Analysis of the rules of offset printing machine (1)

1.3 Rules section

The role of the rules part to the positioning of the paper, so that each paper can enter the printing unit in the same position, so its accuracy directly determines the size of the overprint error of the print, so the installation and adjustment of the rules part is very important .

1. The working principle of the rules section. How is the paper positioned in the regular part? In actual work, the paper first goes to the front gauge, and after the front gauge is in a static state, it is pulled to the side gauge edge. The front gauge positions the paper in the forward direction and the side gauges position the paper in the lateral direction. The general rules of the general machine are at least two or more, and most machines have more than four, but only two are used for positioning. Why do you use only two? This is because two points determine a straight line, which is less or less. More interference will occur.

After the front gauge of the side scale was finished, it pulled the paper to the side of the rules. This actually adds another anchor point to the paper. In addition, the paper is positioned on three points in front of the front gauge, so the entire plane position of the paper is determined. From the foregoing analysis, it can be seen that the positioning principle of the regulatory part actually uses the geometry principle of two points, one line and three points.

A simple analysis of the positioning of the paper above has led to a more in-depth analysis. It shows that paper is not only positioned in a plane but also positioned in space. This means that the entire paper is always placed in a certain space. The paper's spatial orientation has high requirements on the working status of the regulatory part. This is one of the keys to adjusting the front gauge and the side gauge.

2. The role of the former rules. The former rule is to position the paper longitudinally. This is one of the main functions of the former rule. In addition, the former regulation has many other effects. Here's a summary and summary of these effects.

(1) Longitudinal positioning of the paper The longitudinal positioning of the paper directly determines the overlay accuracy in this direction. If you do not position or misalign the paper in this direction, it will cause a series of printing failures. Such as pleating, ghosting and so on.
(2) Change the size of the mouthwash. During the printing process, sometimes the size of the mouthwash needs to be changed. There are two ways to solve this problem: one is to use a roller; the other is to adjust the front and rear position of the front gauge. The amount of change in the current regulations is relatively small, and it is still more convenient to move ahead.
(3) Remedying the errors of plate loading and printing plates Plate printing and printing plates are theoretically difficult to ensure that all images are in the standard position. Generally, the calcium in the situation line needs to reach a certain position through the slight adjustment of the front gauge. This is also one of the important roles of the former regulations.
(4) Misfeeding error During the feeding process, the paper enters a semi-constrained state from the free state. It can be said that each time the front gauges are not in the same position, they are brought to a certain position by the former rules.
(5) Creating a conditional side specification position for a side position is performed on the basis of the preceding specification position. Therefore, the former position is a reference for the side pull. This can be seen from the design of the press. Under normal circumstances, the formerly specified position is accurate, and the machine will not stop if the side specification is inaccurate. However, if the position is not defined, the machine will automatically stop. This is because the side specification is not accurate, but as long as the former specification is accurate, the printed product can sometimes be used.
(6) Adjustable for various types and sizes of paper The printed paper is changed according to the user's requirements. It cannot always be the same. Therefore, the front gauge must be able to make corresponding according to different types and sizes of paper. Adjustment to ensure accurate positioning of the paper.

3. The classification and working principle of the former regulations.

(1) The classification of the former regulation The former regulation is generally divided into two types, the upper one and the lower one.

Compared with the front rule of the hem type, the upper swing-type front rule is very convenient for adjustment and installation; the second is that the front-end scalloped paper can be eliminated without any additional mechanism; the hem type front Compared with the front rule of the pendulum type, the gauge can return to the paper feeding plate when the paper has not completely left the paper feeding plate, so that the positioning time of the front gauge is increased and the positioning accuracy is more easily ensured. With the same positioning time, the speed of the machine can be increased. Therefore, the upper swing-type front gauge is suitable for low-speed large-format or high-speed small-format, and the hem-type front gauge is suitable for high-speed large-format, which is a clear feature of the contemporary offset press.

The disadvantages of the hem of the hem are the complex installations and the need to add special mechanisms to eliminate the flounces.

(2) The working principle of the front gauge The front swing mechanism does not need to additionally eliminate the mechanism of the lotus leaf. It only performs swinging. In general, its swinging motion is achieved through a cam-driven linkage mechanism.

The following requirements are imposed on the former regulatory movement:

1 When positioning the paper, stabilize it on the paperboard in advance.
2 When the paper-feeding paper leaves the front plate, the front gauge should be set down to let the paper advance.
3 When the front gauge swings backward, it should not interfere with the previous piece of paper. The front gauge must achieve these points, and the parts must be flexible in motion and accurate in time and displacement. At the same time, each part should have the smallest string and jump. The level of the former regulation and the adjustment agencies before and after are generally more complicated. The domestic equipment uses a linkage mechanism. Heidelberg uses a three-point suspension mechanism.

The regulation of the former rules must take into account the changes in the paper and the impact on the side rules. This point will be analyzed in detail when it comes to side views.

4. The role of lateral regulation. The lateral orientation of the paper is one of the main functions of the side gauge. Like the front gauge, the side gauge has many other effects.

(1) The lateral positioning of the paper The lateral positioning of the paper is an important measure for ensuring the overprint accuracy of the paper in the lateral direction. The former position is accurate, and if the side specification is not accurate, it will cause great difficulties for the subsequent overprinting or cutting of the printed sheets.

(2) Remedy the error of plate loading and printing plates When the current rule is adjusted according to the errors of plate loading and printing plates, the angle of the side plate should also be adjusted theoretically so that the front plate and side plate are always kept at right angles to the paper. Positioning. Therefore, this institution is also set up on the side plan.

(Figure 1.12)

(3) Make up for the lateral pull amount of paper feeding or paper cutting error side rule is 0-12mm, how much suitable for this in the end? If choose 12mm, it is the maximum pull amount. Select this amount of paper as long as the pull gauge can reach the range of paper can be positioned. However, due to paper feeding and cutting errors, some papers may be outside 12mm, and such papers cannot be positioned. If you choose 0mm, that is, do not pull the paper, so obviously with no sideline the same. The paper becomes two-point positioning and does not meet the requirements for planar positioning. The general choice of paper pull is 5-8mm. Choosing the pull amount of 5-8mm does not mean that the pull amount of paper is 5-8mm. The amount of paper pulled is only an average number, and the vast majority of paper is within this range. If there are errors due to paper feeding, some papers are not within this range. Dora more than 8mm, pull less than 5mm. Therefore, the amount of paper pulled actually changes between 0-12mm.

(4) The adjustment of various papers and webs can be adjusted due to changes in the web and thickness of the paper. The lateral moment can be adjusted accordingly to ensure accurate lateral positioning.