Positioning device of the hottest sheet fed offset

2022-08-22
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The main adjustment of the positioning device of the sheet fed offset press

the second paper transfer device

the paper transfer device directly affects the paper transfer accuracy and overprint accuracy. Therefore, the adjustment of the paper transfer device is a very important and detailed work. The following takes the eccentric up swing paper transfer device as an example to introduce several adjustment methods

1. Adjustment of the joint position of the paper delivery teeth and the drum teeth and the front gauge

the joint position refers to the relative position of the two joint parts when handing over the paper. Taking one part as the benchmark, adjust the position of the other part to match the benchmark position. The adjustment of the joint positions at each part is in order

the paper delivery teeth and the front gauge and the roller teeth take over the paper twice. At the position of the two paper deliveries, the paper delivery teeth can be determined at the front gauge after adjusting the delivery position of the paper delivery teeth based on the impression roller teeth. Then, based on this position, adjust the working position of relevant parts at the front gauge

figure the interface between the paper feeding tooth and the drum teeth

the interface position between the paper feeding tooth and the front gauge: it is determined by the positioning screw 10. When adjusting, slowly rotate the machine to swing the paper feeding tooth to the front gauge, and the positioning screw presses against the stop 14 on the paper feeding tooth shaft. At this time, there is a gap of 0.03 ~ 0.05mm between the low point of the cam and the roller. If the gap is too large or too small, turn the positioning screw to adjust, of course, It is required that the jacking time and force of the set screws on both sides and the stop should be consistent. Then adjust the positioning plate of the front gauge so that the positioning plate and the paper feeding tooth are in a parallel line, and the paper feeding tooth picks up the paper in the range of 3 ~ 5mm (see Figure)

2. adjustment of the height of the paper delivery tooth pad

the adjustment of the height of the paper delivery tooth pad is based on the height of the tooth pad of the embossing cylinder. The ideal state is that the gap between the paper delivery tooth pad and the tooth pad of the embossing cylinder is a piece of printing paper thickness at the "0" position. However, because the paper is soft, the paper edge cannot be flat, and various factors such as adjustment, motion error, paper thickness change, etc., this state is difficult to achieve, so in general, the spacing between two tooth pads is two printing paper thickness, or one printing paper thickness plus 0.2mm is more appropriate

the specific adjustment method is: first, use a steel sheet of corresponding thickness, place it flat on the working surface of the roller tooth pad, loosen the fixing screw, make the paper delivery tooth pad lean against the steel sheet gently, and then tighten the fixing screw, so as to adjust all the tooth pads in parallel rolling one by one. The current challenge is how to control the surface chemical properties of these two-dimensional sheets on a straight line of the cylinder plane (it can also be adjusted as a whole)

the paper delivery tooth receives paper at the front gauge. When it is in the lowest position, the gap between the tooth pad surface and the paper feeding iron table should be determined according to the thickness of the paper. When printing thin paper, the gap is three times the thickness of the printed paper; When printing thick paper, it is appropriate to add 0.2mm to the thickness of the printing paper. When adjusting, take the height of the tooth pad as the benchmark, change the height of the paper feeding iron table through the fixing screw on the back support plate of the paper feeding iron table, so that the gap between the tooth pad and the paper feeding iron table meets the requirements, and then lock the fixing screw again

3. Adjustment of the paper holding force of the paper delivery teeth

the paper holding force is the pressure between the tooth piece and the tooth pad. Whether it is the paper delivery teeth or the embossing cylinder teeth, it needs to be adjusted in the printing process. This is because:

(1) the standard introduced by the spring is inaccurate due to long-term use. The spring force of the three-dimensional coordinate control method is reduced, which reduces the holding force

(2) the tooth pad is worn after long-term use, resulting in the reduction or inconsistency of the paper holding force of the paper holding teeth

(3) paper powder is often stuck on the paper teeth during printing, and foreign matters such as ink are easy to reduce the gripping force of the paper teeth and cause various faults

(4) the opening and closing time of each paper gripper is inconsistent, which is easy to cause tooth pad wear and affect the paper gripper force. The adjustment of the gripper force of the paper delivery teeth must be carried out on the basis of the accurate adjustment of the height of the paper delivery tooth pad. Otherwise, the gripper force will be affected due to the change of the height of the tooth pad. The specific steps and methods for adjusting the gripper force of the gripper are as follows:

a rotate the machine to the position where the gripper holds the paper on the edge of the paper feeding table, and control the cam and roller of the gripper to be out of contact. That is, pass the paper and hold its teeth into the closed tooth area

b insert 0.25 ~ 0 between the toothing shaft positioning block and the positioning screw (back hill). 3mm thick paper

c loosen the fastening screws of all grippers so that all grippers are not closed

d test the gripping force and adjust the gripping force in the order shown in the figure, then tighten the fastening screw 3 and place 0 between the tooth piece and the tooth pad. 1mm thick kraft paper strip is used to test the paper gripping force

e remove the paper between the positioning block and the positioning screw (backer). At this time, the holding force tension spring makes the positioning block and the positioning screw close, and all the small support springs of the holding teeth increase the equal compression, that is, the equal holding force

f adjustable screw during fine adjustment 7

figure J2108 machine paper transfer tooth structure and adjustment sequence

[related link]

there are generally two methods to test the paper holding force. One is the overall test, which is to let the paper holding tooth hold the whole paper, which is judged according to the hand feeling. The other is the individual test, which is to let the paper holding tooth hold the kraft paper strip, which is judged according to the hand feeling. Sometimes when adjusting the drum to hold the paper tooth, you can stick some butter on the tooth pad, Stick the paper strip on each tooth pad, and then close the paper teeth to test their paper holding force

[expert tips]

the adjustment of tooth holding force must prevent the occurrence of "dead teeth" (the tooth piece and the tooth seat become a whole) whenever we sit inside. When adjusting the small support spring, the screw and the tooth piece are against each other, and the holding force of the tooth piece cannot be increased. Therefore, the small support spring is compacted by the screw, so that there is no room for loosening between the tooth piece and the seat. When the general spring increases the pressure, the holding tooth will accept all the pressure of the general spring

4. Adjustment of the gripper force of the paper transfer drum

in many imported offset printing machines, the gripper force of the paper transfer drum needs to be adjusted as follows:

the distance between the teeth of the paper transfer drum and the tooth pad (Figure/①) needs to be adjusted according to different printing materials

figure adjustment of gripper force of paper delivery drum

⑴ Turn on the paper feeding safety switch

Zhai Guangjing introduction ⑵ Jog the machine forward until the locking screw can be adjusted (Fig./②)

⑶ open the shield in front of the paper transfer drum

⑷ loosen all locking screws (Fig./②)

(5) continue to jog the machine until the ruler is exposed (Fig./③)

⑥ use a socket wrench to rotate the ruler (Fig./③) to the marking line (Fig./④). Each grid on the ruler represents the thickness of 0.1mm paper

 tip: in order to prevent the pattern gap on the ruler, it is best to rotate the ruler clockwise to set

⑴. After the correction, continue to jog the machine until it returns to the position of adjusting the locking screw

⑵. Tighten the locking screw (Fig./②)

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