How to print white paper
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Box packaging and decoration printing products such as cigarette case packaging, wine boxes, food boxes, etc., are often printed with white paper or card paper of 250-400g/m2. The maximum paper thickness that the offset printing machine can print is 0.9mm, but generally In the case of paper, the thickness of the paper to be printed is often only between 0.04 and 0.3 mm. The difference between whiteboard paper and coated paper, offset paper and letterpress paper is the thickness of the paper. In the process of offset printing of whiteboard paper, the paper feeding part of the offset printing machine, the embossing part, the color sequence of the printing, the ink balance and the like are all Adjust accordingly.
First, Roller lining and pressure regulation
When the whiteboard paper is printed, the center distance between the plate cylinder and the blanket cylinder is unchanged. It is only necessary to adjust the center of the impression cylinder and the blanket cylinder. The 250-450g/m2 whiteboard can enlarge the center distance of the roller by 0.20-0. .4mm, because the smoothness of the surface of the whiteboard paper is relatively poor and rough, the tightness of the paper is far less than that of the coated paper. When printing the whiteboard, pay attention to the pressure of printing.
For example, 400g/m2 of whiteboard paper, the gap between the plate cylinder and the blanket cylinder is 3.95mm, the gap between the blanket cylinder and the impression cylinder is 3.40mm, and the total package of the plate cylinder is 0.65-0.75mm. The total pad of the blanket cylinder is 3.15-3.35mm (measured with a micrometer). If the paper is thinner and thinner, the reduced thickness should be added to the thickness of the liner removed from the plate liner. In the blanket cylinder, if the paper during printing is turned from thin to thick, a certain thickness is subtracted from the blanket cylinder liner, and the corresponding thickness is added to the liner of the plate cylinder.
Second, the adjustment of the offset paper feeding part
1. When printing whiteboard paper, the air volume of the paper feeding part and the paper blowing nozzle of the paper feeding part should be adjusted accordingly.
2. The paper separation nozzle and paper feed nozzle should replace the rubber ring with larger diameter and larger thickness. The tension spring can be replaced with a wire with a diameter of 1.5mm. By removing the paper feed roller cam and its shaft The coupling pin or the roller on the swing rod is removed to achieve the purpose that the paper feed roller does not swing and the paper feed is stable.
3. When printing whiteboard paper, the double control or clearance of the offset printing machine should be increased accordingly; the distance between the side plate and the front gauge paper tongue and the paperboard, and the distance between the safety bar and the paperboard must be Increase some.
4. The distance between the transfer pad and the impression cylinder surface and the transfer pad and the transfer paper should be increased, and the distance should be approximately equal to the paper thickness plus 0.3 mm.
Third, the color sequence arrangement during printing
1. The products printed on whiteboard paper are in Hong Kong version, with text, lines and patterns. Such as: the postal department's express mail envelope, wine box, cigarette case packaging (bar box) and other printed products, the color sequence of printing is best printed text, lines, patterns, and then the full version of the field on the final machine printing In this way, it is possible to avoid the dirt rubbing and the back side being dirty due to the thicker white paper and the paper colliding with each other when the print is not dry.
2, the dark color is placed on the front, the light color is placed on the back, because the dark color of the ink has strong hiding power, strong adhesion, first placed in front, easy to overprint; shallow color ink hiding power, When you put the print on the back, it is not easy to observe the rules. The effect of overprinting is much better.
3, often in a printed product, there are halftone four-color electricity points, and there are continuous tone patterns, text, lines. The four-color electric sub-network should be printed first, which is conducive to accurate overprinting and reduce the impact of paper stretching. Then print the pattern, text, and lines continuously, and look for the primary and secondary in the arrangement of the printing color sequence.
4. If the weather is hot, when the white paper is printed in monochrome, the water content of the paper is uneven, the wrinkles are not flat, and the surface strength of the paper is poor, such as powder, hair loss, etc., you can also first print a water, you can Solve the phenomenon.
Fourth, how to prevent whiteboard printing
1. When printing the full version of the field, try to use the original barrel ink, do not add 6# tempering oil, add some de-adhesives and anti-adhesive agents; do not add dry oil when the weather is hot. The printed version is often easy to stick on the back, often by dusting. Although the printed anti-stick dusting powder contains pure plant material, the dispersibility and fluidity are good, but the use of powder spray directly affects the printed product. The surface gloss makes the ink color not bright, and pollutes the environment, and has an impact on the accuracy of the offset printing machine.
2. The surface of the whiteboard paper is rough, the quality is loose, the ink absorption is large, and the flatness is poor. Therefore, when printing the full version, the background color should be printed first, and the back color should be darker. The bottom color should be darker, the printing is thinner, and the ink color should not be too Big. If the flatness of the whiteboard paper is good, then the printed version should be printed with a deep color first, and the ink is printed on the back, and the back is not sticky, and then the bottom color is printed thinly, so that the printed product finish will be compared. Ok, at the same time, pay attention to the ink balance and control the water size of the printing plate.
In addition, when the offset printing machine prints whiteboard paper, because the paper is thicker, multiple whiteboard papers are jammed into the embossing and the blanket cylinder, which is easy to cause "boring car", so it is necessary to carefully and carefully control the double sheets before printing. The device for control, pre-rush control and other electrical appliances is properly adjusted. The distance between the double control wheel and the paper feed roller during double-sheet control should not be less than two paper thicknesses, but it should not be greater than three paper thicknesses, otherwise the arched paper passes. When the controller is stopped, or the double sheets have passed through the controller, and the two contacts of the controller power supply have not been touched, and the purpose of controlling the double sheets cannot be achieved. Clean up the dust or dirt on the surface of the double control wheel and the paper feed roller, or the surface of the two contact surfaces at the power control control in time to prevent the double control system from malfunctioning, and the “smuggling car”, the rubber roller and the pressure A malfunction of the print cylinder occurred.