Rotogravure Printing Process & Advantages - LinkedIn

Rotogravure printing is a high-quality and high-speed printing technique widely used in the flexible packaging industry. This method is especially suitable for large volume production due to its efficiency and the consistent quality it delivers. Here’s a detailed overview of the rotogravure printing process for flexible packaging:

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Rotogravure Printing Process

1.      Cylinder Preparation:

·         Engraving: The process begins with preparing the printing cylinder, typically made of steel or aluminium. The image to be printed is engraved onto the cylinder surface, either mechanically using a diamond stylus or chemically using acid etching. Modern techniques often use laser engraving for higher precision.

·         Chroming: The engraved cylinder is then chrome-plated to increase its durability and resistance to wear, ensuring a longer lifespan during the printing process.

2.      Ink Application:

·         Inking Unit: The cylinder is partially immersed in a pan of liquid ink. The engraved cells on the cylinder pick up the ink as it rotates.

·         Doctor Blade: A doctor blade scrapes excess ink off the surface of the cylinder, leaving ink only in the engraved cells.

3.      Printing:

·         Substrate Contact: The substrate, which can be various types of flexible materials such as plastic films (e.g., PET, BOPP), foil, or paper, is pressed against the inked cylinder by an impression roller. The pressure from the roller helps transfer the ink from the engraved cells onto the substrate.

·         Drying: The printed substrate is passed through a drying oven to evaporate the solvents from the ink, ensuring it adheres properly and dries quickly.

4.      Rewinding:

·         The printed substrate is then rewound into rolls for further processing, such as lamination, cutting, or conversion into the final packaging product.

Advantages of Rotogravure Printing for Flexible Packaging

• High Quality: Produces high-resolution images with excellent colour consistency and rich, vibrant tones.
• Speed: Capable of very high-speed printing, making it suitable for long print runs and large-volume production.
• Durability: The chrome-plated cylinders are highly durable, making them suitable for printing millions of impressions without significant wear.
• Versatility: Can print on a wide range of substrates, including thin and flexible materials.
• Detail: Excellent at printing fine details and gradients due to the precision of the engraving process.

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Applications in Flexible Packaging

• Food Packaging: Often used for snack bags, pouches, wrappers, and other food-related flexible packaging due to its ability to produce high-quality images that are attractive and informative.
• Pharmaceutical Packaging: Ensures clarity and precision in printing critical information on pharmaceutical pouches and blister packs.
• Consumer Goods: Used for packaging various consumer goods, including personal care products, detergents, and more, where high-quality and appealing packaging is crucial.

Challenges and Considerations

• Cost: Initial setup costs are high due to the expense of cylinder preparation and engraving. This makes it less suitable for short print runs.
• Environmental Impact: The use of solvents in inks and the need for chrome plating can have environmental implications, although advancements in water-based inks and alternative plating methods are being developed.

Technological Advancements

• Digital Engraving: Improved precision in cylinder engraving using digital techniques, enhancing print quality.
• Eco-friendly Inks: Development of eco-friendly and sustainable inks to reduce environmental impact.
• Automation: Increased automation in the printing process for better efficiency and reduced human error.

What is gravure printing and how does it work?

Gravure printing is a highly effective printing technique that is particularly suitable for long runs in flexible packaging. Its direct transfer approach of transferring the design from the cylinder to the substrate allows for exceptional print quality, even at very high production speeds. This makes it the preferred choice for high-volume printing of flexible packaging, ensuring high productivity and sharp, detailed design reproduction on every print.

How does the gravure printing process work?

The gravure printing process consists of several stages, including the preparation of the printing cylinder, the ink setting of the ink, the transfer of the ink to the substrate and the drying of the ink. Below is a detailed description of each stage of the process:

1. Preparation of the printing cylinder: The printing cylinder used in gravure printing is made of steel or copper and is engraved with a series of cells or holes representing the areas of the image to be printed. These cells are created by chemical or mechanical processes, and their shape and size determine the amount of ink that will be transferred to the substrate during printing.
2. Ink setting: At this stage, once the ink has been set to the correct viscosity, it impregnates the bas-relief engraved cylinder. Excess ink is removed from the cylinder by using a steel key with a bevelled profile or lamella.
3. Transfer of the ink to the substrate: During printing, the printing cylinder is brought into contact with the substrate, be it paper, cardboard, plastic or other material, and the ink is transferred from the cells of the cylinder to the substrate by the pressure of the rubber roller. The ink flows by capillary action from the cells to the substrate contact areas, creating the final image with high quality and fine detail.
4. Drying the ink: Once the ink has been transferred to the substrate, it needs to be dried before continuing to the next step of the process. This can be done by applying heat, combined with an air flow, so that the evaporation of solvents or water is accelerated, depending on the type of ink used and the substrate.

Rotogravure Applications

Gravure printing is used in a wide range of applications, especially in the production of flexible packaging, labels, postage stamps, banknotes and board liners. Due to its high quality and capacity rotogravure is also used in the printing of cardboard liners for food and pharmaceutical products, as it offers excellent resistance to moisture and abrasion, protecting the inks with appropriate coatings.

5 Advantages of Gravure Printing

The rotogravure printing system offers several advantages, among which are the following:

1. High print quality: The printing cylinders used in rotogravure have a long service life, which reduces production costs in the long run.
2. High printing quality: The printing cylinders used in gravure printing have a long service life, which reduces production costs in the long term.
3. High print quality: Gravure can be used on a wide variety of substrates, including paper, cardboard, plastic and metals, making it suitable for a wide range of applications.
4. High print quality: The ink used in gravure printing offers excellent resistance to moisture and abrasion, making it ideal for printing products that require durability and resistance in harsh environments. The resistance can be reinforced with varnishes.
5. High print quality: Rotogravure allows the incorporation of security features such as watermarks, microtext and holograms, making it a popular choice for printing products that require authenticity and security.

Gravure Cylinder Maintenance

To ensure optimum performance and long life of the rotogravure cylinder, it is essential to carry out proper maintenance. At Ibeslab we specialise in the supply of products for daily and periodic cylinder cleaning. Water and solvent based cleaners for the dilution and removal of fresh ink used in the printing process.

Our products are ideal for manual cleaning or cleaning via the printer’s circuits.

In addition, we offer concentrated water-soluble formulations to adjust the mix for in-plant use, minimising transport and stock costs.

For cylinder deep cleaning, we have vigorous products capable of removing ink residues accumulated in the cylinder cells and compatible with solvent or water-based inks, adhesives and coatings based on polyurethane and other resins.

Special brushes and sponges to assist in the application of the products are also available.

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