|
November 2010 —
The gravure printing process is known for its wide tonal range, ability to print on a broad range of substrates, and its high colour stability. For added value work, in-line operations are well suited to gravure. Cold seal, PvdC, varnishing, laminating and sheeting can all be done on-press at high speed. These, and its many other qualities account for gravure’s well-deserved reputation for being perhaps the best printing method available.
Process overview
Gravure is an itaglio printing process. The image carrier has the image etched below the surface of the non-image area. On the gravure image carrier (the engraved cylinder), the image is screened, creating thousands of tiny cells. The substrate is bought into contact with the image carrier with the aid of an impression roller, and at the point of contact, ink is drawn out of the cells and onto the substrate by capillary action.
During printing, the engraved cylinder is immersed in the ink. As the cylinder rotates, ink fills the cells and covers the surface of the cylinder. This surface is wiped with a doctor blade, leaving the non-image area clean while the ink remains within the recessed cells.
Much has been done by the various manufacturing sectors to address the perceived drawbacks of the process, namely that its only suitable for long runs, and that its too costly compared with processes such as flexo (the cost and time involved in engraving cylinders supposedly makes it economical only for long runs), and that it requires a dedicated prepress system.
For example, with all the innovations that have taken place in digital prepress and computer-to-plate, printers and converters might be taken aback to learn that gravure printers were the amongst the first to pioneer a total digital workflow to generate production cylinders. Filmless workflows were integrated into both page and forme production and now most gravure cylinders are made by digital technology. A digital direct-to-gravure system engraves quickly allowing for rapid turnarounds. For packaging applications links to CAD systems are now available, allowing for the import of positioning and layout data to aid in the creation of the cylinder layout.
Opinions vary but many printers and converters believe that if the design is to be run over time then gravure actually out strips flexo for cost effectiveness. The same set of gravure cylinders will last for the life of the design, giving optimum production performance.
Press manufacturers have also worked hard to reduce changeover times, to make the process more suitable for shorter runs, and in general, to make gravure a more versatile medium. However, its not just the press manufacturers that have been busy; pre-press colour communication specialists such as RK Print Coat Instruments Ltd have recently unveiled new compact proofing technology that can seamlessly be integrated in with gravure production workflows.
The new GP100 is a compact bench top device for the production of high quality proofs using gravure inks of press viscosity. With the GP100 any flexible substrate can be printed; it incorporates a microprocessor controlled servo drive and offers a high degree of controllability with variable printing speeds of between 1 to 100 metres per minute.
Tom Kerchiss of RK Print Coat Instruments says: “ The GP100 is ideal for research and development, computer colour matching and for the production of presentation samples. Both producers of gravure inks and the user of such inks will find the GP100 invaluable when used for quality control purposes.”
In operation ink is transferred from an electronically engraved printing plate directly onto the substrate, which is attached to a rubber impression roller. Doctor blade and roller adjustments are made pneumatically allowing for ease of repeatable settings to be made as and when required.
The GP100 has been designed for ease of use and easy clean; the device uses the same electronically engraved printing plates as used in the industry acclaimed RK Print Coat Instruments K Printing Proofer and are manufactured in exactly the same way as production cylinders.
For further information email sales@rkprint.com, www.rkprint.com
Source: RK Print Press Release
|
