Converters today have the luxury of choosing from a variety of mounters. Plate mounting devices come in all styles, sizes and shapes, but they all exist to assist the operator in getting the plate into the correct position. “Mounters are divided basically into three levels,” says David Cloud, vice president of sales for Conversource, Chesterfield, Mo., a supplier of flexographic pressroom products. First there are the mechanical mounters, which usually sell for under $1,000, Cloud says. Conversource manufactures its own mechanical unit, the QualiMount.
Then there is the high end, with prices at $10,000 or higher. These employ a range of magnifier and video technologies that enable the operator to examine the mounting process on a screen. They are sophisticated and easy to use.
High power microscopes
Mark Andy Inc., Chesterfield, Mo., produces a series of plate mounters called the “PM” series. The system utilizes two high power (20X) microscopes and an adjustable table to align photopolymer flexographic or rotary letterpress plates onto the plate roll cylinder to ensure perfect register. The units are fast, allowing an operator to mount a four-color process job in a fraction of the time required by conventional mounters. It also comes with a stickback tape dispenser. Register marks on the plate are visually aligned with a stationary hairline on the plate mounter, which is parallel to the plate roll (roll is held in position by pneumatically operated side clamps). Fine adjustments are made by a screw-type knob that moves the plate table to the exact register position. Once the register marks are aligned using the microscopes, the user touches the plate to the tape affixed to the roll cylinder, releases the plate clamp, and turns the cylinder to complete the tape attachment.
The Snap-Fit Mounting System, manufactured by Ireton Equipment, Dayton, Ohio, uses a different process. “We use a physical reference instead of a visual one for mounting,” says Rob Ireton Jr. These references can be registration marks or bearer bars that are already being used in the printing plates.” The Snap-Fit System has two U.S. patents and is patented in 13 European countries.
When using the Snap-Fit System, the operator first aligns the plate and then attaches it to the cylinder. Estimated time for mounting is 15 seconds, Ireton says. “Since the system uses a physical lock instead of a visual reference, it makes the repeatability of plate placement much easier,” he says. Recent innovations on the system include a bearer bar PRR plate, in which the bearer bar and the PRR plate lock together. A sliding PRR plate allows the operator to center the PRR plate and printing plate to the cylinder, while the cylinder remains in a fixed, locked position. It can also be used to step and repeat printing plates. The improvements, Ireton adds, can be retrofitted to any existing Snap-Fit System.
The Mount-O-Matic Table-Top mounter from AV Flexologic, based in the Netherlands, is distributed in North America by Anderson & Vreeland. The unit utilizes a system based on two coordinates (cross marks) that have been applied on the printing plate. The plate cylinder is placed and fixed onto two adjustable cylinder racks. The position of the coordinates can be determined by means of a collapsible ruler.
The mounter is provided with two cameras and a split-screen monitor. Each camera registers half an image, one on either side of the split screen, so that halves of the cross marks are visible on each. The two halves then make one cross mark, indicating precise alignment. The cross marks are enlarged approximately 8 times by means of the zoom lens. The unit also comes with an optional vacuum table.
Propheteer International, Palatine, Ill., also manufactures a video mounter using the split screen technology, designed in cooperation with Dow Industries, of Wilmington, Mass., in 1984. The cameras magnify plate register marks to 20X.
An AC motorized drive raises and lowers the print cylinder under the cameras, and allows fast movement for large repeat changes and fine adjustment. A foot pedal controls vacuum pressure for fine adjustment. Yet another high-end video mounting system for narrow web converters is the Viper, manufactured in England by J.M. Heaford Ltd. It operates with a microdot alignment system and register crosses, and utilizes an electronic control system with high-powered video cameras.
What’s in a tape?
Plate mounting tape, also known as stickyback, comes in two basic types: hard and cushioned. The hard tape is vinyl, and is best for printing solids, lines and reverses. “The harder the tape, the harder it pushes the ink into the substrate,” says Chosid of Conversource. “You use hard tape because you want no ‘give’ at all — you want all the ink coverage," adds Cloud.
Cushioned tape is used for more complex work, including four-color process. “The softer it is, the less it does, but the less dot gain you have,” notes Chosid. Cushioned tape has more forgiveness. Popular tapes on the market today are from 3M, Harley, and Edward Graphics. The first step up from hard vinyl is the high density cushioned tape, which has some ‘give’ but not much. Beyond that are two or three other levels. 3M offers a medium high density, a medium low density, and a low density, which has the greatest cushion.