- September 01, 2009, By David Argent Contributing Editor
Last month's column addressed some changes in thinking regarding gravure's declining market share in package printing. One technology that can help the gravure process is the use of lightweight sleeves in place of steel cylinders. A typical steel base cylinder that is 4 ft long with a 10 in. dia weighs several hundred pounds. Maneuvering these cylinders in and out of the press and in and out of storage is cumbersome to say the least. Transporting them to and from the engraver involves special problems because of the weight and delicate surface. Special containers must be used.
All in all, this routine seems to belong to another age, especially in the context of flexo competition with shorter runs and rapid turnaround times. Could lightweight cylinder sleeves be the answer for gravure? In new gravure presses, sleeves can be removed through the side of the press much like modern flexo presses.
Benefits of Gravure Sleeves
The base gravure sleeve is comprised of 178 microns of nickel and 35 microns of copper. An engraveable copper layer 140 microns thick is added by the sleeve manufacturer or the engraver. After engraving, a chrome flash layer about 12 microns thick is added by the engraver. This gives a total thickness of 355 microns or 0.014 in. They are mounted and demounted easily from an air cylinder just as flexo sleeves are.
Technical benefits of sleeves include quick changes that support short-run economics, with 20%-30% less downtime. Jobs can be moved easily from press to press and to other locations. Engraving times are reduced, since no old images need to be removed, and there is no waiting for bases to be shipped. In most other respects, sleeves perform like traditional cylinders in both engraving and press operations. Sleeves should be given extra consideration any time a new repeat is added. The capital investment for new sets of gravure bases can be reduced by purchasing only a few air cylinders in conjunction with sets of sleeves.
Sleeves offer ergonomic benefits as well. The weight of a sleeve is 10-15 lb compared to 500 lb for a conventional cylinder. This has a dramatic effect on shipping, storage, retrieval, and press setup in terms of speed, cost, and safety. An operator easily can move eight sleeves on a light duty trolley from storage to the press. Innovative storage solutions are available as a result of their low mass. Lightweight shipping cartons can be used for storage and can be stacked without use of racks.
Frequently Asked Questions
- Does the edge of the sleeve impact the doctor blade? The edge of the sleeve is no problem to doctor blade systems on a gravure press, whether it is oscillating or stationary.
- Can a sleeve be de-chromed and re-chromed? Yes, most gravure sleeves can be de-chromed and re-chromed with no issues. A limiting factor is the condition of the sleeve, i.e., it must be handled in a way to prevent damage.
- Can a sleeve be re-imaged multiple times? Sleeves can be re-imaged. It is up to the engraving facility to determine if it is possible and at what cost, as not every sleeve is worth re-imaging. The condition of the sleeve also comes into play here.
- Can a sleeve be repaired if the image is damaged? In most cases, minor damages to the surface can be repaired. If the method of repair requires deep copper removal and replacement, then sleeves are not as repair-friendly. Minor scratches and surface marks can be removed in the same fashion as that of a gravure cylinder.
- Do I need to buy all new cylinders to use sleeves, or can my existing cylinders be modified? In many cases, existing cylinders can be modified to accept a gravure sleeve. It is recommended to use only the best base because once it is modified, it will stay in that condition, and it will stay in your location.
- Can my current press be adapted for quick changeover for sleeves? Many existing presses have been modified to allow the sleeves to be changed on the press without removing the base cylinder. This may or may not be possible based on the individual brand of press you have.
Many thousand sleeves are in day-to-day use but represent a small part of the potential market. Let's look at gravure sleeves as a possible analog of photopolymer plates. In flexo printing, the almost complete change to photopolymer plates could not have happened without supporting collaborative changes in presses, anilox rolls, inking systems, and prepress workflow.
Slow adoption of gravure sleeves could be a result of a lack of supporting infrastructure, but the opportunity waits — for a while.
Editor's Note | Some information in this column was supplied by Stork Prints America, Charlotte, NC.
Process improvement expert David Argent has 30+ years of experience in process analysis with particular emphasis on ink and coating design and performance. Contact him at 314-409-4304; email@example.com.