Label printing machines (flexography) are one of the most useful tools in the category of printing machines because of their ability to produce high-end graphics for labels at a rapid speed. They are also the least expensive and simplest of the printing processes used for decorating and packaging printing. Essentially, flexography is a modern version of letterpress printing that can be used on almost any type of substrate, such as corrugated cardboard, cellophane, plastic, beverage cartons, newspapers, wrappers, label stock fabric, metallic film and many more. The process uses quick-drying, semi-liquid inks, and is especially advantageous because of its capability to handle large packaging or labeling orders.
Typically, printing is achieved by feeding the substrate into the press from a roll. The image is printed as the substrate is pulled through a series of stations, or print units. These flexible photopolymer printing plates, which are wrapped around rotating cylinders on a web press, are what control the flexographic printing process. The plates rotate at high speeds to transfer the image to the substrate, making them well suited to print continuous patterns, such as gift-wrap and wallpaper. Unlike the individual sheets of paper used in offset printing, the large amount of material that can be used during flexography allows sizeable orders to run without interruption.
Images are prepared by using camera-ready art/copy or electronically produced art supplied by the customer. The images are then captured for printing by camera, scanner or computer, and the components are assembled and positioned in a printing flat when a camera is used – a process called stripping. When the image is scanned or digitally captured, a computer with special software can assemble it. A proof is prepared to check for positioning and accuracy, and when color is involved, a color proof must be approved by the customer.
The inks used in flexographic printing consist of colorants, and can be water based, solvent based or U.V. curable. Water and solvent based inks use various types of alcohol as the primary drier, since alcohol rapidly dries through evaporation and contributes to VOC emissions. UV flexo inks are commonly used for topcoats and lacquers, and are responsible for many improvements in image quality of flexographic printing.
Despite the fact that printing plates can be expensive and the machine can take a rather long time to set up (typically several hours for a more complex job), the plates and machine will last for millions of impressions if properly cared for. There are also several other advantages to purchasing a flexographic label printing machine.