Third, the printing plate surface problems
Print bar marks are a common type of printing failure. If a resin plate is printed on a TL2640 type letterpress two-color rotary press, if the machine or the ink has a bad phenomenon, it is also easy to produce print mark defects.
1. Looseness of roller shaft head and bearing bushes. When the embossing roller or the plate roller shaft head and the bearing bush are not lubricated properly and wear and looseness occurs, fluttering or slipping is likely to occur during the printing process. Horizontal layout of the bar marks, and layout area expansion phenomenon, it should pay attention to do a good job of equipment lubrication, to prevent the failure of the problem. 2. Wear of roller gears or eccentric components When the roller gear or plate roller eccentric wear occurs, the rollers are susceptible to chattering or slippage during the imprinting process. Bars and marks, the outlets on the printed products are also easy to expand, and corresponding measures should be taken to repair the mechanical components.
3. The roller is colloidally hard or eccentric. When the ink roller is hard (such as a rubber roller), the adhesiveness is poor, and the friction is also small. In the process of printing the ink on the layout, it is prone to the situation of slippage or rubber dispensing, so that a horizontal mark is produced in the horizontal direction of the layout, so the printed layout is printed. The best use of polyurethane rubber roller or castor oil roller, its texture is relatively soft, and has a certain degree of viscosity, brushing ink more uniform, can better avoid the production of print marking phenomenon.
4. Inker roller position adjustment is not suitable. When the position of the ink roller is unsuitable for adjustment, and there is a bad contact between it and the iron roller, it is easy to cause a transverse delineation phenomenon in the process of rolling the ink. Therefore, the height of the ink roller must be adjusted to the plate. To maintain the proper contact state, the contact pressure with the stringer iron roller should also be appropriate. A 10-thread gauge can be used to insert between the ink roller and the plate surface; drawing between the ink roller and the ink roller is tested and drawn. It is appropriate to have a slight sense of resistance. 5. The ink viscosity is not suitable. When the viscosity of the ink is insufficient, and the fluidity is too large, the ink roller is likely to slip on the platen ink, causing a transverse bar mark phenomenon on the plate. Therefore, the printing ink should maintain a certain viscosity to prevent the production of a print bar mark.