Offset Part Printing Faults (1)

At present, in some small cities and township printing enterprises, the application of offset printing machines is very common, but most of them are monochromatic old models, namely PS2101 offset printing press. Due to the low level of automation, it is entirely up to the operator to master the entire printing process. In the offset printing process, various kinds of printing often occur, so that those who lack experience are even baffled. I talk about some experience for peer reference.
First, the blanket is not installed caused by printing failure Offset machine blanket is a very detailed work, not well installed can cause a lot of failure, such as the printed end of the product is a real one end, ink dark before and after, Within 30cm of the mouth, the strokes became thicker, and the product appeared to be lumpy and dark.
The one-side and one-side end of the printed product is often considered to be insufficient pressure, but it is not. This was the case after the new blanket was installed on the machine. The main reason was that the blanket was not installed properly. Although the rubber upper and lower cleats are arranged in parallel, but the four corners are not at right angles, they become parallelograms; or the distance between the front and back cleats of the rubber is not the same, and it becomes a quadrilateral that is neither parallel nor long and not equal; Equipment. In this way, there is an elastic inconsistency at both ends of the eraser on the same printed surface. The elasticity of the elastic end of the rubber is larger, the elasticity of the tight end is relatively small, and the amount of compression at both ends of the eraser is also not the same, so the printed product has the feeling of a virtual end.
After the machine shuts down, ink suddenly appears in the middle of the print, or appears dark and fades. The strokes within 30 cm of the mouth become thicker and ghosting. It may be that the rubber gargle is loose, the screw is not tightened or the yoke tip is worn, or the shaft teeth are not filled with ink. If this is the case with the new eraser, it may also be due to the fact that the rubber drag is too tight.
The new eraser on the machine, product outlets, strokes of different sizes, block thickness uneven, virtual reality, it may be caused by uneven thickness. Broken pens, broken dots, missing dots, or missing paper are of poor quality, such as paper blocks, grass stems, sand, etc. If it is a problem with the plate, let's say something else.
Exclusion method: When installing a new eraser, first measure the length, angle, and radial direction, and cut it into a regular square. Drilling is an important part of the process. Mark the line and make it correct. The four corners must be perpendicular to each other. If the eyes are closed, the splint will not be properly installed. If the rubber is not installed well, in order to save time, use adjustment pressure to solve, it will lead to a variety of contradictions, such as the center distance between the two ends of the drum, the pressure of the rubber deformation greatly shortens the rubber life, to accelerate the sleeve wear.
Eraser and rubber should be paid attention to whether the upper and lower braces are intact and the shaft teeth should be cleaned. Every time the rubber is used, it must be tightened. Use your finger to stretch it.
When replacing the rubber, it should be replaced with cloth and liner paper at the same time. The liner paper should be smooth and smooth. Also check if the pressure of the three rollers is reasonable. Adjust the pressure, press the rubber for one minute, then draw the map with semi-pressure and compaction plots, and fill the low spots with 28~35g/m2 paper to get the ideal flat printing surface. The cut cannot be resolved by increasing the pressure.
Second, the pressure caused by irrational printing press cylinder pressure is too large, it will cause pressure ram rubber, wool cloth slippage, serious. The rubber patch is a piece of this one; the network is enlarged, the level of the original is lost at the level of high and low levels; the peeling angle is large, and the india plot is easy to peel and other faults. When the excess pressure is less than zero, the embossing roller sticks to the ink. Paper wrinkles tend to wrinkle.
Impression cylinder pressure is too small, the product ink is not printed. Loss of outlets, broken pens and broken paintings, the entire printing surface is empty.
Excessive pressure on the plate cylinder and the blanket cylinder will cause the printing plate and the text to gradually wear out, and the printing plate will emit light. In severe cases, only one printing plate will be printed with only a few thousand impressions. There will also be fuzzing of the product. When the ink is large, the dots will be enlarged and the lines will be thicker.
Plate cylinder and blanket cylinder pressure is too small......
Exclusion method: The pressure between the impression cylinder and the blanket cylinder is too large. Firstly, it can be seen from the eraser that the eraser is white and the surface of the eraser is dark under normal conditions. This is because the ink on the eraser is completely absorbed by the paper under heavy pressure, and the paper is white because it is left with a lot of paper hair. When printing thin paper, it can be seen from the reverse side of the product that the shadow is more serious.
The pressure of the blanket cylinder and the impression cylinder is too small, and the surface of the rubber is dark. This is because the ink is not completely transferred, and the rubber tug even has a water film.
How much pressure is it between the blanket cylinder and the plate cylinder and the impression cylinder? The author believes that the compression of neutral blanket rubber cylinder and plate cylinder is 0.08mm, and the compression pressure of blanket cylinder and impression cylinder is 0.08mm plus a printing paper is the ideal pressure. If white paper is printed, it is best to increase the center distance between the impression cylinder and the blanket cylinder. Some operators use the reduced rubber pad to add printing plate whitening method. This changes the ink transfer coefficient of the ink roller to the printing plate, and also increases the friction force of the ink roller on the printing plate. In short, it has many advantages and disadvantages. (To be continued)