Flexibility Features and Common Problems Analysis II

6. Long washing time, large brush pressure causes line distortion and missing dots

Due to the long washing time, the independent lines or the independent meshes may be over-inflated, easily bent or washed off. In addition, because the pressure of the brush is too large, the lines or dots will also be washed away, causing the printing plate to become obsolete. Therefore, when washing the line plate or screen plate, the plate washing time and brush pressure should be properly controlled.

7. The un-light-sensitive material is not completely dissolved, resulting in lighter shades

Insufficient flushing time failed to completely dissolve the photosensitive material without sensitization. In addition, excessive washing of the solvent can also cause this phenomenon. Therefore, wash solvents should be replaced frequently.

One of the biggest problems is the serious expansion of outlets in flexographic printing. Therefore, it is completely impossible to represent outlets under 5%, and outlets larger than 95% will be lumped into one, and the level of intermediate-tone harmonies will also be severely lost. At the same time, due to the ductility of the flexographic plates, overprinting is also very difficult. In addition, the plate-making version will often appear in the case of both the cable version and the field version, which makes the plate-making more difficult. In general, in the case of a sufficient flexo printing machine, the same color screen and field version should be divided into two productions, because the screen printing needs thinner ink layer, while the field and line version need to be thicker. The ink layer. However, under certain special circumstances, it is necessary to print the same color network lines and field images on the same plate. Under this circumstance, on the one hand, the selection of anilox rollers during printing has to be compromised. Usually, priority is given to satisfying the printing requirements of the cable screen version at the expense of the thickness of the ink layer in the field; on the other hand, it is necessary to master the difference in platemaking. Exposure time to ensure the quality of the same plate version of the Internet and field parts. The difference between the image part of the cable and the solid part mainly lies in the difference in the depth of corrosion. The part of the cable that needs to “stand” in the process of brushing the printing plate needs a strong foundation, so the corrosion depth should be shallower. This can be achieved by hiding the local method (similar to the photo exposure when blocking the exposure), with different back exposure time to get different corrosion depth. Frontal exposure time should also be similar. In addition, some manufacturers based on work experience, will be 2% of the following high-light outlets are changed to 0, because the human eye is the relative sense of color, for the very few outlets can not see. Also, replacing a color with other colors, such as replacing the black with blue, replacing blue with black in Food Packaging, or even replacing the red with red in the leaf pattern, replacing the dark with the light color of the same hue, etc. There is a certain effect. Of course, this kind of processing must require the prepress operators to have rich experience in image processing and have a deep understanding of flexographic printing, otherwise it may damage the image hierarchy and fail to achieve the expected results. According to another report, flexographic plate manufacturers have introduced a new type of flexographic plate. No matter if the printing part is a cable or a field, this plate requires only one uniform exposure time, avoiding the trouble of multiple exposures. Make the flexo plate making more convenient and the quality more stable.

Sixth, common faults in plate making

With the constant adoption of new technologies. Flexo printing has become a mature process. Although China's flexographic printing started relatively late, it has developed rapidly. However, there are also many constraints, and platemaking is one of them. Here are some common faults in flexible plate making and their solutions.

1. The blank part of the printing plate is the cause of the plugging failure and the processing method:

1 Back exposure time is too long. Care should be taken to properly control the back exposure time: 2 The main exposure is excessive. Under the premise of ensuring the reproduction of small texts and thin lines, the main exposure time should be shortened as much as possible: 3 The contact between the plate and the film is poor. The vacuum system should be ensured to work normally, and rollers should be used to drive off the air between the plate and the film.

2. Small outlets, small prints and thin lines are washed out. Causes and Solutions:

1 Back exposure time is not enough. Consider increasing the back exposure time: 2 main exposure time is not enough. Can increase the main exposure time; 3 wash plate time is too long or brush pressure is too large. Pay attention to shorten the washing time and adjust the brush pressure.

3. The reason why the bottom of the plate is not completely hardened and its treatment method:

1 Back underexposure. Increase the back exposure time; 2 flushing is not complete, there is residual unhardened resin retention. Check the brush pressure and adjust the wash time.

4. The inconsistency of the same plate wash depth causes the failure and how to deal with it:

1 Shaiban machine is too hot. Carefully inspect the ventilation and cooling system for any malfunctions; 2 The intensity of the typography lamp is uneven or the opening is not synchronized. At the same time, replace all the lamps; 3 washing brush is not parallel or the action is not balanced. Adjustable brush pressure and leveling.

5. Part of the image is blurred and the cause of the failure and its handling:

1 film is defective. Carefully check that the image on the film is clear; 2 wrongly use offset film for flexo printing. Reproduce qualified flexo film.

6. The reasons for the loss of small outlets during printing and the processing methods:

1 Insufficient main or back exposure. Can increase the main exposure or back exposure time; 2 original design beyond the flexographic reproduction capabilities. Improve manuscript design to suit flexographic technology.

7. Rupture failures and handling methods when moving and bending after field and text platemaking:

1 The main exposure and back exposure time is too long. Can reduce the main exposure and back exposure time; 2 removal of sticky time is too long. Reduce the removal time; 3 main exposure and underexposure. Check the lamp for damage or deterioration.

8. The thin lines are curved and wavy. Causes and Treatments:

1 Back underexposure. To increase the back exposure time: 2 The main exposure is insufficient. To increase the main exposure time; 3 lack of drying time. To increase the drying time: 4 wash plate water is not fresh. Replace fresh wash water; 5 wash time is too long. Adjust the wash time.

In a word, since the influence factors of flexographic printing are numerous and vary greatly, prepress production plays a fundamental role in the whole printing process. The foundation is not well laid, and the subsequent work is difficult to accomplish well. Therefore, it is required that the pre-press processing requires the staff to comprehensively consider in many aspects, and all related factors should not be neglected. It is better to sum up a set of experience in practice to serve the future work so that the prepress process can be maximized. With the printing, so that prints get the best results. (to be continued)