Pre-regulation overprinting is not allowed to exclude faults

Recently, we have encountered an example of longitudinal ghosting on both sides of the J2108 offset press. Re-checking and adjusting the handover relationships of the machines will not help. There are many reasons for the inaccurate overprinting at both ends of the former. There are mechanical, printing processes, paper, etc. After eliminating the following factors, the problem is still concentrated on mechanical factors.

After a period of time, it was found that when the paper was positioned on the paper feed platform, the drop of paper was just ready to pick up the paper, and the paper had to bounce back a few times before it was handed over to the printing area. Is it always when the paper is positioned on the table? Is it due to the fact that the paper-tooth gap is smaller than the gap between the table surfaces and is touched by the dental pad? Is it due to other reasons? Using a feeler gauge to check the gap between each passing tooth pad and the tooth base one by one, the gap is in line with the requirements (that is, the gap is three or four times the printed paper), the paper transfer time is also correct, is the tooth surface too Is it skewed, causing the paper-tooth sheet to crack and hit the paper? We also adjusted the paper pad, and the problem was not solved.

After careful observation, it was found that the paper-handling teeth were not located at the lowest position of the paper-transmitting tooth holder due to the delivery of the paper-handling teeth. Although the longitudinal paper was held against the inner side of the two wallboards, the vertical paper-holding position was fixed, but the paper-handling teeth were fixed. The two eccentric magnets of the shaft always perform uniform motion. When the paper drop teeth want to close the teeth, because it is not at the lowest point, this time the teeth in the movement did not completely close the teeth and touch the mouth of the paper, the paper will be hit back and forth, causing The process of paper picking is not stable, and paper is transported into the paper to hit the paper during the movement, so that the degree of insulation is not the same, that is, the number of paper is inconsistent, resulting in irregular registration at both ends of the front printing gauge, longitudinal weight Shadow phenomenon.

According to the requirements, the paper handing is in the position of 76-78 degrees. When the center of the eccentric shaft of the paper-handling tooth and the middle point of the paper-gripper tooth are in a straight line, the instantaneous speed of the paper-removing tooth is zero, which is for the paper picking. The best moment. However, the scale of the J2108 offset press used by us is related to the actual mechanical action. Therefore, the actual operation relationship of the machine shall prevail in the adjustment. We adjusted the closing time by 3 degrees to 5 degrees in the positive direction, that is, the closing time was about 72 degrees. At this time, we are in the best gripping state, that is, the center of the eccentric shaft of the paper delivery, the center of the gripper tooth, and the mouth of the gripper. Point in a straight line. After adjusting and then feeding, observe that the paper will not bounce on the dental platform, and the printed products will not be duplicated in the longitudinal direction and the overprinting will be accurate.