Detailed offset printing fault - overprint fault (3)

Four typical overprint fault examples

1. Constant speed, speed is not allowed.
Constant speed register refers to the printing of the same speed in a few colors. Different speeds do not allow different speeds to register. In general, different speeds can register, constant speed can register, and constant speed can register. Speed ​​may not register.
cause of issue:
(1) The transfer tooth and the embossing (pass) roller are not at the cut point.
(2) The transfer force of the transfer paper and the transfer (paper transfer) roller are inconsistent.
(3) The handover time is too long or too short.
(4) It is too early or too late for the paper to arrive.
(5) The paper has poor stability before it reaches the gauge.
(6) Paper stretching.

2. The side of the pull gauge is accurate and the other side is not accurate. It is simply called the operating side and the transmission side is not accurate.
cause of issue:
(1) Inconsistent brake force on both sides.
(2) Eccentric asymmetry of the transfer eccentric.
(3) The gap between the front gauge and the gap on both sides of the sheet feeder is inconsistent.
(4) Paper failures include:
a Cloth belt is inconsistent.
b The pressure of the platen roller is asymmetrical.
c Brush pressure is inconsistent.
d The pressure of the paper receiving roller is inconsistent.
(5) The front gauge and the lateral gauge are not at right angles.
(6) The difference in force between the paper-feeding teeth and the roller teeth is too great.

3. All-enveloping is not parallel on both sides. This refers to the fact that under two speed conditions, the crosshairs printed at a low speed and the crosshairs printed at a high speed have the same error, and their manifestations: one is that the high speed is not in place. The other is over-speed, very regular, with equal distances.
cause of issue:
(1) The paper arrives before the regulatory time is late.
(2) Feeding teeth closed teeth.
(3) Inconsistent elasticity of the transfer pad.
(4) The time before the paper arrives is early.
(5) Feeding teeth to close teeth as early as possible.

4. It is quasi-acceptable that the current regulations are not allowed to be printed separately without side-look. However, when combined with the side pull rule, that is, when the front gauge and the side gauge are used at the same time, overprinting is inaccurate, and the print operator calls such a malfunction to be inaccurate.
cause of issue:
(1) Bad side gauge.
(2) The gap between the side pulling plate and the iron table is too small.
(3) When holding the teeth while closing the teeth, the side pulls the gauge and raises it later.
(4) The paper arrives late.
(5) Short paper retention time.
(6) The front gauge and side gauge are not at right angles.

5. Quasi-mouthed, fault-free causes:
(1) Large print pressure.
(2) Inconsistent print lining twice.
(3) Printing plate is large.
(4) Loose cloth.
(5) Paper stretched.

6. Both sides can register, the middle set is not allowed to fault reason:
(1) Imprinting roller dents slippery.
(2) Middle tusks.
(3) The blanket is uneven.
(4) Excessive printing pressure.
(5) There is a problem with the plate.

7. The middle can register, left and right sets of failure reasons:
(1) The former rule is not on the line.
(2) There are loose teeth on both sides of the impression cylinder.
(3) The water on both sides of the plate is large.
(4) There is a problem with the plate.
(5) Rejection angle.

8. Individual sheets in printed samples are not allowed to be overprinted. That is, in more than 90% of printed samples, more than 90% of them can be registered. Only individual samples are not allowed to be overprinted. This phenomenon is mainly due to paper feeding problems.
(1) Grooves appear in the front regulation cardboard.
(2) Horizontal and vertical filaments are mixed together.

9. Misalignment overprinting is not allowed. This kind of fault is the most difficult to solve. No matter how you debug it, the rules will always bend one line.
cause of issue:
(1) The impression roller gripper shaft bends.
(2) The delivery tooth and the impression cylinder tooth are not transferred synchronously.
(3) The roller gear clearance is too large.
(4) Opening and closing teeth cam (block) wear.
(5) The machine has been used for a long time.

Source: Ke Yin Network