Flexographic printing
Often referred to as flexographic printing, is used as a packaging printing . ü
Definition: the definition of the standard terminology of GB9851.4-90 printing , flexographic printing using flexographic , passing through the anilox printing ink .
Flexographic printing is on or polyester material to produce a desired image projecting mirror plate - like a potato print kids play . The amount of the ink to the printing plate ( or a plate drum) by the anilox roll control. During the rotation of the printing surface in contact with the printing material to transfer the graphic .
Flexography named because it was originally used for printing corrugated board surface is very uneven , it is necessary to keep the plate surface in contact with the board , so it should have good flexibility. Moreover , the high point of the printed board is not printed on the printing plate can not be residual ink , which requires non-image portion of the printing plate having a sufficient depth to be able to meet this requirement .
The original flexographic printing is very poor . In recent decades , improved methods and plate -plate printing plate material has been greatly improved - usually photographic exposure followed by chemical etching , now using direct laser engraving . Printing full- color images has become possible.
Flexo printing features
1 ) ink is a kind of alcohol as the main low-viscosity solvent evaporation drying type ink , fast drying, high-speed multi-color flexo printing adaptation . Pollution-free , fast drying water-based inks applied to bad environmental protection is extremely beneficial.
2 ) is a photosensitive flexographic printing plate of rubber or resin type , having a soft, flexible and resilient characteristics. Shore hardness generally 25 to 60, the ink transfer properties of good , especially for the alcohol solvent ink. This is a Shore hardness of 75 or more stereotype , plastic version can not be compared .
3 ) the use of light printing press for printing.
4 ) for flexo printing material is very extensive.
5 ) good print quality . Due to the high quality of the resin version, ceramic anilox and other materials, the printing precision has reached 175 lines / in, and have full ink film thickness , so rich product level , colorful , particularly suitable for packaging printing requirements, the eye-catching color effects are often offset lithography can not be achieved . It is clear both letterpress printing , offset printing soft colors, gravure ink thick and high gloss.
6 ) high production efficiency. Flexographic printing equipment usually roll type material that can be printed from the double-sided multicolor to polishing, coating , bronzing, die-cutting , license fees , rewinding or slitting a continuous process is complete. In offset printing often use more personnel and more than one device can be done in three or four steps . Therefore , flexographic printing can greatly shorten the print cycle , reduce costs , allowing users to take advantage in a highly competitive market.
7 ) Easy operation and maintenance . Printing using anilox inking system, compared with the offset and letterpress machines , eliminating the need for complicated inking mechanism , so that the operation and maintenance of the printer is greatly simplified , and the inking control more responsive . In addition , the press in general with a set of repeat length can be adapted to different printing plate cylinder , specially adapted specifications change frequently packaging printed .
8 ) Printing speed is high. Printing speed is generally 1.5 to 2 times the offset and gravure printing machine to achieve a high-speed multi-color printing.
9 ) low investment and high returns. Modern flexo ink transfer route segments with ink transfer fewer parts , plus the advantages of flexographic printing presses and other very light pressure , making flexo simple structure , processing the materials used to save many . Therefore, investment in machinery is much lower than the same color offset press group , 30% to 50% of the group is just the same color gravure printing machine investment.
Flexo platemaking features: on the plate , flexo platemaking cycle is short , easy to transport , the cost is much lower than the gravure . Although the plate offset printing PS plate several times higher than the cost , but can be compensated for in the resistance rate , because the rate of flexographic printing resistance printed in 500,000 to several million printing ( offset printing anti-Indian rate of 10 to 30 million impressions ) .
The system features flexographic printing
1 ) Compared with gravure and offset printing , flexo density curve instability, changes in plate thickness equal print quality has a greater impact , which increases the difficulty of flexo color overprint .
2 ) flexo printing using anilox ink transfer , printed version must match the network cable and line number anilox roll , otherwise it will cause a small point of light district into a high hole printed ink does not come out , and the four-color version of the screen angle can not be using 45 °, or easy to produce moire .
3 ) Dot gain is more serious, because of the low hardness flexographic , graphic easily deformed by extrusion, printing process dot gain more serious . A general increase in the range of 16% -30 % , midtones up to 50 %, with 2% -3 % of the network increased to 15% or even higher. Therefore, the print is difficult to guarantee the tone level , resulting in the entire edition level to high-profile development , part becomes darkened spot , dot appears hollow , not smooth . Network -level changes would cast serious picture , the whole picture looks level is unknown , unclear , difficult to express subtle level , three-dimensional sense is not strong. In the dot gain influence , flexographic printing out the image 10% below the high level of serious loss of light , more than 85% level easily become darkened field .
4 ) Because flexographic printing pressure is small, a slight change in pressure will produce significant changes in the quality of the printing , embossing force control becomes very important.
5 ) the need to re- set the color separation parameters can not copy offset or gravure . At present, China imported mostly unit -type flexographic printing equipment , units generally have 6-8 , plus more spot-color packaging industry , therefore , to consider the separation flexo on multicolor separations to compensate for printing inadequate access point performance.
6 ) After the rational design process . Flexo printing unit more, plus multi-channel online after processing, to put forward higher requirements overprint , so when flexo platemaking , while the design process on how to become a major difficulty .
7 ) flexo dot gain is nonlinear , and that this change is not proportional to the dot area . Dot gain is equidistant offset , flexo printing plate and the smaller the access point , in the printing area due to a small force , the larger the lateral outlets after the deformation force increases more serious. This is to be opened with flexo color and tone contrast requirements opposite. Flexo dot trend was as follows : In the very hour outlets , either absolutely Network ( copy caused ) ; either increased to 15 % or more outlets ( print result ) . In the darkened part of the network can easily become the site ( copy and print result ) .
8 ) flexographic pasting distortion compensation means. The most obvious feature is the flexible flexographic , a system has been very flexible printing plate perfect , when it is mounted to a cylindrical drum , drum lines along the surface of the plate will produce circumferential bending deformation , this deformation will involve graphic plate to the surface , making the graphics and printing out the document size deviations occur . For less demanding print quality , can not be considered , but for higher print quality requirements , measures must be taken to compensate for changes of this size , there are ways to compensate for the following categories:
a) In the original design, based on the printing plate elongation , changing the size of the corresponding values subtracted .
b) copy when shooting film, shot using a deformable mirror , shortening change to size.
c) the use of computer plate , just finished design draft ink separations before zooming to a single instruction .
d) the use of the drum type copy method , i.e., the same printing plate cylinder and proofing plate cylinder size.
