Knife line
Knife line is a relatively common failure, mostly in the non-graphic part, is by the scraper failed to scrape the ink on the surface of the plate blank ink due to clean. Knife line is generally divided into regular fixed knife line and irregular intermittent knife line.
Fixed knife line appears in the same position of the print, mainly because the surface finish of the printing plate is not good, the process of electro-engraving the edge of the mesh cavity burr, in the grinding failed to polish the burr clean, resulting in the printing of the layout of the burr parts of the ink is not easy to scrape clean, resulting in the formation of a fixed knife line. With 1200 purposes of fine sandpaper dipped in solvent gently sanding plate, so that the surface of the printing plate is smooth and burr-free can be solved.
Intermittent knife line in the position of the print is not fixed, from time to time, sometimes more or less, with the scraper string movement along the layout of the lateral back and forth, no regularity. The main reason for the emergence of the ink mixed with debris, ink pigment grinding is not sufficient, coarse particles and insoluble in connecting materials and solvents, printing stays in the scraper knife mouth, affecting the scraper knife scraping effect, resulting in scraping the ink is not clean, the formation of knife line. In addition, the doctor blade damaged can not scrape the excess ink clean will also cause the knife line. The solution is to replace the damaged scraper knife, with 2000 ~ 3000 mesh filter ink, the impurities in the ink filtered out, and in the ink circuit with a filter, double filtering can ensure that the ink is clean and free of debris.
Heavy shadow
Re-imaging refers to the appearance of light lines next to the printed lines or printing dots next to the side of the shadow, the side of the shadow is lighter than the main lines or the main dots. Heavy shadow emphasizes the word “heavy”, that is, in a dot or image repeated on a dark and light or the same color of the two shadows. Heavy shadow will reduce the sharpness of the edges of the print, affecting the color reproduction of the print image, so that the entire print color blur, level distortion, clarity decreased significantly. Re-imaging is mainly caused by the pressure of the pressure roller is too large, scraping knife pressure and angle is not adjusted. If the print circumferential and axial ghosting, that is caused by the pressure roller pressure will be too large ink extrusion, at this time we should reduce the pressure roller pressure until the ghosting disappears. If only circumferential ghosting, that is too small by the scraper pressure, poor contact with the printing plate, or scraper angle is too small caused by the scraper, at this time we should increase the scraper pressure and properly adjust the scraper angle. Re-imaging is not serious, you can improve the printing speed to solve the problem.
Sticky dirty
Sticky dirty is divided into the printing process of adhesion, scuffing dirty and printing back after the sticking of three kinds of cases. Adhesion is printed in the process of winding up after the back of a print adhered to the front of the previous print, so that the top and bottom of the 2 prints adhered together, resulting in damage to the prints. Dabbing dirty is the previous print ink film surface ink partially transferred to the back of the next print, so that the back of the next print has ink, the front of the previous prints into the front of the text of the blotchy. Sticky back is printed products in the process of placing the back of the phenomenon of sticky dirty.
The emergence of the above problems are caused by the printing of ink drying too slowly, or ink is not completely dry to appear false drying, solvent evaporation rate is low, too much residual solvent in the prints. In the production process can be appropriate to reduce the thickness of ink printing, improve the drying temperature, reduce the printing speed, improve the drying performance of the ink, and switch to a high rate of volatilization of solvents to solve the problem.
Overprinting is not allowed
Overprinting is not allowed to refer to the color graphics are not transferred to the substrate according to the provisions of the fixed geometric position, the outline of the color graphics overprinting accuracy does not meet the requirements of industry standards, resulting in the printing of the product graphics and the original deviation is large. Factors affecting overprinting inaccuracy are mainly paper, printing workshop temperature and humidity, drying temperature of the printing machine.
- Paper
Paper itself contains a certain amount of moisture, production is generally controlled at 6% or so, but when the temperature and humidity of the printing shop and the production of paper temperature and humidity is not consistent, the moisture in the paper will change to make the paper deformation, resulting in printing overprint inaccuracy. In this regard, the printing of paper can be placed in the printing shop a few days in advance, so that the paper fully adapted to the temperature and humidity of the printing shop, so that the paper deformation will be less printing to ensure that the printing overprint accuracy.
- Printing workshop temperature and humidity
Printing workshop should be relatively closed to maintain a relatively stable temperature and humidity to ensure that the paper is not deformed.
- Printing machine drying temperature In order to ensure that the printing ink can be thoroughly dry under the circumstances of reducing the drying temperature of the printing press, so that the paper in a small range of deformation.
Paper wrinkles
Paper wrinkles refers to the printing process due to pressure and other reasons, the paper to produce wrinkles wrinkled, so that the printed product has folds, affecting product quality. The main reason is that the pressure roller pressure at both ends is not balanced, or the pressure roller is damaged, in the process of rotation of the pressure roller circumferential surface in contact with the paper at both ends of the force is different so that the paper wrinkles. Printing should be the pressure roller at both ends of the pressure adjustment consistent, specific operations: printing machine generally have a pressure gauge, according to the pressure gauge instructions to adjust the pressure consistent; with a percentage meter to check whether the pressure roller is damaged, if damaged in time to replace; check all the force over the paper rollers, to ensure that all the over the paper rollers are in the same horizontal position.
Plate blocking
Plate blocking refers to the printing in the printing plate mesh hole in the ink by certain factors will be partially dry solid, ink transfer rate is reduced, the mesh hole is blocked more and more shallow, until the plate blocking condition occurs. Plate blocking after printing blurred graphics, print color inconsistency, can not well reproduce the original. Can reduce the ink drying speed, or increase the speed of the printing machine and ink drying speed to adapt to the double filtering ink to solve the problem of plate blocking in printing.
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