Gravure printing involves the usage of engraved cylinders as image carriers that are printed on surfaces using the rotary printing press. It is a kind of ‘Intaglio printing’ process, which involves the usage of a printing technique in which the image carrier is usually sunken rather than other printing methods in which the image carrier stands-out or is embossed over the surface.
It is a printing process with very few parameters to control, making it simple to understand and use for large scale production as per the desired output. To know more about ‘what is gravure printing?’ and ‘how is it done?’ go through the entire article.
It was invented in the nineteenth – century but is still used for several applications like:
Commercial printing of newspapers
Gravure printing and its unique process are explained in detail in the upcoming parts of the article. You can easily understand the entire working of gravure printing, its uses, and the machines involved in making this possible!
Gravure Printing Machine
The gravure print is achieved mainly using cylinders that carry the ink to the substrates such as paper, cloth, etc. To understand the printing process, first, we must know about the components involved in the gravure printing machine:
An ink fountain
A doctor blade assembly
The cylinder that would be used to carry ink and print images is engraved according to the required final image.
The engraving process is very important as it creates the cells that would hold the ink. Based on the ink stored in each cell, the intensity of the final image would vary hence the dimensions such as depth of the cells must be carefully calculated.
Larger cells would produce high-intensity colors whereas smaller ones will produce color with low intensity.
The different methods involved in the engraving are:
Lateral hard dot
In each of these methods, the cell depth and size variability are different. Hence, one must choose it accordingly.
The cylinder is usually made of steel, which is coated by copper plating. Other materials like – Ceramics can also be used.
The etching of the cylinder can be done in different ways, such as:
In chemical etching, to protect non-image areas, the cylinder is first protected with a resist. This ensures that chemical etching is done only in the image area.
The cylinder dimension varies from being as small as 3 inches to large cylinders of 40 inches diameter.
The doctor blade is used in various types of printing to remove the excess ink from the non-engraved parts of the etched cylinder.
It is also used in Flexo printing and Pad printing techniques.
It ensures the removal of unwanted ink-staining and proper image formation during the gravure printing.
Gravure inks and resins
Solvent-based inks are mainly used for gravure printing but with the rise in need for environment-friendly alternatives, water-based inks are used nowadays.
Resins help in adding gloss to the gravure print, hold, retain the ink, and allow smooth flow.
Impression roller and dryer
The impression roller is used to produce pressure such that the ink adheres to the substrate uniformly.
The dryer systems are used according to the size of the substrate for quick drying and effective color adherence such that it would be ready for the next color application.
The gravure printing machine also consists of a coating tray or pan, knife, applicator pipe working on the gravure roll.
The most common gravure cell patterns are:
Check out one such example of commercial Gravure printing or Rotogravure printing machine here.
Gravure printing process
The gravure printing involves the usage of one printing unit for each color.
The process begins with the etched cylinder being immersed into the ink tray to load ink into the cells with different depths.
The cylinder rotates during the filling of cells, causing excess ink to stick to its surface.
This excess ink that is not necessary for the printing of an image is scrapped from the cylinder by the doctor blade.
Now the substrate or paper to be printed is sent between the engraved Gravure roller and the impression roller. The impression roller is used to ensure proper contact of ink with the substrate by exerting the optimum amount of force on it.
The ink gets transferred quickly to the dry surface of the substrate due to surface tension.
After printing, the substrate is conveyed to the dryer for complete drying as it has to then move for imposing of the next color.
Features and advantages of Gravure Printing
This type of printing is mainly used for fine-art printing as the depth of ink and its intensity is better than other printers.
High-quality printing is possible with this technique.
The cylinders run over a longer period with a low maintenance requirement.
As mass production is possible, the per-unit cost is reduced.
As this involves direct inking of the image over a substrate, the image rendering is better.
The printing is continuous hence no seams or finish lines are visible making the print neat for making wall-papers, gift wrappers, etc.
One cylinder set can run up to 2-3 million prints.
The production speed is high, ranging from printing of 3000-3300 feet per minute.
It is best suitable for printing packaging materials as long runs are possible.
Disadvantages of Gravure Printing
As every coin has two faces, everything or process has advantages as well as certain disadvantages.
Some of the difficulties in Gravure printing are:
The initial cost or start-up costs are high. So to make a profit, thousands of copies must be printed.
The image clarity is not so clear as in offset printers.
The cylinder preparation requires long time durations for exact engraving and designing.
Gravure printing is one of the earliest found printing techniques that has its uniqueness and specialty. The overall information and facts about Gravure printing have been covered in this article. Hope it was useful and has left a nice print on your creative minds!