Wine Boxes For Gifts. Analysis of the phenomenon of loss and deficiency of lithographic printing outlets

Wine Boxes For Gifts. Analysis of the phenomenon of loss and deficiency of lithographic printing outlets

 

As one of the five elements of lithography, the printing plate has a very important impact on the quality of printed matter in printing. In the current lithographic plate making operation, although the CTP plate making method has developed rapidly, the traditional printing method is still the main form of lithographic plate making, in the printing operation, the loss of plate dot and the phenomenon of deficiency is a common fault, the following is the use of positive PS plate printing plate when this common fault causes and solutions are briefly discussed for peer reference.

 

First, the original factor

In lithography printing, the original is a copy of the object, the quality of the original will directly affect the quality of the plate, the following factors of the original will lead to the loss of the dot on the plate.

 

1, the original is mistaken for positive Yang film

In lithography, because lithography is indirect printing, and one of the characteristics of lithography printing is inverse image, it is determined that the reverse original is needed when printing lithography, but now there are quite a lot of small output institutions practitioners are not high level of business, do not know much about the printing process, often used for lithography printing of the original is output as positive film. The use of this original printing, dot deficiency and small dot loss is difficult to avoid, therefore, improve the output personnel's business level, strengthen their understanding of the printing process, is some output institutions should do.

 

2, the original density is low

In the film output process, due to under-exposure or over-development of the film, the original density value will be lower than the density value required by the printing version (the original density value is generally required to be about 3.0). If the original density value is slightly lower than the required value, the exposure time can be appropriately reduced to reduce the degree of dot loss when printing, but if the original density value is too low, only the original is replaced.

 

3, the film dot in the middle of the deficiency

In a printing, the author found that the printing plate is always not inked, using many methods to no avail, and then observed the original with a high-magnifying glass, sent to the original dot in the middle of the hollow, resulting in the printing plate dot hollow ink. This situation may be caused by the improper focus of the recording head of the phototypesetter when the film is output.

 

Second, the loss of dot and deficiency caused by excessive exposure in the process of printing

The exposure time of the printing plate is related to the depth of the printing plate. If the printing time of the PS plate is short, the printing plate is deeper and the layout is easy to get dirty. On the contrary, the exposure time is long, because the plate dot is lost, it is false, because the plate is shallow, and it is not easy to ink when printing. Therefore, the right exposure time is extremely important when printing.

 

If you replace the printing tube, adjust the lamp distance, use a different brand of light-sensitive plate or the same brand but different batches of light-sensitive plates, before the formal printing, use continuous adjustment scale, dot ladder scale or other test strips and the PS plate to be used to test the printing plate, find out the appropriate exposure time to ensure the correct transfer of the dot in the printing process.

 

In the actual printing, quite a lot of operators choose the exposure time by experience, and in the printing process often use the method of lengthening the exposure time to avoid the dirty on the page and remove the small dirty points on the page, this method has less obvious impact on the text version, but on the dot version, it will cause the loss of the dot and the phenomenon of deficiency.

 

Third, there is a gap between the original and the photosensitive version

1, insufficient vacuum

Before exposure, it is necessary to vacuum the chamber of the printing machine, so that the original and the sensitive plate are closely attached. If the vacuum is improperly set or the vacuum pump fails, the suction tube is aging and broken, and the sealing strip of the printing machine is aging and broken, there will be insufficient vacuum, and the original and the photosensitive plate can not be closely together, causing the loss of the dot and the deficiency.

 

2, there is dirt between the original and the photosensitive version

Before printing, the film should be cleaned, if the cleaning is not thorough, the film has small grains of sand and other stolen goods attached to the above, after the printing plate development, there will be dirty points, and the dirty points around the dot will be lost at the same time.

 

3, the original group

In many book and magazine printing plates, the printer, for cost reasons, often outputs small format film, and then makes a large plate by hand. In the group of large plates, the edge of the small film may appear "wavy edge" or "burr" when cutting, and these phenomena will make the gap between the original and the sensitive plate, so that the dot is lost in the process of printing.

In addition, due to the use of tape to fix the small film on the film base when assembling, if the tape is too close to the text or image area, it will also cause the loss of dots, virtual or text out of the pen break phenomenon.

 

4, even when the cover is too close to the original

In the printing plate sometimes encountered a request to use a quarto film or even an octagon film to print the folio plate, in most small printing plants, in this case, the general use of manual joint printing method to solve. Taking the folio plate with quarto film as an example, the plate needs to be exposed twice, and at each exposure, half of the sensitive plate needs to be covered. If the cover is too far away from the original position, it will cause paper waste when printing; However, if it is too close, it will cause the original in the process of pumping can not be closely together with the sensitive plate, so that the dot on the printing plate is lost and empty. Therefore, the appropriate seam size should be selected according to the paper size used in printing.

 

4. Other factors

1, photosensitive version or original crease

When printing, the two can not be closely together in the original or photosensitive version where there are creases, and the printing process will cause dot loss and deficiency. Therefore, before printing, it is very important to carefully check the original and photosensitive version.

 

2. Double exposure

Double exposure is a method that is often used to remove dirt from the pages of books and periodicals, especially when the original version is printed with a group. This method of removing dirt is to use the scattering film to make the light refract to get rid of the dirty lines and dirty points generated by the film edge, but this method will also make small dots lost, so it is not appropriate to use double exposure when the image plate is printed.

 

3. Excessive development

Excessive development will not only cause the loss of small dots, but also reduce the printability of the printing plate.

 

4. Careless revision

When retouching the plate, retouching paste or retouching liquid such as erosion to the graphic part, the loss of dot, false is inevitable. When retouching the plate, the retouching paste or the retouching liquid medicine should be washed off in time to avoid causing damage to the layout.