Weyerhaeuser increased pre-press production by 100 percent, cut downtime between runs, reduced pre-press waste and improved safety with a new digital vision plate mounter/proofer system.
Flexographic printing has long been considered a low-quality printing system, but a mainstay for the printing of packaging containers, including flexible packages like food bags, shopping bags and self-adhesive labels. Technical developments over the past few decades in the flexo printing process have improved print quality, by enhancing the ability to reproduce highlight tonal values - working around the very high dot gain associated with flexo printing, and by making accessible four-plus-color applications. But the systems for the mounting and calibration of flexographic plates onto printing cylinders have not evolved enough technologically to provide for quick and highly accurate mounting of the flexible printing plates.
Plate Mounting Bottleneck
Passing the Field Test
A Better Mounting SolutionThe Leader system is a state-of-the-art vision system capable of mounting almost every type of flexographic printing plate. The computer and its software take electronic data from the art department and send it directly to the mounter/proofer computer to mount the plate with only two clicks from the mounter operator. It utilizes a dual camera system, with a large view camera that locates microdots or reference points on a pre-press table holding the plate to be mounted. <br><br> The narrow view camera then magnifies the microdots 70 times and pinpoints the exact center-point for accurate registration. The plate is then positioned, and the system brings the plate up against the press cylinder with a pressure roller and applies the plate exactly to a corresponding micro-dot position on the press. Operator variations are removed because this system does not require the operator to position the microdots. <br><br> Unusual with plate mounting and proofing systems, the Leader machine ensures good prints from the first revolution of the print cylinder. Excessive plate handling, which causes damaged plates, is eliminated, as is misalignment of plates due to parallax from positioning of the human eye. Vacuum grooves secure the plate to the pre-press work station, eliminating punch holes.
Tighter Plate Registration & Production Downtime ReducedThe Leader Vision system is so tight on its registration that Weyerhaeuser has uncovered tolerance aberrations in its printing plates that it did not realize existed while using its prior manual plate mounting method.
“We are working with plates that are 50-inches x 80-inches in size, large sheets of material,” says Matthews. “It is not unreasonable to think that there was going to be some tolerance variations in the plate making process. The plate makers can introduce variation in the way the plates are made: the timing of the exposure, the timing of the washout, the timing between the washout and the drying, etc. If these sequences vary at all in the plate manufacturing process, then one plate will be longer or shorter than the other.
“These variations affect the registration on press, which are not always evident in traditional mounting systems. The Leader equipment showed up the aberrations immediately, and allowed us to compensate for the deviations accordingly. It really brought it to our attention how much unknown variance was occurring on our prior system,” he says.
The amount of time it takes to get a job on press is typically the same whether it is a one-roll job or a twenty-roll job. Weyerhaeuser runs a lot of smaller orders of one and two rolls. Instead of spending up to four hours mounting plates for a new one- or two-roll job like before - and running another job as a fill while the next job is being set up - they simply pull the cylinders out of the press, go back to the mounter and have the cylinders back and ready to go back on the press in a fraction of the time. Down-time has been greatly eliminated with the Leader system.