§ Appendix (1) How to judge the excess of water
The ink on the printed matter is light, and even if the ink volume is increased, the ink color is not deepened in time;
The amount of ink accumulated on the ink roller increases, and the ink particles become thicker;
The sheets absorb excess moisture, and the amount of water on both sides is uneven and the paper is curled;
There is too much moisture in the surface of the ink film, and the ink added to the ink fountain is not easy to stir evenly, and the roller has a slip phenomenon;
There is sticky water at the tip of the blanket, and there are drops of water at both ends of the roller;
Before and after the printing was interrupted, there was a large gap between the darkness of the printed ink.
After the shutdown, the board will not dry.
(2) Ink volume control. Our control of the amount of ink in printing is mainly based on printed samples. This process is mainly carried out through the human eye, but experienced operators can often do very well.
First, we need to determine a reasonable color sequence based on the process characteristics of the product. Different color sequences will have different degrees of influence on print quality.
Then there is the comparison between the proofs after printing and the printed samples. There are generally two methods for this comparison. One is the visual inspection method, which compares the printed sheets and proofs immediately after printing to identify the color shades of each part (if it is The monochrome machine is not sure about the yellow color of the first printing, and it can use red or blue color filter); one is the method of hand-feeling, that is, pressing the hand on the printed image on the printed sheet immediately, if the hand is lifted, it can feel a little Sticky, that is more appropriate ink. However, these two methods require very experienced operators to use them, and they are subjective and their quality is not stable.
Modern, more advanced printing systems have introduced relatively sophisticated ink control devices. For example, HEIDELBERG's CPC system, ROLAND's CCI system, and KOMORI's PQC system all provide smart ink color control functions, replacing the artificial judgment of ink with the intelligent judgment of the computer. These systems provide possibilities for the scientificization and dataization of printed ink.
(3) Pressure control during printing
The presence of printing pressure can cause many problems such as dot gain, but since printing pressure is a prerequisite for ink transfer during printing, it is impossible to avoid it completely. Therefore, as with the above-mentioned water volume control, a general principle is also proposed for pressure control. That is, under the premise that the ink can be reasonably transferred, we advocate the use of the minimum printing pressure. This has many advantages, such as: minimizing the spread of dots under pressure; minimizing the amount of deformation of the blanket under pressure, thereby reducing the line speed difference at the surface of the drum and reducing the speed due to this Distortion caused by poor printing; reduced wear on the printing Plate , reduced the number of printing plates in the printing process, increased the stability of the printing quality; improved the service life of the blanket, and made the pressure during printing more stable……
(4) Overprint control of printed matter
Overprinting of printed matter is usually an important factor in determining the quality of the printed matter. If the problem of overprinting cannot be guaranteed, then there will be no more high quality problems.
The control over the accuracy of overprinting out of the precise adjustment of the printing equipment we mentioned in the “equipment†(provided that the printing equipment is available), there are the following factors:
1. Humidify the substrate so that its own humidity is equal to or slightly higher than the ambient humidity of the workshop.
2. Keep the workshop environment constant temperature and humidity.
3. Minimize the amount of water used during the printing process.
4. Ensure that the thickness of the printing plate liner in each color group is the same during the printing process. Due to the calendering problem of multi-color printing and the participation of water in the printing process, it is now recommended that the thickness of the printing plate liner after the color printing is slightly less than The color pad thickness is 0.03 mm.
In fact, there are many factors that can improve the precision of overprinting of printed materials, which are not listed here.
Fourth, other control aspects
In addition to the above-mentioned aspects, the operator in the printing job should also pay attention to the following issues:
(1) Carefully read the ticket, strictly follow the requirements of the ticket (such as print specifications, type of paper, and other special requirements) to avoid quality accidents caused by failure to follow the work ticket requirements.
(2) Adhere to the "three times" operation. The so-called Sanqin is in the printing process, the ink in the ink fountain, diligently look at the layout of the surface water, and the sampling control sample.
(3) Strengthen the custody of semi-finished products. The requirements for the storage of semi-finished products are that they can meet the requirements for overprinting on the under color or the backside printing, and avoid the defects such as paper deformation, imprinting, imprinting, and stain on the back due to poor storage. At the same time, in order to ensure the quality of semi-finished products, the following points must be made:
1 Piles of paper are stacked neatly. If they are stacked together, they will cause a large amount of paper edges to be exposed in the air, which will easily cause deformation due to changes in humidity. In addition, paper edges may be damaged or folded due to uneven paper edges during stacking. Phenomenon, these conditions will affect the progress of the next process, there is no benefit to the print quality.
2 Since the paper around the surface and on the surface of the pile is exposed to air, deformation of the size is easy to occur. Therefore, about 20 waste sheets should be placed on the pile surface during the stacking process to protect the printed surface. In addition, if piled up for a long time, it is necessary to put the paper stack with kraft paper or plastic film.
3 stack height of paper stack. It should be decided according to the specific circumstances, generally there are no large solid prints, piles of paper can be stacked properly higher, for large areas or high surface smoothness of the paper, should reduce the stacking height, if encountered When printing ink with a large amount of ink (especially when printing on coated paper or white card), you should consider hanging the shelves. Doing so is conducive to the drying of the ink, while avoiding the back of the dirt.
4 When encountering a very large amount of ink, the paper stack should be loosened at intervals when piled. Auxiliary drying.
The factors that can influence the printing quality in the printing process are actually not only the above-mentioned factors, but in the actual printing, there are many or such factors that may cause the printing quality to appear in one way or another. Therefore, we need to print in our work. We carefully discovered and dealt with. In addition, the standardization and standardization of management and operation should be advocated in the work, records should be made of the changes in the work, and experience should be worked out in order to facilitate data management and to achieve stable print quality.
Source: Bison
