Toppan printing paper craft quality control

Whiteboard paper is a commonly used printing material for packaging and decorating with the advantages of tough texture, smooth surface, folding resistance and impact resistance. Toppan printing has the obvious advantages of thick ink layer, high brightness, and vivid colors, and is suitable for printing whiteboard paper products. However, to print whiteboard, the control of process technology is very important.

First, scientific and reasonable use of printing equipment to control the printing speed

Whiteboard paper packaging prints are generally multi-color overprinting and overprinting of large-area layouts. The uniform color, bright color, and accurate overprinting are the basic requirements for the color printing process of whiteboard. To meet these requirements, there are two types of press models that are more appropriate. One is a round flat type four-color single-color, two-color automatic platform printing machine, such as TY401 type four open automatic rotary platform printing machine, OT400 type four open automatic platform printing machine, etc.; second is a round press circular structure printing machine, such as TL2640 double color letterpress rotary press. The latter has advantages over the former in terms of production efficiency, printing speed, printing format, ink quality, and overlay accuracy. Although the speed of the platform printer can reach 4,000 sheets/hour and the speed of the rotary press can reach 6,000 sheets/hour, when printing large-area gradation and field version products, it is not appropriate to open the printing speed to more than 3300 sheets/hour. Because the speed is too fast, the instant imprinting time is relatively reduced, and the amount of ink transfer is small, and the visual effect requirements of the ink layer of the printed product cannot be satisfied. In addition, excessively high speed will cause the frictional heat of the ink fountain roller and the rubber roller to increase significantly, and the ink tends to be thin and fade due to thixotropy. In both cases, it is necessary to increase the amount of ink transferred to solve the problem, and an increase in the amount of ink transferred can easily lead to paste, sticky paper powder and other ills. If white paper of 350g/m2 or more is printed, the speed is too fast and the time for drawing and delivering the paper is relatively reduced. This can easily lead to malfunctions such as empty sheets and improper delivery of paper. Therefore, the speed of printing whiteboard paper is controlled at 2400-3000 sheets/hour.

Second, correctly adjust the printing press and its attachments

1. Adjust the printing pressure

Due to the thicker white paper, if the machine is originally set for the pressure of thin paper, then when printing white paper, the printing pressure of the machine will obviously be too large, and the pressure should be reduced. There are three ways to adjust the pressure of letterpress printing: firstly, feeding or reducing the base layer of the printing plate; secondly, adding or subtracting padding to the lining of the rubber roller; and thirdly, raising or lowering the pressure roller. The first and third pressure adjustment methods should be adjusted within the technical parameters of the equipment; otherwise, overprinting will be inaccurate due to inconsistent line speeds. The principle of the second pressure adjustment method is to reduce the thickness of the lining, so that the surface of the printed sheet is flush with the shoulder surface of the drum, which is not only favorable for printing registration but also avoids other ills. Therefore, in the case where the thickness of the substrate is significantly increased, the purpose of adjusting the printing pressure should be achieved by thinning the lining accordingly, so that the height of the printing plate is maintained within the numerical range specified by the equipment.

2. Adjust the feeding device

Whiteboard paper is hard and thick. If the paper feeding system is not normal, it will cause some problems. Therefore, relevant parts and components should be properly adjusted. The clearance of the side plate should be adjusted so that the white plate paper is not under the pressure resistance, which ensures accurate positioning of the printed sheet. According to the thickness of the printed sheet, the gripping pressure and opening gap of the gripper and delivery teeth are adjusted. , Angle, so that the printed sheet delivery, positioning, stability and accuracy; in the paper feeding area of ​​the suction and blowing volume should be adjusted more, if necessary, should also replace the suction nozzle rubber sheet size to ensure continuous normal feeding; on loose paper steel The bending length and angle of the sheet are adjusted accordingly to reduce the double-sheet phenomenon; according to the thickness of the sheet, the double-sheet controller is adjusted accordingly to prevent double sheets and multiple sheets from entering the imprinting mechanism and damaging the printing plate.

Third, a reasonable selection of plates to improve the printing plate resistance and printing quality

When printing a large-area gradation or field version on a whiteboard, the required printing pressure is relatively large. If a copper-zinc plate is printed on a wooden tray, the printing ink may be easily discolored, and the printing plate may also be easily damaged by cracks. Therefore, flexible resin plate printing whiteboard paper products should be selected. The required printing pressure is light, the ink color is uniform and full, the printing plate is resistant to printing force, and the product quality is good.

If the layout background is solid, the offset blanket can be cut directly to the corresponding area and pasted on the cylinder for printing. The use of a blanket as a printing plate has the following advantages:
(1) Due to the smooth surface of the blanket, soft texture, and good ink receptivity, the printing ink can be uniform and thick.
(2) Since the surface of the blanket is soft and has a certain viscosity, the ink roller is not slippery during the operation to avoid the occurrence of a stick mark.
(3) The blanket material is soft so that the printed product does not have bulges on the edge of the layout, and the printing plate has high resistance to printing and the product quality is good.
(4) The soft rubber blanket can not only be made into a square solid version, but also can be manually cut out with a corresponding punching knife (die) or utility knife according to the layout design requirements. The production method is simple and fast. .

Fourth, a reasonable arrangement of printing color order to ensure product quality

Printing color sequence has a direct impact on product quality. Arrangement of color sequence should be considered from the following perspectives:
(1) In order to prevent the imprinting of the ink on the imprinted layer, the text, line, and pattern are usually printed first, and then printed in full.
(2) From the perspective of ease of overprinting, it is advisable to print dark colors first and light colors after printing. Based on the speed of drying of the ink, the ink may be dried and the ink may be brightly colored and the gloss may be high. Therefore, the ink with the slower drying speed is first printed, and the ink with the faster drying speed is printed.
(3) Considering the transparency of the ink and its color rendering effect, the color of the ink layer below can be transmitted through the upper layer of ink film after being superimposed and mixed into a more vivid color, so the transparency is poor. The ink is printed first, and the ink with good transparency is printed.
(4) From the viewpoint of the viscosity of the ink, the ink with the generally high viscosity is printed first, and the ink with the lower viscosity is printed.
(5) Considering the area of ​​printed graphics, small areas should be printed in advance and large areas should be printed. Level and field products, generally printed in the first edition, after printing the field version.

V. Anti-sticking process control of printed products

White paper has a smooth surface, and the paper is both thick and hard. During printing, if you do not pay much attention, you may easily get stuck and affect product quality.

During air-drying, products should be stacked vertically and horizontally to make the surface of the paper vertical to the ground. Heavy pressure does not form between the printed sheets to avoid the occurrence of bottoming.

If you print a large area on the ground layout or overprint layout, consider adding appropriate drying oil in the ink to urge the ink layer to prevent dirt. If antifouling is used, it should be thin and uniform; the air path should be kept clear and the powder should be dry and loose, which is a crucial technical control link. Addition and release of anti-adhesive agent to the ink is also a good measure to prevent sticky dirt, however, the usage and usage should be carefully grasped. Add an appropriate amount of bright oil to the anti-sticking agent and mix it evenly. Then add the paste-like anti-sticking agent to the ink and mix well. This will make the anti-adhesive dirty effect better. The amount of anti-adhesive agent is generally not to exceed 4%, so as to avoid the occurrence of ink emulsification, ink layer flowering and gloss degradation and other undesirable phenomena.

In summary, through the control and control of the process technology, not only the occurrence of various undesirable phenomena can be avoided, but also the product quality can be improved.

Source "Printing Technology"