About the Plate
Photopolymer relief plates are designed for use on the blanket cylinder. Generally speaking, the plates are .045" total gauge. The plates may have either an aluminum or polyester back and a relief between .020" and .030".
Mounting
Photopolymer relief plates mount just like a blanket. When using a quick change bar, go directly to press.
Note: The epoxy used to adhere the quick change bars requires 24 hours to set completely. A form should be included with the coating plate stating what date & time the plate was barred.
With conventional blanket bars, mount the center mark of the plate to the center mark of the blanket clamps. The center of the plate is the center of the sheet. Install the lead edge into the press and register the images closest to the lead edge. Be sure you are square. Lock the lead edge into position. Install the packing. Install the tail edge into position. Be sure you are square. Do not tighten the tail. Snug only. Pull 5-10 sheets. Check register.
Note: Unlike your printing plates, in most cases the image on the coating plate will be wrong reading because you are coating directly to the sheet.
Packing
Photopolymer relief plates typically have a higher durometer (hardness) than conventional rubber blankets. Consequently, for best results on press, use of a compressible under-packing (called a "press pack") is strongly recommended by OEC Graphics. The press packs are available in a variety of gauges to fit most any press undercut. If necessary, they may be used in conjunction with paper packing to match a specific undercut.
Register
Photopolymer relief plates should be close to register if the proper handling procedures
were followed. Make any required side moves first before you adjust the register around the cylinder.
Checking the sheet, the coating will be very close to register on the lead edges. Tighten or loosen the lead edge to achieve lead edge of sheet register. Check the tail of the sheet. Move the image by tightening or loosening the tension on the plate.
Press Settings
Strike a 1/8” bead (3 mm) with the application roller to the plate. When setting the impression cylinder, a "kiss impression" is desired. Back off the pressure until the coating "breaks" or "voids", then apply pressure slightly just until full coating transfer is achieved.
Wash-Up Solutions
When the press goes down, the coating unit and coating plates must be attended to first.
When using aqueous coating, clean the coating plate with clean water only. To remove ink, use alcohol or approved plate cleaners.
When using U.V. coatings, clean the coating plate with isopropyl alcohol.
Caution: Do not use a blanket or roller wash on the coating plate. Most blanket/roller washes contain harsh solvents which will deteriorate the photopolymer coating plate.
Storage
Coating plates must be cleaned before storage. Use recommended cleaners. Store flat or rolled. Keep away from white light.
