August 16, 2010
We have been using a hard vinyl sticky back tape for mounting of our photopolymer plates which seems to work reasonably well. Our supplier has suggested we might try a softer tape but it is more expensive. What are the benefits to doing this?
There is no doubt that hard vinyl tapes can be and have been the workhorse for many printers for many years. They are certainly the lowest cost and the original modern mounting tape but if you are printing anything other than just solid and line work they will do little to enhance your print quality.
Softer tapes are usually of a foam construction and come in a wide variety of densities. The choice of density depends mostly on the graphics that you are trying to print and help minimize dot gain and still achieve good solid print as well. These tapes have a much more complex construction than the basic solid vinyl tapes and also come with a combination of adhesives and liners that can help dramatically improve your print quality and the actual mounting and demounting of your printing plate.
Many thicker cushion mount tapes are used to build up cylinder diameters where plate caliper has been reduced, which is becoming more common as printers move to thinner plate technology but do not want the cost or rebuilding or replacing their existing plate cylinders. There are a wide variety of thicknesses that will suit all plate, sleeve and print cylinder combinations. There are tapes made specifically for fiberglass and other carbon fiber sleeves again to help ensure good repositionability and to minimize the amount of adhesive residual on the sleeve when the plate is removed. This applies the same for steel print cylinders as well. Many liners now have a grid pattern or other patterned structure to ensure that air is not trapped under the tape when it is being applied to the cylinder.
Softer cushion tapes not only help reduce dot gain when the plate is being compressed but also help mask other small defects found on most older plate cylinders and sleeves. That said, you need to ensure that the tapes you buy have a consistent caliper. The better tapes are ground to ensure caliper control; this is something you should check with a micrometer from time to time. A good cushion tape should have good compression and good recovery throughout your print run. Your vinyl tape has little or no give other than the thickness of adhesive and certainly has no recovery.
Because of their superior engineering, soft/cushion tapes are generally more expensive than vinyl tapes just as your supplier has said but in my opinion are worth the extra cost up front based on the benefits that you will see throughout your print runs and extended plate life that you will also be able to enjoy.No Comments