Paper wrinkle troubleshooting

Paper wrinkle is one of the common faults in the production of sheetfed offset presses. There are many factors that cause paper wrinkles. They can be roughly classified into two types: one is caused by a machine; the other is caused by paper. Wrinkles caused by the machine are generally easy to remove, but due to the paper's own factors, such as when the paper moisture content is too large, too small or uneven, the formation of tight edges, flounces, curls and other uneven papery (paper The phase refers to the wrinkles caused by the shape of the paper with a certain water content at a certain temperature and humidity, and it is not easy to solve. Most small-scale book printing companies cannot control the temperature and humidity of the workshops and warehouses within the proper range due to limitations on plant, equipment, and funds. Therefore, paper crease failures due to the impact of climate change on paper are caused. It will increase greatly. If these failures cannot be eliminated in time, it will affect the equality of the halo process, delay the delivery time, and cause the manufacturers and customers to suffer losses.
In a J2101-A offset press production, a paper wrinkle defect occurred and wrinkles occurred at the tip of the paper. We turned the paper around and tried it. The wrinkles were always on the same side, so the paper itself caused it. After turning the paper back and forth to try it out, the wrinkle failure disappeared. Through careful observation and comparison, we found that one side of the front and back sides of the paper is relatively straight, and the other side has a severe tight edge phenomenon (means that the paper is stored in a warehouse where the humidity of the environment is less than the humidity of the paper, and the edge of the paper is partially dehumidified faster than the middle portion. Dehumidification also occurs due to the shortening of the edge of the paper in the middle.) Therefore, all of us use the straighter side to make a mouthwash, and the side that has serious tight edges is used for dragging. In this way, printing is turned on. The failure has not occurred for a while, but the boot time is not long, and wrinkle failure has occurred again. This time, the paper has relatively serious wrinkles on both sides of the tip, so that there will be many waste products and the loss will be too great. An inspection was stopped and it was found that there was a lotus leaf on the straight side. Nguyen's and Feng's have been ruled out; the electric heater is used to bake the left and right sides of the paper, and the fault still exists. We analyze: because the humidity in the workshop is greater than the humidity in the warehouse, the relatively flat side was in the middle of the paper before cutting. After cutting, the moisture absorption speed on this side is faster than the middle part, and the moisture absorption amount is also greater than the middle part. In part, a large amount of moisture causes the edge of the paper to stretch and form a flounced edge. When printing, the creases of the paper are unavoidable because the edges of the crepe are not straight.
Because customers are eager to get goods and they cannot change paper, production cannot stop. At this point we thought of another fault: In one production, the machine suddenly appeared to be unable to move some of the problems. At first, it was thought that there was no pull on the side scales. After each time the side scale was pulled, it was thought that it was a lack of pull on the side scale or the paper was too far away from the side scale. After adjusting the paper and increasing the pulling force of the side gauge, there was still Some paper did not pull. Check the slow speed and found that the upper gauge of the front gauge on the other side of the working side gauge holds down the paper, that is, the gap between the front gauge and the roller surface is too small, and the friction between the paper and the front gauge and the drum surface is too small. Increased, the increased friction sometimes can not be overcome with the lateral pull, so when the side guide does not move the paper, the clearance between the front gauge and the roller surface (the gap is below 80g/cm2 When the paper is generally three sheets of printing paper, the size of the paper is increased, and the problem is solved.
So, can we use Dado to increase the friction between the paper and the gauge on the front gauge and the roller surface to overcome the failure caused by the paper's leaf edge? With this in mind, we decided to give it a try. We adjusted the clearance between the front gauge and the drum surface to a thickness of the printing paper (note that only the front gauge, which is far from the working side gauge, should be adjusted). In order to prevent the paper from getting in place at the front gauge, we added pressure on the platen, increased the pulling force of the side gauge, and adjusted the timing of the side profile so that the side gage was only put in at the moment the carious teeth had just creped. Paper (be careful not to interfere with the accuracy of the side gauze). After everything is tuned, the printer is turned on and printed, and there is still a small wrinkle on one side of the paper. We tried to adjust the wrinkled side of the paper to the side of the tusks, make it more tight, wrinkles increase, relax, wrinkles disappear.
From this we conclude that in this failure, the main cause of wrinkle failure is that the tusks do not reach the straight edge of the paper. Therefore, we use the friction between the paper and the front gauge and the roller surface and the pulling force of the side gauge to straighten the squeak edge, so that when the enamel is creased, the edge of the paper is straight and the fault is eliminated. .