Color book Overprint are not allowed to print often appear in multiple color overprint are not allowed, not allowed to overprint the front and back. There are many reasons for inaccurate overprinting, such as plate making problems, Offset malfunction, improper adjustment offset press, paper stretching deformation. Below, the author takes the Mitsubishi 3000LX off-color four-color offset printing machine as an example to analyze the reasons for the inaccurate single-sided multi-color overprinting caused by the malfunction or operation of the offset printing machine.
Weekly overprinting is not allowed
The circumferential overprinting is not allowed, that is, the circumferential crosshairs are not overprinted, and the overprinted crosshairs are in the direction of the standard line or in the direction of the tip, as shown in Figure 1. The main reasons for the inaccuracy of circumferential overprinting are as follows.
1. The position of the plate is wrong.
The improper operation of the plate loading makes the circumferential printing of each color plate inaccurate. When the deviation distance is within 2mm, it can be finely adjusted directly on the console; when the deviation distance is beyond the fine adjustment range, it can be adjusted by means of the roller. If the adjustment is still not enough, you can only reinstall it.
2. Insufficient tooth decay
The printing machine's transfer roller or impression cylinder has insufficient force, and the paper slides in the molars, causing the circumferential overprint to be inaccurate. If the pressure of the tooth is too small, the force of the tooth is insufficient, and the pressure of the tooth piece can be increased; if the friction coefficient of the tooth pad is too small, the tooth pad can be replaced.
3. The blanket or plate is loose
The looseness of the blanket or plate of a certain color unit during the printing process may also cause the circumferential overprinting to be inaccurate. The solution is to tighten the blanket or adjust the tightening screw to snap the plate.
Axial overprinting is not allowed
The axial crosshairs are not overprinted, and the overprinted crosshairs are in the direction of the standard line or in the outward direction, as shown in Figure 2. The main reasons for the inaccurate axial overprint are as follows.
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