Factors Considered in Plate Making Design
Due to the flexibility and certain elasticity of the flexographic plate material, and its relatively large thickness, when it is adhered to the cylindrical plate cylinder, the longitudinal surface of the plate corresponding to the circumferential surface of the cylinder will undergo a certain bending deformation. This is especially pronounced for thicker plates, where the coefficient of surface deformation increases after pasting. Consequently, the graphics on the printed plate may deviate from the original size. For halftone structure printing plates, the enlargement deformation of halftone dots is a major issue causing color deviation in printing. Therefore, the technical control in the plate making design phase for flexographic plates has a significant impact on printing quality.
In plate making design, it is necessary to adjust the plate size appropriately based on the elongation rate of plates with different thicknesses, considering the material characteristics, to avoid the printing plate size exceeding the original manuscript size. For the printing of halftone plates, compensation for dot enlargement should be made by adjusting the flexographic plate's color separation characteristic curve before outputting. For products with barcode plates, during imposition design, efforts should be made to align the direction of barcode lines with the circumferential direction of the cylinder to avoid deformation affecting normal use.
Due to the difficulty in achieving good reproduction of fine dots in the plate making and printing process, especially the loss of highlights, and the tendency of soft plates to expand and blanket in the dark tone dot areas under pressure, dot enlargement deformation will result in a lack of depth in the printed surface, leading to a noticeable decrease in print quality. Therefore, the design of dot tonal adjustment and line count should be reasonably determined based on the hardness of the substrate and the glossiness of the surface. Generally, for soft and less smooth substrates, the dot size in high-gloss areas should be appropriately increased, typically designing high-gloss areas with dots not less than 4%, while controlling dark tone dots within 85%. The additional line count of the printing plate depends on the quality of the printing material. For corrugated cardboard, the additional line count is significantly less than that of pre-printed cardboard surface paper. When using high-quality coated whiteboard paper and advanced flexographic plate equipment, the plate's line count can reach 175 lines/inch or even higher. In addition, it is not advisable to design overly fine lines and small text on flexible plates to avoid causing plate fouling and affecting print quality.