Flexography
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This article is part of the series on the |
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| Technologies | ||
|---|---|---|
| Phaistos Disc | 1850–1400 BC | |
| Woodblock printing | 200 AD | |
| Movable type | 1040 | |
| Intaglio | 1430s | |
| Printing press | 1439 | |
| Lithography | 1796 | |
| Offset press | by 1800s | |
| Chromolithography | 1837 | |
| Rotary press | 1843 | |
| Flexography | 1890s | |
| Screen-printing | 1907 | |
| Dye-sublimation | 1957 | |
| Photocopier | 1960s | |
| Pad printing | 1960s | |
| Laser printer | 1969 | |
| Dot matrix printer | 1970 | |
| Thermal printer | ||
| Inkjet printer | 1976 | |
| Digital press | 1993 | |
| 3D printing | ||
Flexography (also called surface printing), often abbreviated to flexo, is a method of printing most commonly used for packaging (labels, tape, bags, boxes, banners, etc.).
A flexographic print is made by creating a positive mirrored master of the required image as a 3D relief in a rubber or polymer material. A measured amount of ink is deposited upon the surface of the printing plate (or printing cylinder) using an engraved anilox roll whose texture holds a specific amount of ink. The print surface then rotates, contacting the print material which transfers the ink.
The flexible printing plate used in the final ink printing stage is light sensitive. A positive is placed over the plate, and is displayed to ultra-violet light. The plate is then 'washed' on a rotating drum in a tank of Toluene solvent, which removes the layer of material that received the ultra-violet light.
Originally flexographic printing was basic in quality. Labels requiring high quality have generally been printed using the offset process until recently. In the last few years great advances have been made to the quality of flexographic printing presses.
The greatest advances in flexographic printing have been in the area of photopolymer printing plates, including improvements to the plate material and the method of plate creation, usually photographic exposure followed by chemical etching, though also by direct laser engraving.
Digital direct to plate systems have dominated the industry recently with their better resolution and the ability to print four color process (or more) as well as offset. Some companies who make plates in house are going to trade shops to get these high quality plates.
Laser-etched anilox rolls also play a part in the improvement of print quality. Full color picture printing is now possible, and some of the finer presses available today, in combination with a skilled operator, allow quality that rivals the lithographic process. One ongoing improvement has been the increasing ability to reproduce highlight tonal values, thereby providing a workaround for the very high dot gain associated with flexographic printing.
Flexo has an advantage over lithography in that it can use a wider range of inks, water based rather than oil based inks, and is good at printing on a variety of different materials. Flexographic inks, like those used in gravure and unlike those used in lithography, generally have a low viscosity. This enables faster drying and, as a result, faster production, which results in lower costs. Printing press speeds of up to 2000 FPM (600 meters per minute) are achieveable now with modern technology high-end printers, like Flexotecnica [1], a member of the Cerutti Group. Flexotecnica will introduce its highly automated F12 press at Drupa 2008.
[edit] Products
Typical products printed using flexography include brown corrugated boxes, flexible packaging including retail and shopping bags, food and hygiene bags and sacks, flexible plastics, self adhesive labels, and wallpaper. A number of newspapers now eschew the more common offset lithography process in favour of flexo.
[edit] In education
The Flexo in Education Program, formerly The Flexo in High School Program, was started at South Mecklenburg High School in Charlotte, North Carolina by the Flexographic Technical Association in 1993. Since its inception many other high school programs have been started. For example Asheville High School in Asheville, NC, The Applied Technology Center in Rock Hill, SC, Fort Mill High School in Fort Mill, SC, and others. The program has even gone international with the inclusion of Gordon Graydon Memorial Secondary School in Missasauga, Ontario Canada. The program was re-named to become the The Flexo in Education Program because post-secondary institutions began to participate in the program. Many technical colleges and universities incorporate flexography into their curriculum. For example The Department of Graphic Communications and the Clemson University Printing and Converting Research Center at Clemson University, Central Piedmont Community College, Chowan University, Appalachian State University, the Graphic Communications Management program at Ryerson University, and others include flexography in their curriculum.
[edit] Flexographic printing inks
The nature and demands of the printing process and the application of the printed product determine the fundamental properties required of flexographic inks. Measuring the physical properties of inks and understanding how these are affected by the choice of ingredients is a large part of ink technology. Formulation of inks requires a detailed knowledge of the physical and chemical properties of the raw materials composing the inks, and how these ingredients affect or react with each other as well as with the environment. Flexographic printing inks are primarily formulated to remain compatible with the wide variety of substrates used in the process. Each formulation component individually fulfils a special function and the proportion and composition will vary according to the substrate.
