Image Quality Gravure Printing Technology
If you are new to flexible packaging, we can guide you through every stage of the packaging process from the very moment you make contact to the moment you receive a pallet of finished goods.
Please see a quick overview of the gravure printing process that is used at SLS Packaging Solutions to produce millions of gravure printed packaging every year:
What is Gravure Print?
Rotogravure printing or just simply gravure printing is a type of intaglio printing process which uses a rotary printing press. It involves engraving an image onto a copper plated steel cylinder base.
The first step is to create a cylinder with an engraved image for each colour that makes up the design. The engraving process will create on the cylinder surface the cells that will contain the ink in order to transfer it to the substrate (film or paper). Since the amount of ink contained in the cells corresponds to different colour intensities on the substrate, the dimensions of the cells must be carefully set: deeper cells will produce more intensive colours whereas less deep cells will produce less intensive ones.
A rotogravure printing press has one printing unit for each colour, typically CMYK or cyan, magenta, yellow and key (printing terminology for black), but the number of units varies depending on what colours are required to produce the final image. There are five basic components in each colour unit: an engraved cylinder (AKA “Gravure cylinder”) whose circumference can differ according to the layout of the job; an ink fountain or reservoir; a doctor blade; an impression roller; a dryer.
How does it work?
The ink is applied directly to the cylinder and from the cylinder it is transferred to the substrate.
While the press is in operation, the engraved cylinder is partially immersed in the ink fountain, filling the recessed cells.
As the cylinder rotates, it draws ink out of the fountain with it. Acting as a squeegee, the doctor blade scrapes the cylinder before it makes contact with the substrate, removing excess ink from the non-printing (non-recessed) areas and leaving in the cells the right amount of ink required: this tool is located quite close to the substrate so that the ink left in the cells does not have enough time to dry.
Next, the substrate gets sandwiched between the impression roller and the gravure cylinder: this is where the ink gets transferred from the recessed cells to the substrate. The purpose of the impression roller is to apply force, pressing the substrate onto the gravure cylinder, ensuring even and maximum coverage of the ink.
The capillary action of the substrate and the pressure from impression rollers force the ink out of the cell cavity and transfer it to the substrate. Then the substrate goes through a dryer because it must be completely dry before going through the next colour unit and absorbing another coat of ink.