Ink key control in a printing press including lateral ink spread, ink saturation, and back-flow compensation
AssigneeQuad/Tech, Inc.
InventorsJohn C. Seymour, Chia-Lin Chu
Life of this patent
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Abstract
A method is disclosed for correction of the effects of ink back-flow and lateral flow in the inking system of a web-offset printing press. A plate coverage equation dependent on plate coverage is used to compensate for ink back-flow into the ink reservoir. An ink key distribution function is utilized to correct for the blurring effects of lateral ink spread caused by the action of vibrator rollers. A correction is also made for the ink saturation effect. The method is applicable to an ink key preset system.
Claims35
A method for determining initial settings for a plurality of ink control devices in a printing press wherein the ink control devices control the amount of ink supplied to respective zones of a first roller, wherein ink is transferred from the first roller to a roller train and then to a substrate to print an image, wherein the ink control devices are associated with respective ink key zones on the substrate, and wherein the roller train includes a plate cylinder and a vibrator roller that moves back and forth in a lateral direction with respect to the longitudinal direction of movement of the substrate, the method comprising,
- determining an ink key distribution function by means of a press test by relating the amount of ink supplied by a single ink control device to the distribution of ink on the substrate in a plurality of affected ink key zones due to the lateral movement of the vibrator roller,
- determining an ink saturation density function by relating an optical density of ink on the substrate to the ink film thickness on the substrate, and
- computing an initial setting for each ink control device based on the ink key distribution function given a plate coverage value for a respective ink key zone and a desired optical density of ink on the substrate.
A method for determining initial settings for a ratchet and a plurality of ink control devices in a printing press wherein the ratchet and the ink control devices control the amount of ink supplied to respective zones of a first roller, wherein ink is transferred from the first roller to a roller train and then to a substrate to print an image, wherein the ink control devices are associated with respective ink key zones on the substrate, and wherein the roller train includes a plate cylinder and a vibrator roller that moves back and forth in a lateral direction with respect to the longitudinal direction of movement of the substrate, the method comprising,
- determining an ink key distribution function by relating the amount of ink supplied by a single ink control device to the distribution of ink on the substrate in a plurality of affected ink key zones due to the lateral movement of the vibrator roller by means of a press test,
- determining an ink saturation density function by relating an optical density of ink on the substrate to the ink film thickness on the substrate, and
- computing the ratchet setting and an initial setting for each ink control device based on the ink key distribution function given a plate coverage value for a respective ink key zone and a desired optical density of ink on the substrate.
Dependencies are inferred from the claim text.