When you purchase packaging bags,like stand up pouches,flat bottom bags,and other food packaging bags,you will often see the packaging bags suppliers mentioned about cylinders,so what are cylinders and how it works in the printing?
When you purchase mass packaging bags,to save cost,the packaging bags supplier will use rotogravure printing,and in rotogravure printing, cylinders are typically made of steel or copper and play a central role in the transfer of ink onto the substrate.
In rotogravure printing, multiple cylinders are used, each representing a different color or part of the image being printed. The number of cylinders used depends on the complexity and color requirements of the print job.
Each cylinder is engraved with a specific image or pattern that needs to be printed. The engraving process creates small cells or indentations on the surface of the cylinder. These cells hold the ink that will be transferred onto the substrate.
Here's a step-by-step explanation of how the cylinder works in rotogravure printing:
Cylinder Preparation: The printing cylinder is typically made of steel or copper. It is initially polished to achieve a smooth surface.
Engraving: The cylinder goes through an engraving process, where the image or pattern to be printed is etched onto its surface. This is usually done using a laser or an electromechanical engraving system. The engraved pattern consists of numerous small cells or depressions of varying depths.
Ink Application: The cylinder is partially immersed in an ink pan, and an ink applicator, such as a doctor blade, scrapes off the excess ink from the cylinder's surface, leaving ink only within the engraved cells.
Doctor Blade: A doctor blade is a thin metal strip that contacts the cylinder's surface. It helps to control the amount of ink within the cells by removing the excess ink and leaving behind a uniform layer of ink in the cells.
Substrate Contact: As the cylinder rotates, the inked cells come into contact with the substrate, which can be paper, plastic, or any other printable material.
Pressure and Transfer: A rubber-covered impression roller, also known as a pressure roller, applies pressure to the substrate against the rotating cylinder. The pressure causes the ink in the cells to be transferred from the cylinder to the substrate.
Drying: After the ink is transferred, the substrate passes through a drying system, which can involve hot air, infrared radiation, or other methods, to evaporate the solvent and fix the ink onto the substrate.
Repeat Process: The cylinder continues to rotate, and the substrate is fed through the printing press for successive impressions, allowing for multi-color or continuous pattern printing.
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By repeating these steps for each color or pattern, rotogravure printing achieves high-quality and consistent results. The cylinder's engraved cells hold the ink and transfer it to the substrate through the pressure exerted during contact with the substrate, resulting in the desired image or pattern being reproduced on the printed material.
The cylinder quantity is about how many color you used in your design,each color,each cylinder,so the cylinder charge is based on how many colors you use in your design.Normally the cylinder charge is one time charge,and will not charge again for re-orders as long as the artwork is not changed.
The rotogravure process is a direct transfer method for printing onto wood-pulp fiber based, synthetic, or laminated substrates, including:
The modern day rotogravure printing press uses a printing cylinder which has been laser engraved with minute cells capable of retaining ink, the size and pattern of which reflect the required image. These cells are forced to transfer their ink directly onto the substrate by a combination of pressure and capillary action, so producing the printed image.
The process, also commonly called gravure printing, is used in the manufacturing of food and non-food packaging, as well as labels, wall coverings, transfer printing, and has a variety of further applications in the security printing, industrial, and tobacco segments of industry.
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.
A formidable innovator, focused on creating value for its clients, products from the BOBST Rotomec range have established an unparalleled reputation in gravure printing press technology, setting the standard for state-of-the-art, ultra productive, and user-friendly rotogravure printing machines.
The high efficiency features and waste reduction performance of Rotomec gravure printing presses are enhanced by electronic line shaft and Registron® print register technology which slash production times and cut material wastage by unprecedented amounts.
As an equally impressive innovator, BOBST, through its LEMANIC® range of gravure printing presses, sets the standard for web-fed gravure printing in demanding segments such as tobacco packaging. Printing on paper or carton board poses specific challenges to the gravure process, but the technological advancement, ease of use, fast make-ready, and waste minimization features of BOBST presses have made them a worldwide reference amongst end users.
Through its specialized rotogravure Kochsiek printing machines, BOBST serves the markets for decorative printing and liquid packaging. Precise design, high manufacturing standards, and state-of-the-art computer based control ensure that BOBST rotogravure printing presses deliver the highest production quality, exceptional reliability, and long-lasting value.
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