How to eliminate the printing bar during the offset printing process
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Although the reasons for the generation of the bars are very complicated, as long as they are carefully analyzed, some rules can be found.
a. The drive gear of the drum is seriously worn or the tooth gap is too large, which may cause the bar. The tooth surface is stained, the hard object is embedded in the tooth gap, or the root of the tooth is blocked, which may cause the bar.
Solution: Reduce or avoid accidents by properly maintaining, maintaining and eliminating foreign objects.
b. The roller bearing is worn out seriously and can cause the bar.
Solution: pad the paper in the blanket so that the mouth cushion is trapezoidal to reduce the impact of the jaws when pressed, or replace them with wear-resistant bearings.
c. If the pressure between the plate cylinder and the blanket cylinder is too large, the blanket will generate a large sliding friction under the action of the extrusion, causing the dot to be deformed to form a ink stick.
Solution: Adjust the pressure between the two rollers instead of blindly feeding the rubber pad.
d. The lining is not suitable. The lining of the printing plate and the blanket cylinder is not suitable, and the sliding friction between them drives the plate cylinder, that is, the surface driving of the drum is in conflict with the driving of the drum gear. This type of failure occurs when the pressure is small and the blanket cylinder is thicker.
The solution is to reduce the surface line speed error of the blanket cylinder and the plate cylinder, appropriately reduce the blanket cylinder liner and increase the plate cylinder liner.
e. Improper pressure on the pillow. When the pressure of the roller of the contact roller type offset printing machine is not normal, the lever is generated. The contact condition of the roller is related to the meshing condition of the gear. The pressure of the roller is not good, the gear meshing is not good, and the roller is easy to cause vibration and generate a lever.
Solution: Re-adjust the pressure of the roller according to the instructions.
f. The pressure between the inking roller and the surface of the printing plate is too large. The pressure between the inking roller and the inking roller is too large. The pressure between the water roller and the plate is too large.
Solution: The contact width of the inking roller with the surface of the printing plate is not more than 6 mm; the contact width between the inking roller and the inking roller is preferably within 5 mm. Reduce the pressure between the water roller and the printing plate.
g. Ink roller gear, medium wheel misalignment or wear. Ink roller bearing is damaged.
Solution: Replace the corresponding parts and the fault can be eliminated.