The quality of a flexographic-print job depends, to a large degree, on the care in which prepress preparations are carried out. This includes mounting the plate on the cylinder, checking color registration, and proofing. A common method to mount and align plates involves drawing of a line around the printing cylinder. This line is then aligned by eye with a longitudinal line along the length of the photopolymer or other plate. The plate is then wrapped around the cylinder. While this method is somewhat accurate, it can be extremely time-consuming. Other plate mounting and calibration systems have been devised for flexo printing using manual or semi-manual systems. Each method has proven error-prone in registration.

But recently, a new high-tech, fully-automated, digital system of plate mounting and proofing has become available for use on flexographic-printing equipment. Called the Vision Plate Mounter/Proofer®, manufactured by Leader Engineering-Fabrication, Inc. (www.flexomounting.com), it is said to deliver rapid, precise mounting for both horizontal and vertical alignment, accommodating different sizes of printing plates and cylinders. Selected and tested by Weyerhaeuser's Containerboard and Recycling Div., the Vision Plate has become the system of choice within several of the converter's US flexo-print facilities.

The Weyerhaeuser Containerboard Packaging and Recycling Div. (www.weyerhaeuser.com), one of the company's five operating divisions, produces paper, corrugated boxes and multiwall bags. It also provides a full spectrum of point-of-purchase design, production, packaging and fulfillment services, including some of the world's most sophisticated flexo-printing centers.

“We were looking for increased throughput and improved quality in our mounting area because of the constraints that mounting was having on our printing presses,” says Harry Matthews, superintendent of the Weyerhaeuser preprinted-linerboard plant in Tucker, GA. “We are challenged with shorter lead times, smaller orders and tighter registration, and we felt that the Leader Vision system could address all of these issues. We purchased one of these mounters back in 2005. Initially, we looked at the machine because our Hillsboro sister-plant in Oregon had been using the same machine and had done real well with it.

“Before, it would take one of our mounters about one hour to mount a plate on the print cylinder,” continues Matthews. “With the Leader machine, they can do it in about 10 minutes. From a quality standpoint, one of our biggest downtime problems was sending jobs to the printing press that were not in registration, or were not quite right, and we would have to go back and rework it. With the Leader Vision, we can actually see mathematically before we go to press whether or not the plates are in the proper position.”

The Leader Vision measures up to four decimal points, making its tolerance well beyond the tolerance of Weyerhaeuser's printing presses. Consequently, the converter has seen a sizable improvement in job delivery to the press, affording more run time and boosting registration accuracy.

The Leader Vision mounts almost every type of flexo plate. The computer and its software take electronic data from the prepress department and send it directly to the mounter/proofer. A dual-camera locates microdots on a prepress table holding the plate to be mounted. 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 Vision Plate brings the plate up against the press cylinder with a pressure roller and applies the plate exactly to a corresponding microdot position on the press. Operator variations are removed because this system does not require the operator to position the microdots.

The Leader Vision is so tight on its registration that Weyerhaeuser has uncovered tolerance aberrations in its printing plates that it didn't know existed while using its prior manual mounting method.

“We work with plates that are 50 x 80 in.,” Matthews says. “It's not unreasonable to think that there was going to be some tolerance variations. These affect press registration, which is not always evident in traditional mounting systems. The new equipment showed up the aberrations immediately and allowed us to compensate.”

Weyerhaeuser runs a lot of smaller orders of one and two rolls. Rather than spending up to four hours mounting plates for a new one- or two-roll job—and running another job as a fill while the next is being set up—they simply pull the cylinders off the press, go back to the Vision mounter and have the cylinders ready to go back on press in a fraction of the time. Thus, downtime has been greatly eliminated.

“From a quantitative standpoint, we have been able to more than double our production,” Matthews says. “There is no layout that needs to be drawn as you would find on a conventional system. There is no inking of plates and cleaning in the proofing process that you would normally require. We've also been able to move to a larger plate format, so we are mounting fewer plates per job.”

The Leader Print Vision includes a palate of high-tech controls developed by Siemens Energy & Automation (www2.sea.siemens.com), which provides a total solution for the machine's electrical components. Its Simotion® product unites motion control (positioning, synchronous operation), PLC functionality and technology tasks (pressure control and temperature control). Also, Siemens' SINAMICS S120® provides powerful single drives and coordinated drives (multiple-axis applications) supporting vector or servo functions for the Vision mounter/proofer and Siemens SCALANCE X® Industrial Ethernet Switches.

Because Weyerhaeuser is now able to achieve accurate registration far beyond what manual or its prior systems turned out, the printer is looking at the future of plate mounting.“Our throughput is pretty much driven now by how quickly we can move cylinders in and out of the machine—as opposed to the mounting itself. This is quite a difference in this industry.”