What is rotogravure printing ？
Gravure printing is to make the entire surface of the printing plate coated with ink, and then use a special scraping mechanism to remove the ink from the blank part of the ink, so that the ink is only deposited in the mesh cavities of the graphic part of the ink, and then under the action of a greater pressure, the ink will be transferred to the surface of the substrate, to obtain the printed matter. Gravure printing is direct printing. The graphic part of the printing plate is concave, and the degree of concavity with the level of the image has different shades, the blank part of the printing plate is raised, and in the same cylinder plane.
The rotogravure process is a direct transfer method for printing onto wood-pulp fiber based, synthetic, or laminated substrates, including:
—Films such as PET, OPP, nylon, and PE,PVC,Cellophane
—Papers
—Carton board
—Aluminum foil
Rotogravure printing process
Rotogravure printing due to the high degree of automation of the printing machine, the quality of the plate is good, and thus the process operation is simpler than lithographic printing, easy to master, the process flow is as follows:
Pre-printing preparation → on the cylinder plate → adjust the color registration → formal printing → post-press processing
Process description
During the gravure printing process the printing cylinder rotates in the ink pan where the engraved cells fill with ink. As the cylinder rotates clear of the ink pan, any excess ink is removed by the doctor blade. Further around, the cylinder is brought into contact with the substrate, which is pressed against it by the rubber covered impression roller.
The pressure of the roller, along with the capillary draw of the substrate, results in the direct transfer of ink from the cells in the printing cylinder to the surface of the substrate. As the printing roller rotates back into the ink pan, the printed area of the substrate proceeds through a dryer and onto the next printing unit, which is normally a different color or may be a varnish or coating.
Precise color to color registration is made possible via automatic side and length register control systems.
For a web-fed printing press, after each color has been printed and any coatings applied, the web is 'rewound' into a finished roll.
Now we focus on the printing process can directly affect the printing quality of one of the most important links - color registration
Nowadays, the vast majority of gravure printing machines will use automatic color registration system for pattern registration, which greatly improves the registration efficiency and printing quality.
On the web gravure printing machine, there is an automatic overprinting device installed. The device consists of a scanning head, a pulse generator, an electronic controller, an adjusting motor, an overprint adjusting roller and so on.
When the overprint mark on the printed sheet through the scanning head, the pulse signal will be transmitted to the electronic controller, if the second color of the overprint mark wrong before or after the first color of the mark, the occurrence of the pulse time will be uneven, so the electronic controller to start regulating the motor, so that the first color and the second color of the overprint between the regulating rollers have a small amount of movement, to eliminate overprinting errors.
In addition, there are also the following factors that can affect the quality and efficiency of printing, but we will have the appropriate solutions
a) The ink is uneven in color
The phenomenon of periodic ink color changes on the printed materials. Methods of elimination include: correcting the roundness of the printing plate cylinder, adjusting the angle and pressure of the squeegee or replacing the squeegee with a new one.
b) Fuzzy and linty prints
Printed image levels and level, paste, the phenomenon of burrs on the edge of the image. Elimination methods include: removing static electricity from the surface of the substrate, adding polar solvents to the ink, appropriately increasing the printing pressure, and adjusting the position of the squeegee and so on.
c) blocked version
Ink drying in the printing plate mesh, or the printing plate mesh hole is filled with paper hair, paper powder phenomenon, called blocking. Elimination methods are: increase the content of solvents in the ink, reduce the speed of ink drying, the use of high surface strength paper printing.
d) Ink spillage
The phenomenon of spots appearing on the field part of the print. Elimination methods include: adding hard ink blending oil, improve the viscosity of the ink. Adjust the angle of the squeegee, increase the printing speed, and replace the deep-cavity printing plate with a shallow-cavity printing plate.
e) Scratch
There are traces of squeegee on the print. Elimination methods are: use clean ink without foreign matter mixed in the printing. Adjust the viscosity, dryness and adhesion of the ink. Use high-quality squeegee, adjust the angle between squeegee and printing plate.
OYANG's design engineers analyzed and optimized the machine structure according to a series of problems in the printing process, and designed the Honor Sereis ELS Rotogravure Printing Machine from the perspective of solving the pain points of the users and the industry.
Rotogravure Process advantages and applications
The process offers the ability to transfer ink consistently, across a wide range of densities, and at high speeds, making it suitable for applications which require high image quality, such as publishing, packaging, labels, security print, and decorative printing.
The durable nature of the printing cylinders used makes gravure printing an ideal process for providing high quality print on very long or regularly repeating runs, delivering cost advantages over other processes.
OYANG expertise and knowledge
A formidable innovator, focused on creating value for its clients, products from the OYANG Rotogravure press making, In just three years OYANG Rotogravure press has built up a good reputation and good name in China, and there are many countries and regions around the world where customer factories have our Honor series electronic shaft rotogravure printing presses, and they run very stably.
An equally impressive innovator, OYANG has set new standards in web-film gravure printing in demanding areas such as flexible packaging with its Honor® series rotogravure presses. Achieving outstanding print results on high-end laminated flexible packaging poses new challenges for the gravure printing process, but the technological advancement, ease of use, fast turnaround time and reduced waste of OYANG presses make them one of the top choices for customers in China and around the world.
