There has been a lot of debate regarding sleeves and their value to flexo printers. The purpose of a sleeve system is to allow a converter to utilize their press more efficiently, reduce cost and enhance print quality, but there are so many types of sleeves to choose from. The traditional composite or nickel sleeve, cushion print enhancing sleeves and build up sleeves. They each have their own distinct advantages:
- Light weight and easy to handle
- They provide the printer greater flexibility when scheduling production runs
- Reduces plate making and mounting costs
- Decreases change over times
- Reduced plate cylinder inventory
- Cushion sleeves eliminate stickyback variables and breakdown of stickyback cells
- Consistent quality from run to run
- Better balance for faster press speeds
These advantages are great but printers are faced with the same old challenges with mounting on mandrels. This includes plate lift caused by water or solvents penetrating under the plate or from the pounding the lead edge of the plate takes when it comes in contact with the impression
cylinder. This pounding can also cause excessive wear. Registration and mounting cause many other problems. Skilled personnel, mounting equipment maintenance , materials and waste from mounting and demounting jobs can be very expensive and time consuming.
A continuous polymer printing sleeve eliminates all of these challenges and combines all the advantages of a sleeve with comparable gravure and offset print quality. One reason is in the advances made in computer to plate technology (CTP). A continuous printing sleeve digitally imaged in the round (ITR) fully utilizes a digital workflow with platesetter precision. Printers are able to come to color and match a digital proof faster and more accurately with digitally imaged sleeves. Imaging in the round reduces cutback curves and produces a sharper dot. It also replaces the need for film with a integral mask for plate exposure. This allows for the smallest dot to be printed. There are no film costs and associated exposure variables as seen in a conventional plate making method. The process opens reverse copy and sharpens line work with greater plate uniformity. Another advantage can be seen with combination plates. They can print good solids without jeopardizing screens. This allows printing decks to be free for varnishes or the ability to print more colors.
A continuous printing sleeve also takes on the same characteristics of a gravure cylinder. Sleeves are easily mounted and demounted without damage for a repeatable process with perfect registration every time. There is never a plate break or gap. The digitally imaged dot imaged on a cushion sleeve gives greater latitude on press so that it can withstand over impression without filling in reverses or tonal shifts. Recent fingerprint tests have shown up to .010-.015” of impression before major dot gain, slur or tonal shifts can be seen. The extra impression can also contribute to cleaner plates. This can be extremely valuable for different press operators or production shifts to duplicate print quality from start to finish. This superior quality adds to the competitive edge and is cost effective when production time, make ready, plate, film and substrate costs are analyzed completely.
The improved process has the capability to provide extremely quick and cost efficient turn around from end user to printer. For instance, a converter may have a need to react quickly to a promotion or event such as the Superbowl. Their client may want to have a promotion or special packaging with the Superbowl MVP on the shelf within 12-24 hours. This obviously requires preliminary prepress steps (to a design or multiple designs) prior to the conclusion of the game, but the prepress shop can image and produce continuous printing sleeves ready for the converter to print immediately on delivery. I realize this is an extreme example, but it’s the reality of the markets demands.
Digitally imaged continuous photopolymer sleeves are the future of flexography with growing interest. Flexo printers need to examine and adjust their process to achieve greater productivity and quality. The success of this technology is available and the benefits are untouchable.