Flexo Plate Sleeves
February 2005
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The world of flexo plating moves from flat to round.
THOUGH IT MIGHT be tough to remember, it was only a few years ago that computer-to-plate (CTP) for flexo was considered a speculative technology. Today, with many hundreds of digital flexo imaging machines installed around the world, it's fair to say that flexo CTP technology is here to stay. And, as is typical of our ever-changing industry, when one technology matures, another is bound to emerge.
The new kid on the flexo platemaking block is in-the-round, or ITR imaging. ITR differs from standard digital flexo imaging in that the photopolymer plate material is actually imaged and processed directly on a sleeve that will subsequently be loaded onto the press versus mounting a flat plate to the printing cylinder. The advantages of ITR are numerous but the logistical and cost factors can be considerable.
One thing moving adoption along is the prevalence of the gearless CI and inline presses that require sleeves or are sleeve compatible. Sleeve systems reduce press downtime, and at today's hourly rates, that's significant. While one job is on press, the next set of sleeves can be ready and waiting. Sleeves may reduce inventory and tooling costs as well. Using sleeves with varying thickness, a printer might only have to buy nine cylinders to outfit an 8-color press instead of 16—eight to fill the press, and one to use as a base for mounting plates on a second set of sleeves.
Sleeves have other inherent pressroom advantages, too, such as savings on sticky back. Plus, since the plates are stored on the sleeve, printers don't run the risk of stretching or ripping them when they're removed from print cylinders.
From a quality standpoint, ITR imaging offers an exponential improvement over flat plate imaging. The distortion factors and skew errors associated with imaging a flat surface and then mounting that flat plate around a cylinder are completely eliminated. Color-to-color registration is achieved far more quickly because all sleeves are imaged at the same origination point and orientation.
One of the quality challenges with ITR imaging, however, has been the problem of edge cure. It is extremely difficult by conventional methods to mask the outermost edges of the sleeve polymer to prevent it from being exposed by the light source. This can cause the edges of the plate sleeve to retain an undesirable relief that will transfer ink to the substrate. Currently, platemakers use a variety of workarounds to mask the plate edges, such as painting, airbrushing, and taping on a UV blocking agent. These methods work to varying degrees of success, but hand-masking is often time-consuming and is by no means an exact science.
THOUGH IT MIGHT be tough to remember, it was only a few years ago that computer-to-plate (CTP) for flexo was considered a speculative technology. Today, with many hundreds of digital flexo imaging machines installed around the world, it's fair to say that flexo CTP technology is here to stay. And, as is typical of our ever-changing industry, when one technology matures, another is bound to emerge.
The new kid on the flexo platemaking block is in-the-round, or ITR imaging. ITR differs from standard digital flexo imaging in that the photopolymer plate material is actually imaged and processed directly on a sleeve that will subsequently be loaded onto the press versus mounting a flat plate to the printing cylinder. The advantages of ITR are numerous but the logistical and cost factors can be considerable.
One thing moving adoption along is the prevalence of the gearless CI and inline presses that require sleeves or are sleeve compatible. Sleeve systems reduce press downtime, and at today's hourly rates, that's significant. While one job is on press, the next set of sleeves can be ready and waiting. Sleeves may reduce inventory and tooling costs as well. Using sleeves with varying thickness, a printer might only have to buy nine cylinders to outfit an 8-color press instead of 16—eight to fill the press, and one to use as a base for mounting plates on a second set of sleeves.
Sleeves have other inherent pressroom advantages, too, such as savings on sticky back. Plus, since the plates are stored on the sleeve, printers don't run the risk of stretching or ripping them when they're removed from print cylinders.
From a quality standpoint, ITR imaging offers an exponential improvement over flat plate imaging. The distortion factors and skew errors associated with imaging a flat surface and then mounting that flat plate around a cylinder are completely eliminated. Color-to-color registration is achieved far more quickly because all sleeves are imaged at the same origination point and orientation.
One of the quality challenges with ITR imaging, however, has been the problem of edge cure. It is extremely difficult by conventional methods to mask the outermost edges of the sleeve polymer to prevent it from being exposed by the light source. This can cause the edges of the plate sleeve to retain an undesirable relief that will transfer ink to the substrate. Currently, platemakers use a variety of workarounds to mask the plate edges, such as painting, airbrushing, and taping on a UV blocking agent. These methods work to varying degrees of success, but hand-masking is often time-consuming and is by no means an exact science.
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