Enhanced by both the growing amount of printed matter and the variety of inks used, some of which are quite acidic. High-speed printers require closer machine tolerances and coatings that promote longer component life. These coatings, applied to paper-contact surfaces such as rollers and doctor bars, protect against increased wear in these machines.
Engraver rolls are used to transfer ink to paper and historically have used finely scribed lines or engravings to provide a surface that is readily wetted by the inks. Plasma sprayed ceramic-coated ink transfer rolls have found greater acceptance. The ceramic is tougher, provides increased surface area for improved wetting, and offers additional corrosion resistance.
These items are used on web presses and frequently suffer attack from corrosive inks. Recently, though, inks have become more acidic, and improved corrosion resistance has been desired.
A number of rolls used in printing presses are textured to grip the paper and draw the sheets through the press. These varied-size rolls are fabricated from hardened steel and grit blasted to provide the necessary “tooth.” Such rolls wear, oxidize, and go out of specified dimensions, however, necessitating repair and restoration.
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