Analysis of the rules of offset printing machine (2)

5. The type and working principle of side regulations.

(1) Classification of side regulations The side fairies are generally divided into two types, namely, push rules and pull rules. The push rule pushes the paper in the opposite lateral position, pulling the paper to pull the paper in the lateral position of the rule.

Push rules can also be found on earlier machines, and most of the presses now use pull gauges. This is because the flexibility of the paper exists, and it is difficult to maintain the positioning accuracy with the ejector gauge. The next main thing to talk about is the side pull gauge.

The side pull gauge has fan-shaped plate type, roller type, magnetic stripe type and so on. Fan-type pull gauges were used on earlier domestic machines and are now largely eliminated. At present, almost all Beiren equipment use roller type. Heidelberg machines use magnetic stripe pull gauges. The advantage of the roller type pull gauge is that the reciprocating motion is changed into rotational motion, so the inertial impact is very small. The disadvantage is that the contact surface with the paper is small, and when the vibration is large, overprinting is not easy.

The magnetic stripe pull gauge is characterized by a large contact area with the paper and a relatively small influence on the positioning accuracy of the front gauge. However, this structure is relatively complicated and installation accuracy is also very high. There are the following requirements for the movement of lateral regulations:

1 Before the pull is finished, the paper can be pulled. 2 When taking paper, the side gauge must leave the surface of the paper. 3 It must be stable during the pull of the paper (the side gauge always keeps in touch with the paper).

(2) The principle of side-pull drawing The side-drawing paper is based on friction. The principle of formation of friction is similar to the principle of friction of paper on the paperboard. Therefore, to make the paper reliable, you must create friction. Force formation conditions. Paper stress analysis is as follows:

(Figure 1.13)

F1 is the friction force generated by the driving part, f2 is the friction force generated by the follower (usually refers to the rollers), and f3 is the friction generated by other components on the surface of the paper. According to the movement requirements, f1=f2+f3.

Both f1 and f2 are proportional to the pressure of the lateral spring. F3 is directly proportional to the force of other parts on the paper. F3 force includes: friction between paper and paper, resistance of side platen, etc. The relationship between the three forces f1, f2, and f3 directly affects the positioning accuracy.

According to the role of the side rules, it can be seen that the side rules should have the following functions:

1 According to the change of paper format, the horizontal direction can be relatively moved;
2 According to the change of paper thickness, relative adjustment can be made in the height direction;
3 According to the needs of the drive, the pressure of the roller on the paper should be able to adjust;
4 According to the needs of the position coordination, the angle between the side fence and the front gauge can be adjusted (making it in a right angle state);
5 According to the timing relationship, the starting and ending times of the side pulls should be adjustable; 6 the choice of working and non-working states.

6. The former stipulates the influence of the contralateral regulatory position. First, the former regulation is the benchmark of the lateral regulation position. Only the former regulation position is accurate and the lateral regulation position is meaningful. Secondly, if the front gauge is too low, it will produce a large friction on the surface of the paper, thereby destroying the conditions of the side-slide friction drive; if the front gauge is too high, the positioning accuracy is very low, and the side-specified position cannot The paper is effectively corrected. Therefore, the front gauge cannot be too high or too low. Generally, the height of the front gauge is 0.20 mm thick, which can basically maintain the positioning accuracy, and at the same time, the frictional force that hinders the lateral movement of the paper is also relatively small.

In order to be accurate in the positioning of the side guides, all the friction must be overcome, which is not necessary when adjusting the machine. The height of the sidebar baffle is 0.20mm thicker than the paper thickness, which can ensure that the resistance of the paper into the side gauge is relatively small. The other is to adjust the tension of the pull wheel to change the conditions of the friction drive. Therefore, we must pay attention to the impact of the provisions of the provisions of the contralateral side, with the pressure of the former rule should pay attention to this point.

7. Hand paper teeth. Paper handing is an extremely important part of getting the paper from a semi-free state to a controlled state. The reliability of this state directly affects the accuracy of overprinting, so the requirements for all parties, from design, processing, installation, etc., to face-feeding are very high. Generally, the following requirements are met for the paper handler teeth:

(1) Self-trajectory

1 Absolutely stationary with respect to the paperboard. This is a key step in paper handover. Only absolute motion can guarantee the smoothness of the transfer and do not destroy the positioning accuracy of the paper.
2 uniform acceleration movement of paper from the paper to the impression roller or transfer roller. This requirement ensures a smooth transfer of paper and minimal inertial impact. This is the key to designing a delivery paper cam. In fact, designing the delivery paper cam does not necessarily have to wait for acceleration or equal deceleration. The key is to require smooth movement and minimal inertial impact.
3 The paper is transferred to the subsequent cylinder relatively stationary. Only when it is relatively stationary, the paper can be transferred. If it slides relatively during the transfer process, the accuracy of the transfer is destroyed.
4 Evenly decelerate from the drum to the paper feed. This requirement minimizes the settling time required for the paper to return to the paper feed, allowing it to enter an absolute standstill as quickly as possible. This is also a key part of designing the delivery paper cam.

(2) Relative movement requirements

1 After the front gauge and the side gauge are finished, the paper feed teeth can be taken to the paper feed board.
2 When the paper-feeding teeth leave the paperboard, the front gauge should leave the paperboard in advance.
3 When the pad of the paper feed tooth and the pad of the back transfer roller are parallel, the paper can be transferred.
4 When a paper feed failure occurs, the paper feed tooth is not on the paper feed board.

(3) trajectory requirements

1 Smooth trajectory, minimal inertial impact.
2 In the trajectory, it cannot interfere with any other components.

(4) The requirement of its own precision

1 All tooth pads are flush and the coefficient of friction is evenly distributed.
2 All tooth pressures are consistent and the contact is even.
3 All tooth chips have the same movement.
4 open and close tooth mechanism is flexible and reliable.
5 The paper feed shaft has minimal movement and runout.

8. Various types of paper feed and how it works. Paper handing teeth are generally divided into four categories: swing-up, hem-type, roller-type, and over-type.

(1) The swing-up type swing-up type is divided into four categories: the centering swing-up type, the tilt-type swing type, and the eccentric swing-type swing type.

1 centering swing type: This kind of paper-feeding tooth has inconsistent back and forth motion trajectory, that is, the position of the paper-feeding tooth is relatively high when the rollers return to the feeding board, and the height is changed with the amount of eccentricity, but this kind of paper-handling structure It is complicated, and the inertial impact increases with the increase of the eccentricity, so the eccentricity cannot be particularly large. Sometimes it is necessary to add a special anti-fouling mechanism 2 eccentric swing-type swing: This kind of paper-feeding teeth and eccentric swing above the similar, inertial impact is relatively small.

(2) Analysis of the sloping principle of the upper swing mechanism When the transfer teeth pass the paper to the following roller, the paper will be oriented along the tangential direction of the roller as shown in Figure 1.14.

(Figure 1.14)

In this way, the paper-handling tooth easily swings against the tail of the paper when swinging back, especially thick paper or high speed, which is even more serious. Therefore, if printing thick paper or high speed, there must be a special anti-fouling mechanism. The anti-fouling mechanism mainly bends the tail of the paper, which prevents the paper feed teeth from colliding with the paper.

(3) Pendulum-type hem type is currently seen, namely, centering swing type. Without eccentric swinging, the main reason is probably that the installation space is too small. The main advantage of the pendulum type and the pendulum type is that the paper feed tooth can be returned to the paper feed plate when the paper has not completely left the paper feed plate, so that the transfer time can be prolonged and the stability of the transfer can be improved. Increase the speed of the machine.

(4) analysis of the scumming mechanism of the pendulum mechanism. When the transfer teeth pass the paper to the following rollers, the paper will be oriented along the tangential direction of the rollers. As shown in Figure 3.14.

In this way, the paper-handling tooth easily faces the surface of the paper when it swings back, and the tail of the paper starts to vibrate when the paper leaves the paper-feeding sheet. The amplitude of the previous week or two was particularly large, so the possibility of filth was very high. This phenomenon is even more pronounced when printing on high speed or thick paper. Therefore, special anti-fouling organizations must be added. The current method is to add a freely rotating roller on the tooth gasket so that when the tail of the paper collides with it, there is no relative sliding between the paper and the paper, so as to avoid dirt. Even so, if the paper is extremely thick, the speed of the machine is very high, and the impact of the tail of the paper is very large, and it is still easy to destroy the graphic on the back of the print.

(5) The rotary drum type rotary drum type is generally divided into two types: one is an intermittent type, and the other is a constant speed rotary type. The former is mainly used on low-speed machines and is now being phased out. The most commonly used rotary speed type is the Heidelberg press. One of the greatest advantages of the uniform rotary type is that the possibility of picking up is completely eliminated, and it is smaller than that of the eccentric swing type. However, this paper-feeding tooth can only return to the paper-feeding board after the paper completely leaves the paper-feeding board. Compared with the hem type, there is a problem that the paper-drawing time is insufficient, and another disadvantage is that the structure of the paper-feeding tooth is compared. complex. Therefore, in the high-speed printing press, the delivery tooth is likely to be eliminated.

(6) The position of the transcendent transcendental extension paper is performed on the roller, so the speed of the machine can be higher, but due to the accuracy of the positioning of this mechanism, especially for large-format, positioning accuracy is lower, so generally it is This mechanism is used on small offset presses.

The transcendental type is generally divided into two types, namely pneumatic type and friction type. Pneumatic pressure difference to the paper passed to the roller, rubbing friction wheel to pass the paper to the roller.