Another source of gear marks

Gear marks that are evenly spaced, over distances longer than the pitch of the press gears, may be generated at the die station. Often times butt-cut dies, sheeter dies and rectangle dies, with long lengths of blade running across the web, are required to produce labels to meet customer specs.

These long cross cut dies can at times hit hard enough against the substrate or anvil, to send a shock wave through the press. The wave can pass through the press frame or driveline, or through the web itself. This sudden impact can cause the print cylinders to jump, creating a smudge or "gearmark".

A possible remedy may be to route the web around as many idler rollers as possible, with as much wrap as possible, at the area between the die station and the print decks. This will absorb much of the shock generated to the web itself.

For frame or driveline transmitted vibrations, a dense adhesive backed foam can be laid into the die cavities. This creates a tension between the die and the anvil, absorbing some of the shock to the anvil and to the press, especially while running lower die pressures.

For more information on this issue, please contact: info@teamflexo.com

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