Offset printing plate abnormal phenomenon and processing (on)

As an offset plate maker, he will encounter various abnormalities from time to time. According to different situations, different methods of handling should be adopted.

The original density is not enough

Sulfuric acid paper density is not enough, especially large characters and solid blocks. Generally use a thickening agent (blackening agent) to apply (note that when the application of the thickening agent can not be too much), until after drying in the same place can be applied a second time, all dry before the print version. However, sometimes it is still not enough to apply only the density of the densifier. At this time, there are two methods of treatment.

(1) Apply ink or cover with black paper

The ink is suitable for large prints and more complex designs, covered with black paper, suitable for field bars. It is also possible to combine the two methods by first coating the edges and narrower spaces with ink, and then covering the remaining large blocks with black paper. Be careful not to use too much ink, otherwise the sulfate paper will wrinkle and affect the quality of the printing plate.

(2) Repeated copy method

With the method of repeated copying, a film master with sufficient density can be obtained. First, the negative image is copied with less exposure time and development time (generally 50% to 70% of normal time), and the silver particles that are displayed in the negative part of the negative image due to insufficient density are scraped off. The figure is copied a second time with more time (usually 120% to 150% of normal time). In this case, a sufficiently dense film is generally available. If it is still not enough, you can copy it again.

Film has fog

Film on the fog can be used to increase the exposure time or development time, increase the concentration of the developer solution to deal with, but must ensure the quality of the text. If it is not guaranteed that the image quality or fog is too heavy, the film has to be re-launched.

Uneven text stroke thickness

This situation is common in sulfated paper because of the failure of the laser printer or the poor quality of the sulfate paper itself. It is also possible to apply a densifier to improve the gap between the thickest strokes and the finest strokes, but it does not completely eliminate the uneven thickness. At this time, the printer should be repaired or the sulfate paper should be reissued after the paper is replaced.

Version of the heart is geometrically deformed or varies in size

Geometric distortions are often caused by improper printer adjustments, but they also occur by chance. Deformation often occurs on sulfuric acid paper, mostly parallelogram deformation, that is, the rows and columns of the printing plate are not perpendicular. When the deformation or size is not equal, the sulfuric acid paper can only be recycled. If the customer's consent is not serious, sulfuric acid paper may not be regenerated. In this case, it is necessary to use the side of the incision on the side of the printing plate as the base. The imposition is based on the page number. Because the printing center is not accurate on the basis of the side of the printing plate on the side of the cut, but if it is based on behavioral criteria, overprinting will be very serious, and when the side of the cut side of the plate is used as the reference, the spine Side misalignment is not easy to find.

Sulfuric acid paper itself deformed

Sulfuric acid paper deformation is very common, the performance of unspelled sulfuric acid paper appears flounces, has been spelled longer, affecting inhalation. If the length is not serious, the degree of vacuum of the printing machine can be properly adjusted, and the level of vacuum can still be increased. However, if the length is very serious and the suction is affected, the hair dryer can be blown appropriately and the sulfate paper can shrink. If it is not, it will not work. Therefore, it will have to be re-exported and imposed.

Graphic content needs to be changed

Making changes to the original is more common, sometimes because of errors and corrections; sometimes because of changes in customer requirements that need to be corrected.

Not all changes to the original edition require the re-sulphuric acid paper or film to be re-exited. In the following cases, there is no need to re-enter.

1 Make changes to the non-mesh adjustment graphic;

2 Manual correction is easier and less time-consuming;

3 The hidden dangers left after the manual correction, such as the film edge marks, the edges of the transparent glue, etc., can be easily eliminated;

4 Manual correction does not affect the quality.

The sulfuric acid paper or film used for correction should be as far away from the existing graphics as possible, otherwise the graphic or text will be reduced or made false.

(to be continued)