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Virtual Gravure Plant - Coming Soon
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There are several types of web presses used in gravure printing,
including publication presses, packaging presses, product presses, label
presses, and folding carton presses. The printing process is basically the
same regardless of which press is used.
Image preparation begins with camera-ready (mechanical) art/copy or electronically produced art supplied by the customer. Images are captured for printing by camera, scanner, or computer. Components of the image are manually assembled and positioned in a printing flat when a camera is used. This process is called stripping. When art/copy is scanned or digitally captured, the image is assembled by the computer with special software. A proof is prepared to check for position and accuracy. When color is involved, a color proof is submitted to the customer for approval.
The gravure cylinder is composed of a steel or aluminum base, is copper
plated and then polished to a predetermined diameter. Precise diameter of
gravure cylinders in a set is critical. Any variances in diameter, as
little as 2 thousandths of an inch can significantly affect the print
registration. These cylinders are extremely sensitive to scratches and
abrasions. Extreme care is taken when handling and storing the cylinders.
The Doctor Blade and Impression Cylinder
The doctor blade is a simple device used to shear the ink from the surface of the plate cylinder. Pressure is applied to the doctor blade to assure uniform contact along the length of the cylinder. The blades must be angled to cut the surface of the ink, but pressure and angle must be carefully adjusted to prevent premature wear on the cylinder. The doctor blade also oscillates back and forth to prevent a flat surface being worn into the cylinder.
The rubber coated impression roll brings the substrate in contact with the engraved cylinder resulting in proper ink transfer. The impression roll also acts to adjust the tension between print units and helps move the substrate through the press.
The impression roll is made of a tubular sleeve coated with a rubber compound. The cover material is determined by the press conditions. Typically the coating is made of natural rubber, neoprene, nitrile or polyurethane. These impression rolls are typically purchased from an outside vendor rather than made on site.
Web Gravure Inks
See Process Overview Section