally pleated. The following are the specific analysis of the causes and treatment methods. . The reason of Figure 1 is as follows: 1 The pressure on the impression cylinder is too low. 2 The oscillating tooth pads are uneven. 3 pressure foot too strong. 4 The brush wheel and line belt are under too much pressure. 5 Paper is uneven. Treatment methods: 1 Because the impression roller is too light, and even if it can't hold the edge of the paper, the phenomenon of Figure 1 will appear, as long as the light teeth can be adjusted, if adjusted To come, it is the elastic failure of the gingival spring. After replacing the gingival spring, it can be re-adjusted. 2 The oscillating jaw pad is uneven, so that the edentulous teeth on the impression cylinder are not in a straight line but a wavy curve when the oscillating tooth is attached to the oscillating tooth. Therefore, the phenomenon shown in FIG. 1 occurs. The processing method is to process the dental pad, or to replace the new dental pad, reinstall, and adjust the whole, the problem will be solved. However, it is necessary to note whether overprinting is not accurate after starting up, and it is not allowed to re-adjust the overprinting rules. 3 The presser foot is located in the center of the paper edge. When the air flow is too strong, the paper will bulge too much along the direction in which it blows. Such a paper will produce the phenomenon shown in Fig. 1 when passing through the impression cylinder. Especially when printing thin paper, it is more obvious, and the requirement for the pressure of the presser foot is even stricter. The solution is to reduce the pressure of the presser foot, but not too small, otherwise the paper will not be separated and there will be a printing failure. For different grams of paper, the size of the pressure foot air flow is also different and must be treated differently. 4 The brush wheel is mounted on the belt and rotates with the friction force of the belt. When the pressure on the belt is too high, the paper will still have a large forward momentum after reaching the front gauge. And continue to move forward, causing the middle of the paper to bulge. Swinging the teeth to catch the paper will result in the phenomenon shown in Figure 1. The processing method only loosens the brush wheel adjustment screw to make it produce friction with the paper tape. You can put the paper into the front gauge without causing the paper to bulge behind the front gauge. For printing different grams of paper, the pressure on the brush wheel must also be adjusted separately. 5 The paper edge is not in a straight line and it is a convex curve in the middle. When the impression cylinder rubs against the paper, it will produce the phenomenon of Figure 1, the solution is to see if the paper edge on the other side of the paper is straight, Just use the other side of the paper as a paper edge, otherwise you will need to reprocess the paper or change paper for printing. Figure 2 shows the reasons: 1 side pull gauge does not match with swinging molars during working hours. 2 The pressure on the side of the impression roller is too light. 3 The edge of the paper is not caught on the side of the paper. 4 The paper curled up causing the imprint to roll and the teeth are not good. Treatment method: 1 side pull gauge is to close the paper immediately after entering the front gauge to position the paper, and then immediately before swinging the enamel pick paper, the side pull gauge opens. The machine continues to perform these actions in a consistent and continual manner. Any one action will lead to paper failure sooner or later, especially when the side pull gauge is still positioned sideways. If it is not fully opened, the oscillating teeth will weigh the paper. Embossing rollers form "grabbing paper". The phenomenon of Figure 2 will result. The solution is to first observe it repeatedly and determine whether it is the time for the side pull gauge to operate late, or whether the swinging gum is timed earlier, and then decide which part to adjust, and then adjust it repeatedly after the determination. 2 If the pressure on the side of the embossing cylinder is too light or it cannot be stopped at all, the phenomenon shown in Figure 2 will occur. The solution is to adjust the pressure of the cavities. 3 There are many reasons why the side of the paper is not being choked: ● Because of the improper position of the pull tab, when the paper is positioned sideways, the paper edge of the paper is moved under the paper feed table so that the swinging tooth will not reach this position. Side of the paper produces the phenomenon of Figure II. ● The phenomenon of Figure 2 is caused by the oscillating tooth or the impression roller being too loose. ● Because the pressure on one side of the brush wheel is too light, the enamel does not reach the side of the paper edge, and so on. The solution is to first look at the paper path and analyze which part of the edge of the edge of the paper has not been twisted. Adjust it. ● Due to the quality of the paper itself, the ills of storage, or the fact that the amount of water used has been controlled too large when printed, the two corners of the paper are upturned. Phenomenon, as long as the paper to deal with anti-warping can be resolved. Reasons for Figure 3: 1 side pull gauge does not match with swinging molars during working hours. 2 paper deformation around (commonly known as tight edges). Treatment method: 1 is similar to the first reason shown in Figure 2, except that when the pendulum is pressed, the side tension gauge has not been completely opened. Perhaps it is only a little bit worse, but it is this point that will cause the paper to produce Figure 3 shows that the relatively high number of papers (such as 105g and 128g art paper) often does not show up, and papers with relatively lower number of grams (such as newspapers, 55g, etc.) ignore this part. The judgments are therefore more detailed when adjusting the time. 2 There are the following ways to deal with tight edges: ● The paper is placed in the workshop or warehouse for a period of time to allow the humidity of the paper to naturally balance with the outside world. The effect is good, but this method requires a certain amount of space and time. ● Sprinkle some water around the pile of paper, or spray directly on the edges of the paper with a simple spray so that the “tight edges” absorb water and reach the paper surface. However, this method is not very good and the effect is not ideal. ● Re-hanging the paper, while blowing, about 5h or so can make the paper basically balanced moisture content, paper formation. ● Knocking on tight-edge paper may have a certain effect. Figure 4 shows the reason: The middle of the impression cylinder is not well or does not hold the paper at all. Treatment method: 1 It is more common that the middle caries of the impression cylinder are worn, and the teeth are flattened. If the printing ink with a relatively thick ink color, it needs a relatively large peeling force to peel off the paper from the rubber roller. If the tooth pad has no teeth, the friction force is small, so that the middle part of the paper slides out from the cavities. After passing through the printing section, the failure of Figure 4 will occur. There are two ways to solve this problem: The first is to properly add a detackifier to the ink to reduce the viscosity of the ink. The second is to use the alloy knife to draw some diamond lattices on the surface of the flattened tooth pad. The deeper the better the grid. 2 The middle cavities are so loose that the blemishes are not good or can't reach the paper, resulting in the phenomenon of Figure 4. Just tighten your teeth. The reason for the appearance of Figure 5 is as follows: 1 The suction of moisture around the paper produces a "foliar edge". 2 The surface of the impression cylinder is “stacked”. 3 Imprinting roller squeezing tooth spring fatigue failure. Treatment method: 1 The production of "foliage" indicates that the water content on the four sides of the paper is larger than the center part. It is possible to perform a knocking process on the edge of the lotus leaf. There may be a certain effect. If it is still unsolvable, the following three methods are used: ● Rehanging the paper once again and performing the air blow. The overall water content of the paper tends to be even and balanced with the humidity of the surrounding environment. ● Use "infrared dryer" to bake the "foliage". ● Stack the entire stack of paper into the baking oven to reduce the moisture content around the paper. The edge of the paper tightens and the "foliage edge" disappears. However, the latter two methods must strictly control the baking time. If the baking time is too long, it will result in the phenomenon of tight edges mentioned in the previous paragraph. 2 In the case of two-sided printing with a large amount of printing, when the one side is printed, the other side is printed. At that time, the ink on the first side of the ink will gradually accumulate on the surface of the imprinter, and the accumulated thickness will be a certain degree. The uneven surface of the impression cylinder will cause the phenomenon of the paper to produce Figure 5. The solution is to control the surface first. Ink volume, not too large.Timely scrub the impression cylinder.3 Impression roller 叼 The use of teeth for a period of time will lose their elasticity due to fatigue, resulting in the phenomenon of Figure 5. The solution is to replace the gingival spring and readjust it. Causes the printing trouble of the paper to wrinkle, analyzes the different reason that produces, take corresponding measures to solve.Prints strictly according to the correct printing craft to operate in the printing, observes carefully in the work, unceasingly summarizes, accumulates, causes the paper to pleated Factoring before printing can fundamentally eliminate paper pleating G. (Author: Tianjin Rifa Printing House, Tianjin Institute of Light Industry) Editor/ Ou Ding military