Analysis of Wrinkle in Offset Printing Process (II)

Second, machinery:

1. The paper that reached the front gauge was too skewed.

Cause: When the paper arrives at the front gauge, when the front is in the specified position, due to the skew, the paper is subjected to excessive force on one side, and when the stiffness of the paper is not high, the upward protrusion of the middle of the paper occurs. The mouth is not in a straight line, so that the paper that is raised in the middle will remain in the embossing area and cause wrinkles!

Possible reasons: (1) The Feda gas path is not smooth. 〈Escape airway can be>

(b) Feida adjusted it incorrectly. <correct adjustment>

(3) The pin on one side of the pendulum rod of the paper-feeding nozzle is worn badly (replacement pin)

(4) The fall time of Federer's front-side balancer is inconsistent, or the drop time is too early, and the delivery nozzle is arguing. (Get it to the right state).

2, improper adjustment of parts on the paperboard,

(a) The pressure roller is overtight or the pressure roller frame is in an inner eight character, which will flatten the original flat paper.

(2) The over-tightening of the brush wheel causes the paper to exceed the previous specified bit line before the drop of the front gauge. When the current gauge falls, it co-acts with the brush wheel to deform the paper. In general, this situation is accompanied by severe overprint or misalignment.

Solution: Correctly adjust the components on the paperboard, and the time of paper release.

3, the former rules, side rules:

(a) It is easy to print when printing three-page (banner) thin paper because the stiffness of the paper is not good and it is prone to protrude in the middle of the front gauge.

(b) The former rule, the lateral line is not vertical. When this verticality is not very serious, the paper will be crushed when the paper is positioned.

Program:

(1) Consider indenting the paper and increase the stiffness of the paper. (Figure 1)

(2) It is recommended that the adjustment range should not exceed 0.3mm when adjusting the front gauge.

(3) When the front gauge is zero line, adjust the side scale to vertical.

(3) Feeding teeth, impression cylinder teeth:

1, uneven teeth, occurred in the long-term printing small format, suddenly large format, the middle of the serious wear and tear, due to uneven at the mouth caused by imprint after printing wrinkles.

2. The transfer time between the transfer teeth and the impression cylinder teeth (or the transfer cylinder teeth) is too large or too small.

3, the distance between the paper handing pad and the paper conveying table is not suitable for the handing over (general requirement: the hem and the paper conveying table are flat or slightly lower; the swinging type is thin paper thickness *3 or thick Paper thickness +0.2mm)

The above solution: Adjust the timing and position of these teething correctly. Note: It is generally based on the impression of the impression cylinder (the four-color machine is based on the first group of imprints)! The order of adjustment is: imprinting, paper feeding, and paper conveying. (The backward adjustment is also from the imprinting start.)

4. When adjusting the side gauges, place the edge of the paper (Fig. 2) at the place where it will cause the paper corners of the cornices to reach the end of the paper and the teeth will not reach the end of the paper. If the stiffness of the paper is not good enough, or the paper is slightly blocked, Curl will not go smoothly in the next handover, resulting in wrinkling during imprinting!

Figure 2

Solution: At the same time, move the side gauge and plate to one side so that the hanging paper corner can have a bite.

5, biting force and bite paper size is not uniform: especially in the middle of the large end is small; or one side of the big side of the small; even at the edge there is no paper clenching.

Possible causes: 1 is improper adjustment of teeth. (Carefully adjust according to the steps, it can be avoided completely. Please pay attention to the following: if the site of the teeth is more than two-thirds in the width direction, the paper may slide backwards during the imprinting process and wrinkles may still occur.)


2 Closed tooth springs may have fatigue on one side or even break (eg J2108; J2205)

3 The pins of the open pendulum rod are worn.

6, teeth teeth smooth; tooth pads smooth. Lead to inefficient bite paper (Solution: Replace all the tooth pads and teeth, and avoid changing them only one at a time).

other:

In the printing, sometimes due to the ink viscosity is too large, the pressure is too large, and the rubber is aged and sticky, and other reasons cause the embossing area to the rear of the paper, the rolling force is too large, and the paper produced in the imprint when the local backward The slip produced wrinkles.

At this point, we analyzed some of the main causes of wrinkling, but in actual printing, there are often several reasons that accompany it. This requires me to accumulate experience and comprehensive analysis and judgment in my work, and analyze and handle it from various aspects. .





Source: Bison

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