Principle and process of embossing

Embossing is the oldest printing process .

The printing principle is to make a raised printing plate first , Then apply ink to the printing , Finally, transfer the ink onto the paper .

The earliest movable type printing in China , It belongs to embossing .

         

The principle of letterpress printing is relatively simple . In relief printing , The ink feeding device of the printing machine first makes the ink evenly distributed , Then transfer the ink to the printing plate through the ink roller , Because the graphic part on the relief plate is much higher than the non graphic part on the printing plate , therefore , The ink on the ink roller can only be transferred to the graphic part of the printing plate , There is no ink in the non graphic part .

 

The paper feeding mechanism of the printing machine transports the paper to the printing part of the printing machine , Under the joint action of the printing plate device and the imprinting device , The ink of the graphic part of the printing plate is transferred to the substrate , So as to complete the printing of a printed matter . 

 

The paper back of any printed matter has a slight impression bulge , Lines or dot edges are neat , And the printing ink is light in the center , It is relief printing . The raised image edge is under heavy pressure , So there is a slight impression bulge .

With the emergence of offset printing technology , In the production process of many printing products , The embossing process is no longer used , But it does not mean that embossing has been eliminated , Embossing technology is developing with the times , One of the new branches is the adoption of “ Ceramic anilox roller “ Resin version ” Ink transfer flexo printing technology , Because flexo plate making process is relatively simplified , Use water-based oil , No pollution , Green environmental protection , Now more and more commodity printing rice uses flexible technology .

For example, the packaging cartons of liquid food are basically printed by flexo printing process , But the disadvantages of flexo printing process are obvious , Uneven ink transfer , It can't achieve dot superposition effect well , So it is generally the effect of color block . The printing and uncovering machine used for carton packaging , It also belongs to a simple embossing process .

Flexographic printing was originally a process of printing with molded rubber relief , Because the printing ink originally prepared with aniline dye , So it was once known as aniline printing . The earliest aniline printing press was in 1890 It was first created by the British , Originally used for paper bag printing , It was later promoted for food 、 Medicine and other packaging and printing . Because aniline dye is toxic , Prohibited by who , The formulation of the ink used has long changed , People then proposed to change the name .

1952 The year is on the 14 At the th Annual Packaging Conference, it was decided to change its name to flexography.“flexo” Has the meaning of being flexible , Flexographic printing . Flexographic plates are photosensitive polymers , Such as DuPont's Saili version , The main component is synthetic rubber , Develop with organic solvents . And alcohol solubility 、 Alkali soluble and water-soluble flexible printing plates . Because the plate 、 Improvement of ink and printing equipment , The quality of flexographic printing has been greatly improved , Has been applied to newspapers 、 Book printing , It is a very promising process in letterpress printing .

Relief offset printing is a thin relief made of photosensitive polymers ( It's usually 0.25 Mm or so ), Like offset printing , The ink on the printing plate is first transferred to the blanket cylinder , Then transfer to the printing sheet , Therefore, it is also called indirect embossing . Because the printing plate does not need to be wetted , It is also called dry offset printing . It has the advantages of embossing ( The ink is thick ), And avoid the weakness of offset printing ( Side effects caused by wetting solution ). But the cost of plate making is high , The rubber blanket is easy to appear concave and shriveled marks due to the long-term embossing of the relief type layout , Short service life ..

   The difference with gravure printing

There are many differences between the image part and the non image part , Contrary to letterpress , That is, the inked part of the printing plate has an obvious depression under the plate , The non - image part is glossy and smooth . When printing, you need to roll the ink on the plate first , Then the ink naturally falls into the impression part of the depression , Then wipe the ink adhered to the surface ( Of course, the sunken image ink will not be erased ). After putting on the paper, use a larger pressure to imprint the sunken image ink on the paper . Anyone who uses this printing method is called “ gravure ”.

Printing features

advantage ： The expressiveness of the ink is about 90%, Rich colors . Strong color reproduction . Strong layout tolerance . The printing quantity is huge . A wide range of paper applications , Materials other than paper can also be printed .

defect ： Plate making is expensive , Printing is also expensive , Plate making is more complicated , A few copies are not suitable for .

Range of application

Engraving intaglio printing , Because its lines are exquisite , And not easy to fake , Therefore, they are all used in the printing of securities , Such as money 、 Stocks 、 Gift certificate 、 Stamps and certificates of commercial reputation or stationery, etc . Because of its high cost of plate making and printing , So general printed matter , Few adopters . As for gravure, the process of making plate is more complicated , And its cost is also more expensive , Therefore, it is not suitable for printing a few copies , It is generally used in a large number of printed materials , Such as color magazines and popular building materials printing, etc , Are extremely suitable . Gravure printing is a high-speed rotary printing machine , Not only the speed is fast, but also the ink film is much thicker than relief or lithography .

quality requirement

Product quality refers to the characteristics that a product is suitable for a certain purpose and can meet certain needs of people . Printed matter has many uses , Different varieties , Printing methods vary , According to the process and equipment of letterpress printing , The quality of printed matter shall meet the following requirements ：

Dimensional requirements

The allowable error of the format size of fine products is 0.5mm, The general product is 1.0mm.

pressure 、 Ink

The pressure of the printing format 、 The ink is even . Text imprint , Fine products are clear and complete , General products have no obvious missing strokes .

Requirements for the evenness of printed pages

Of fine products The format is uniform The uniformity should be greater than 15/16, The width uniformity of general products shall be greater than 14/16.

Sleeve section

In printed pages , Each page is 、 Reverse overprint is accurate , The overprint error of fine products is less than 1.5mm, General products are less than 2.5mm.

appearance

Fine products , The printed pages are neat , No paste 、 Nail shadow 、 Dirty marks 、 No missing strokes . General products , The printed pages are neat 、 No obvious paste 、 Nail mark 、 Dirty marks 、 No obvious missing strokes .