Question

What is the Flexographic Printing - What is flexographic printing??

Accepted Answer

A method of printing  this process creates an image through relief printing  using flexible plates to form a raised negative of the image  which is inked and then transferred onto the substrate using pressure  Also known as flexography or    flexo    printing  flexographic printing is a modern form of letterpress printing that uses flexible rubber or photopolymer plates to create a raised image that can be transferred onto a wide variety of materials         There are three stages to flexographic printing  plate making  mounting  and printing  The image carrier in flexographic printing is a flexible plate  or plates  that is attached to the plate cylinder  which is usually made of steel   There are three ways to produce these plates  with each one requiring a particular material or materials to be used to make the plates  The earliest form of flexographic printing used natural rubbers to make plates  while most modern flexographic printing uses synthetic rubbers  These plates are created using a moulding process  a negative of the image is created on a metal plate  early plates used zinc  before being replaced by magnesium   which is then used to make a mould in plastic or glass  which becomes the master mould for the rubber plate or plates that will be used for printing  More commonly  plates are made using a photopolymer  this is a light sensitive organic substance that undergoes polymerisation when it is exposed to light  To produce a photopolymer plate  a photographic negative of the image being printed is placed over the photopolymeric material  which can be in solid or liquid form  and exposed to UV light  The areas that are exposed  image  undergo polymerisation and harden  while the areas that are covered  non-image  remain soft and soluble  the material is washed and brushed  which removes the soft areas and leaves the negative of the image on the plate in raised form  Finally  some flexographic printers use design rolls  which aren't  strictly speaking  plates but they do perform the same function     carrying the image     as rubber and photopolymer plates do   a layer of vulcanised rubber is applied to the plate cylinder and a negative of the image is created using a laser  which removes the non-image portions of the rubber surface  This is known as digital platemaking and is usually used to print a continuous pattern or design because the roll doesn't leave a seam as individual plates do  Where rubber or photopolymer plates are used  the second stage of printing involves mounting the plate  or plates  onto the plate cylinder  or cylinders   usually by means of an adhesive backing  before printing can begin         Flexographic printing can use a variety of inks  although they do tend to be volatile  quick drying liquid inks  they dry through evaporation of the vehicle and are well suited to high volume  high speed printing  which requires quick drying inks to avoid smudging  Ink is usually transferred from an ink fountain in one of two ways  a fountain roller can transfer ink from the fountain to the anilox roll or the anilox roll can pass through the ink fountain itself  with any excess ink being removed by a doctor blade that passes across the anilox roll  The anilox roll is made of an engraved metal or ceramic and its surface has hundreds or thousands of cells per inch  ink collects in the cells with either the fountain roller or doctor blade controlling the transfer of ink to reduce printing defects such as pinholing  A doctor blade is usually chosen over a fountain roller when there is a requirement for high speed printing  The anilox roll then deposits ink onto the plate cylinder  with the raised areas  image  being inked while the recess areas  non-image  remain clear  The substrate is then fed between the plate cylinder and an impression cylinder  usually made of steel   which uses pressure to transfer the ink  and therefore the image  onto the substrate  the use of a plate cylinder  or image cylinder  and an impression cylinder means that flexographic printing is a form of rotary printing  and requires a rotary printing press   While this process tends to use quick drying inks anyway  UV inks can also be used to further speed up the drying process and prevent smudging         This method of printing is capable of full colour prints  each colour requires its own colour station and flexographic presses can have between two to eight colour stations  although they usually have six   each of which has its own ink fountain  fountain roller  plate cylinder  and plate   and impression cylinder  These colour stations can be arranged in three different ways  a stack press stacks the stations vertically  making them easy to access and allowing both sides of a substrate to be printed   a central impression press arranges the stations in a circle around the impression cylinder  producing high quality print but only on one side of the substrate   and an in-line press places the stations horizontally  allowing thicker substrates to be printed on and  if a turnbar is used  allowing both sides to be printed   Great care needs to be taken when printing multiple colours because  if any of the different plates are misaligned  the colours won't align correctly to form the final image         Flexographic printing has undergone a number of developments that have brought it a long way from the earliest presses that were first used in the late 19th century  the 20th century saw great a number of advances in the production of printing presses  printing inks  and printing plates  and the materials they could be made from   It is a web fed process  it isn't suitable for individual sheets  and  due to its use of flexible plates and its ability to print using a variety of inks  it is capable of printing onto a large range of materials including plastics  foils and metallic films  acetate film  cellophane  paper  polyester  polyethylene  polypropylene  polystyrene  vinyl  and latex  some of which other printing processes cannot print on well or at all   This makes flexographic printing a popular process for printing items such as packaging  corrugated boxes  shopping bags  food packaging  drink cartons  disposable cups and containers  wallpapers  newspapers  envelopes  and labels  Its use of fast drying inks allows printing to be done much more quickly  which reduces overall production costs and makes flexographic printing ideal for high volume printing  It is also capable  with some care  of producing high quality print that comes close to the print quality of lithographic printing  although it can usually be distinguished from other forms of printing by a slight halo effect around the outline s  of the printed image

Letterpress Printing - What is letterpress printing?

Definition of LETTERPRESS PRINTING: