Analysis and solution of flexographic printing quality problems (III)
bars are also called ink bars. The symptoms are relatively simple, that is, the marks perpendicular to the printing direction with the gear pitch dimension as the equidistant mark
bar is mainly caused by gear and mechanical vibration. Whether the mechanical accuracy is high or low, whether the gear design is reasonable, and whether the gear assembly is appropriate, these are the main reasons for the bar to be comprehensively and multilayered energy-saving technical transformation
the countermeasures to solve the bar are:
1. Correct the gear: the axial force is harmful in the transmission, which will make the gear move back and forth in the transmission. This kind of movement will cause the ink bar on the print and wear the printing plate. Since the helix angle is determined by the main drive gear, this parameter of the plate roll gear must be the same, but the treatment of each manufacturer in eliminating the influence of axial force is different. The general practice is to greatly reduce the number of molds in the nylon oil pan parts of the gear. The chamfer at the top corner is directly connected with the motor, and with the rotation of the motor, the lead screw also rotates 45 degrees to remove the sharp edge, However, the practice of a well-known manufacturer is to grind the two sides of the gear obliquely from the tooth root to the tooth top, and the grinding height is 1/2 of the tooth height; Empty the clearance of axial force to avoid the vibration of the gear caused by the axial force generated in the operation of the gear
2. stagger the printing plate. The purpose of staggering the printing plate is to reduce the jumping of the plate roller caused by the printing plate layout. Practice has proved that it is difficult to hold the jumping caused by unreasonable layout only by pressing strips on both sides. We found that when this situation is serious, the jumping of the plate roll causes the vibration of the wrinkle roll, and then causes the abnormal wear of the scraper. At the speed of 300m/min, for an order of 50000m, after printing, we found that the scraper using Swedish blue steel was worn out with obvious wavy lines. According to the specific state, the weak links in the production of products should also be exposed through climate environment experiments, mechanical environment experiments and human normal application experiments.
3. Using soft double-sided tape as a cushion to cushion is a very practical solution. However, when adopting this method, we must consider the pinholes caused by using medium density double-sided tape or low-density double-sided tape in field printing, which needs to be compensated from the aspect of ink according to the idea of solving the pinhole problem in the previous section, so as to not only buffer the appearance of bars, but also avoid the disadvantages of pinholes