Using corrugated printing on corrugated cardboard paper can achieve vivid colors and delicate levels, but there are also some problems. In order to obtain the perfect results, you need to comprehensively consider the aspects of prepress design, printing, and postpress processing. This article summarizes the relevant common problems and precautions.
Problems related to design
When printing corrugated cardboard paper with an offset printing press, the design requirements are relatively loose, but the following points need attention.
(1) Continuously adjust the density of the pattern to be uniform, and distinguish the hanging angle according to the color. The main body color should be the primary color or the inter-color. If you can use the spot color, do not design it as a multi-color overlay.
(2) If there is a large area of overprint, do not design fine patterns or text with overprinting. If you need hot stamping, the design of the hot stamping area should not be too large, so as not to cause the stamping leak due to false pressure; hot stamping text should not be too small, otherwise it will paste, paste version. The need to print gold is generally designed so that a layer of uniform background color is printed first.
(3) Avoid designing long strips in the printing direction so as not to cause the surrounding blanks to be affected by the long edge printing under the action of the ink string ink.
(4) Avoid designing large areas of deep dark shades on the ground because the thickness of the offset ink layer may not be as thick as screen printing. If the deep darkness of the design is to be achieved, it may be printed twice. This will give printing and printing. Post processing brings trouble.
(5) The bar code should not be overprinted during design, and the bar code should be placed in the middle of the layout or close to the mouth when making the layout. The corners or wrinkles are likely to appear on the left and right corners, especially the carton face paper with large printing area. This is especially noticeable, which can cause ghosting and distortion of the bar code. Moreover, the bar code line direction should be the same as the printing direction as much as possible because the press deformation of the blanket in the printing mainly occurs in the printing direction. Finally, note that after the box is placed, the bar code should be located on the back or side of the carton.
Problems related to printing
1. Printing failures related to offset printing presses
When printing corrugated cardboard paper with an offset printing press, there are many printing failures related to the offset printing press and can be summarized as the following.
(1) Imprinting is not allowed. There are many reasons for overprinting, such as machine overprinting accuracy is not enough, should be overhauled; blanket loosened; plate plate clamps loose; paper sheet transfer between the unit is not stable; delivery paper teeth open, bad teeth closed; open Closed tooth spring breaks or the oil eye is lack of oil, rust dies; in front of the paper into the machine, the front edge of the paper is not uniform, or both ends of the paper passively enter into the tusks, and after entering the unit, the paper that has passively entered the cavities is displayed equally.
(2) Water bars and ink bars. It is generally caused by the uneven contact pressure of the water roller and the ink roller. In addition, check whether the bearings of the ink roller and the water roller are stuck or intermittent. Printing also pay attention to the control of ink balance.
(3) Dots increase or decrease, or even lose. Should start with the following aspects to check and solve: whether the pressure is appropriate; whether the blanket is aging or crushed; printing cylinder roller cylinder wear or foreign objects such as grease. The regular dot gain may be missing gear teeth or iron scraps or foreign objects between teeth; roller bearing damage, making the net point increase horizontally and then shrinking; poor elasticity of the blanket, or printing pressure is too high Exceeding the elastic limit of the blanket, the dots will sometimes increase, sometimes shrink or lose, and the blanket and liner should be replaced; while there are too many ink dirt or foreign objects on the pillow, or the blanket is too wide, one end is high In the case of rolling pillows, pressure imbalance will result, resulting in an increase in the number of dots on one end and a decrease in the number of dots on one end.
(4) Stick dirty flowers. Due to the high basis weight of corrugated box paper, it is generally 180g/m2 or more, high stiffness, poor winding, but strong resilience, easy to produce sticking phenomenon, therefore, in the printing unit should be positioned according to the die cutting position Anti-punching device, if necessary, can also be used to place a sponge mat on the paper transfer roller corresponding to the ink-less or less-inked part. In addition, due to the high basis weight, the phenomenon of paper falling from the tusks during printing is also more common. Therefore, when adjusting the front gauge, it must be ensured that the paper feed is smooth, and after the paper has fully entered the front gauge, it is pressed and printed again. Adjust the enthusiasm for a good collection of teeth. Because the reverse side of the carton face paper is gray-backed paper, poor flatness, pay attention to the back of the delivery and stacking paper sticky, can increase the amount of dusting, and control the pile height, so that the delivery as tidy as possible.
