The printing method for whiteboard paper

　　Method for printing on whiteboard paper:

　　Box-type packaging decoration and printing products, such as cigarette pack outer wrappers, liquor boxes, and food containers, are often printed on 250–400 g/m² whiteboard paper or cardstock. Offset printers can handle paper up to a maximum thickness of 0.9 mm, though in most cases, the paper used typically ranges from just 0.04 to 0.3 mm thick. The key difference between whiteboard paper and coated, offset, or letterpress papers lies in their thickness. When printing on whiteboard paper using an offset press, numerous adjustments must be made—specifically to the machine’s paper feed system, impression mechanism, color sequence arrangement, and ink-water balance—to ensure optimal results.

　　Whiteboard paper printing

　　I. Adjustment of the Offset Printing Paper Feeding Section

　　1. When printing on whiteboard paper, the air volume for both the suction nozzle and the blowing nozzle in the paper feed section should be adjusted slightly higher.

　　2. For the paper separation nozzle and paper feed nozzle, replace the rubber rings with larger diameters and greater thicknesses. Additionally, the regulating pressure spring can be replaced with a 1.5 mm diameter steel wire. To ensure the paper feed roller remains stationary and feeding becomes smooth, remove the connecting pin between the paper feed roller cam and its shaft, or take off the roller on the rocker arm.

　　3. When printing on white board paper, the gap for the sheet-fed printer's two-sheet control should also be increased accordingly; additionally, the distance between the side guides and front guides' pressure fingers and the delivery table, as well as the distance between the safety bar and the delivery table, should both be slightly widened.

　　4. Increase the clearance between the delivery gripper pads and the surface of the impression cylinder, as well as the gap between the delivery gripper pads and the feed plate—ensuring each distance is approximately equal to the paper thickness plus 0.3 mm.

　　II. Roller Covering and Pressure Adjustment

　　When printing on white board paper, the center distance between the printing plate cylinder and the rubber cylinder remains unchanged—only the center distance between the impression cylinder and the rubber cylinder needs adjustment. For printing 250–450 g/m² white board paper, you can increase the cylinder center distance by 0.20–0.4 mm. Since white board paper has relatively poor surface smoothness and feels coarser compared to coated paper, its paper density is also significantly lower. Therefore, when printing on white board paper, be sure to slightly increase the printing pressure as well.

　　For example, with 400 g/m² whiteboard paper, the gap between the printing plate cylinder and the rubber cylinder is 3.95 mm, while the gap between the rubber cylinder and the impression cylinder is 3.40 mm. The total covering thickness of the printing plate cylinder is 0.65–0.75 mm, and the total padding thickness of the rubber cylinder is measured using a micrometer to be 3.15–3.35 mm. If the paper thickness decreases, you should remove the corresponding amount of padding—equal to the reduction in paper thickness—from the printing plate cylinder’s padding and add it to the rubber cylinder’s padding. Conversely, if the paper becomes thicker during printing, you’d subtract the extra thickness from the rubber cylinder’s padding and transfer that same amount to the printing plate cylinder’s padding instead.