Flexography Printing Process

Overview:

Flexography uses Relief printing process, in which there is a raised surface to hold the ink. Ink roller takes the ink from the ink pan and applies it over the raised surface, or by pressing the plate against the inking pad. The first plates produced by relief method were made by hand from wood. And later, the presses were engraved into metal and used movable metal type.

Plate-making:

The printing plates are made using rubber, photopolymer or sometimes by metal, as it depends on type of application. The oldest form of flexographic plate were made by rubber, and it is now declining as science and technology have progressed. Most of the modern flexographic plates are now made up of photopolymer, a material that cures/hardens when exposed with ultraviolet light (UV light). Unexposed areas are soluble and can be washed away. This exposure and non-exposure helps forms the image and non-image area over the photopolymeric printing plate.

Nowadays, an evolving  ablation technology using digital CTP (computer-to-plate) is replacing photo negative based imaging. Photopolymer plates are capable to hold smaller screen than rubber plates and produces quite better process art images.

Another Laser Engraving process is able to engrave rubber sleeve mounted on metal to produce seamless cylinder. This method is used where continuous repeat is required.

Printing Process:

• The ink being transferred from ink roll, which is partially immersed in ink tank. 
• Then it transfers to the anilox roll that meters ink to the printing plate in uniform thickness 
• To avoid smudgy look, the excessive ink is scraped using a scraper called a doctor blade. 
• The doctor blade removes excess amount of ink from anilox roller before application of ink is made on printing plate. 
• The substrate is sandwiched between plate and impression cylinder for image-transfer.
• The sheet is printed with UV Curing ink, the and passed through UV chamber to be cured by UV rays.  

Image credit: Galus Australis