The differences between letterpress printing and flexographic printing are mainly reflected in the characteristics of the printing plate, ink and ink transfer system, printing effect and applicable scenarios, operation and maintenance, and environmental protection. The following is a specific analysis:
Different characteristics of printing plates:
The text and image part of the letterpress printing plate is raised, and the hardness is relatively high. Traditionally, lead type and woodcut plates are commonly used. Modern ones mostly use photosensitive resin plates. The thickness is generally less than 1mm. Common specifications are 0.8mm and 0.95mm. The hardness of the finished printing plate is usually around 90 degrees Shore.
The text and image part of the flexographic printing plate is also raised, but the material is softer and more elastic. Photosensitive rubber or resin printing plates are used. The thickness is generally between 1 and 5 mm, and the hardness is between 30 and 70 degrees.
Different ink and ink transfer systems:
Letterpress printing uses paste ink with a certain viscosity. Through a complex ink delivery system, including an ink fountain, an ink fountain roller, an ink transfer roller, an ink string roller, an ink roller, etc. (a long ink path system), the ink is evenly transferred to the printing plate.
Flexographic printing uses low-viscosity, high-fluidity liquid ink and adopts a short ink path system to transfer ink through anilox rollers. The anilox roller is both an ink transfer roller and an ink metering roller and can accurately supply ink according to process requirements.
The printing effect is different from the applicable scenario.
The ink color of letterpress printing is thicker, the ink layer thickness is about 7 μm, the back of the printed paper has slight raised marks, the edges of the lines or dots are neat, the ink appears light in the center, the raised edges of the prints are under heavy pressure, the color reproduction is average, and it can be printed on rougher substrates. It is often used for book printing, trademarks, packaging and decoration printing, newspaper printing, etc.
Flexographic printing has a full ink layer thickness, rich product layers, bright colors, and a printing accuracy of up to 175 lines/in. It is particularly suitable for scenes with high requirements for color and layers in packaging printing, such as flexible packaging (food bags, shrink films, etc., about 70% of flexible packaging uses this technology), corrugated boxes (about 90% of corrugated boxes use this technology), label printing (such as beverage bottle labels), sanitary products (tissue packaging), and some publications (such as newspaper inserts).
Different operation and maintenance:
The structure of letterpress printing presses is relatively complex, and operation and maintenance are difficult.
The structure of flexographic printing presses is simple, easy to operate, and easy to repair and maintain. The price of a flexographic printing press with the same function is about 30-50% of that of an offset or gravure printing press.
Different environmental protection:
The paste ink used in letterpress printing may have certain disadvantages in terms of environmental protection compared to the liquid ink used in flexographic printing.
Flexographic printing can use non-polluting, fast-drying, water-based inks, which are extremely beneficial to environmental protection and meet the increasingly stringent environmental protection regulations.
