Plate quality problems that are prone to occur in printing
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The printing plate is the carrier of printing, and the quality of the printing plate directly affects the quality of the printed product. In this article, the authors make a brief discussion about the quality of plates that are prone to print.
1, netting (clay)
Concept: Two or two groups will have different intersecting nets when they intersect at different angles or lines. The intersecting nets with large loss of aesthetics are called moiré.
Cause: The two-color or multi-color version of the screen corner or line number is wrong.
Plate making requirements: The two strong color net angles must be staggered by 30 degrees, that is, 30 degrees and 60 degrees. (In general, 37 degrees and 60 degrees can be matched.) The number of lines generally requires the same network cable. In special cases, when different numbers of lines are needed, the network cable should be staggered as much as possible.
Printing reason: ink viscosity is not suitable
Solution: When a solid version and another web version print the netting, it is generally that the ink in the field version is too thin and the ink layer is not thick enough.
2, water pattern
Concept: On the printed matter, the ink exhibits uneven, water-like printed markings.
Cause: The printing ink has poor fluidity.
Plate making improvements: change the corners of the net and increase the ditch. However, the channel can not be too large, otherwise, unevenness may occur during printing.
Printing solution: 1 increase the viscosity of the ink; 2 increase the printing speed; 3 correct the printing tension.
3, the same mesh color cast
Concept: Two or more colors of the same pattern are printed with different hue.
Cause: The two-color or multi-color version of the network cable and the net corner are exactly the same. Some dots are completely coincident during printing, and some of the dots are staggered, resulting in inconsistent visual coloring.
It is easy to produce the hue of the same mesh color, gray, purple, brown, and the two meshes are similar to the spot color superimposed.
Plate making improvement measures: When encountering a hue that is easy to deflect, try to avoid using the same mesh.
Printing solutions improve overprint accuracy
4, out point (middle water mark)
Concept: 65-80% of the web is printed with uneven spots.
Cause: Due to the fluidity of the ink itself, when the 65-80 mesh is printed, some of the dots are connected together, and the other dots are not connected together, resulting in uneven printing.
More serious hue: dark purple, brown, dark green, deep red, etc.
Plate making improvement measures: 1 change the better ink; 2 adjust the ink viscosity; 3 adjust the blade angle or pressure; 4 increase the printing speed.
5, blocking the plate (plug network)
Concept: 1 During the printing process, the ink transfer rate of the printing is continuously reduced; 2 the ink blocked in the plate is insoluble during the second printing.
Causes: 1 ink is too clean; 2 mesh pit is too small, the ink is not easy to transfer; 3 the inner wall of the net pit is not clean.
Version improvement measures: 1 high-speed cable to low-line engraving; 2 shallow mesh to increase; 3 re-chrome re-plating to ensure smooth inside the crater.
Printing solution: 1 change the dry type solvent; 2 increase the printing speed; 3 reduce the ink viscosity; 4 quickly clean the plate roll after each printing; 5 check whether the hair dryer blows the wind onto the plate roll.
6, corrosion (chrome off)
Concept: When the plate chrome surface encounters corrosive liquids such as acid or alkali, gas or unqualified solvent, it will soon react chemically, forming rust spots on the chrome surface, ie corrosion.
Precautionary measures: 1 After each printing, clean the surface of the plate with solvent (preferably Tianna water); 2 wipe the plate with a clean soft cloth, do not leave fingerprints; 3 use a brush to clean The low volatility of light motor oil is evenly applied to the surface of the plate roller. Be careful not to use waste engine oil. If the use of special anti-rust oil effect is better; 4 with a film (such as with a waste film, be sure to put the ink face out) wrap the oil-coated plate roll, then wrap the corrugated paper, stand upright or stand with a shelf It should be kept in a room that is ventilated, dry and protected from direct sunlight. 5 The warehouse should not be placed on the first floor, and should be kept away from acids, alkalis and other items.
7, drawing (knife line)
Concept: The ink that has not been scraped by the squeegee is dragged into the line-like stain on the non-image part or the shallow part of the plate roll, and is transferred to the film, which is also caused by the defect of the squeegee.
Causes: 1 the quality of the doctor blade is not good or there is a gap; 2 the ink particles are coarse or too high viscosity; 3 the blade angle or pressure is not suitable; the 4 plate roll surface is rough or not polished well; the 5 plate roll is slightly, ovality Too big or bad balance.
Solution: 1 Check whether the squeegee has a gap, use sandpaper to grind or replace; 2 filter the ink to reduce large particles in the ink; 3 sand the plate surface with sandpaper; 4 check the plate's slightly, elliptical and dynamic balance ; 5 re-polishing or chrome replating.