The lithographic printing outlets are lost and made empty (1)

As a printing plate that is one of the five elements of lithographic printing, the influence on the quality of the print during printing is very important. In the current lithographic platemaking operations, although the CTP platemaking method has developed rapidly, the traditional printing plate printing method is still the main form of lithographic printing. In printing operations, the loss of printing plate outlets is a common fault. The reasons and solutions for this common failure when using positive-printing PS plates for printing plates are briefly discussed for reference by peers.
First, the original factor

In the lithographic printing, the original is a copying object, and the quality of the original will directly affect the quality of the printing plate. The following factors of the original plate will cause the dots on the plate to be lost and become imaginary.

1, the original mistaken for Zhengyang film

In lithography, since lithographic printing is indirect printing and one of the characteristics of lithographic printing is reverse image, it is determined that reverse printing is required when lithographic printing is used. However, there are quite a number of small output agencies. The level of business is not high, and the printing process is not well understood. The original used for lithography is often output as forward film. It is difficult to avoid the loss of dots and small dots when using this original printing. Therefore, improving the level of output personnel and strengthening their understanding of the printing process is something that output agencies should do.

2, the original density is low

In the process of film output, due to underexposure or overdevelopment of the film, the original density value will be lower than the density required by the printing version (general requirement of the original density value is about 3.0). If the original density value is slightly lower than the required value, the dot loss can be reduced by appropriately lowering the exposure time when printing, but if the original density value is too low, only the original plate is replaced.

3, film outlets in the middle of virtual

In one printing, the author found that the printing plate was not inked, and it was useless in many ways. Later, the original plate was observed with a high magnification magnifying glass and sent to the middle of the dot on the original plate. As a result, when the printing plate was printed, the printing plate became empty. Ink. This may be caused by the improperly focused recording head of the imagesetter during film output.

2. Loss of network points caused by overexposure in the printing process

The printing exposure time relates to the depth of the printing plate. The printing time of the positive printing version of the PS plate is short, the printing plate is dark, and the layout is easy to get dirty. On the contrary, the exposure time is long, because the printing plate outlet is lost, and the printing plate is missing because the printing plate is shallow. It is not easy to get inked when printing. Therefore, the proper exposure time for printing is extremely important.

If you change the lampshade and adjust the lamp distance, use different brands of photographic plates or photographic plates of the same brand but with different batches. Before the official printing, apply continuous adjustment ruler, dot ladder or other test strips. Want to use the PS version of the trial printing, find the right exposure time, to ensure the correct transfer of dots in the printing process.

In the actual printing, a considerable number of operators choose the exposure time based on experience, and in the printing process often uses a longer exposure time to avoid dirt on the layout, remove small spots on the layout, this method of text The influence of the edition is not obvious, but for the dot edition, it will cause the loss of outlets and the emergence of virtual phenomenon.