Increase Anilox pressure for trailing edge void problems

Paperboard Packaging, Oct, 2004 by Cordes Porcher

Problem

Name: Trailing Edge Void

Signs and Symptoms: It appears as line, curve or whatever shape the solid is printing. This effect will be more noticeable the thicker the plate.

Location on sheet and/or printed elements: This problem is found only at the trailing edge of a solid.

Description: This is an area void of ink found at the trailing edge of a solid. This void will conform to the shape of the solid.

Diagnostic Process

Evaluation: The key elements to identifying this problem are as follows:

1. Only found at the trail edge of the solid print.

2. Under examination with a magnifying glass, the area in question will be free of ink.

3. When the printing plate is examined, ink will not be present on the trailing edge of the solid area of the plate.

Tools: Magnifying glass, 10 to 12X.

Cause: Not enough anilox roll pressure to the plate impression.

Note: Thicker ink film will allow the use of less pressure. For example, change from a lower volume to a higher volume anilox roll.

If more prominent on one side of the plate, the anilox roll may not be parallel to the plate cylinder, the plate may be worn on that side, or there may be a restriction in the travel of the anilox roll on the side in question.

Collateral Effects: Can lead to poor traps and print voids at the ends of solids. Failure to match color or color shifts can result from dots not printing completely.

Treatment

General Measures: Increase anilox roll pressure by small amounts until problem is eliminated. Caution: Do not apply more pressure than is needed. This will create additional unwanted problems.

Chemicals: None.

Extreme Measures: If additional anilox roll pressure to the plate will not resolve the problem, the following may need to be reviewed. Examine the relationship between the plate cylinder and the anilox roll and ensure they are parallel to each other and total indicated run out (TIR) is within original equipment manufacturer (OEM) specification. Remove plates and return to plate supplier for evaluation. Look for mechanical blockages or failures in the anilox system.

Prevention

Proactive Steps: Ensure press is maintained to OEM specification. Press controls provide accurate setting information. Plates are reviewed upon arrival for levelness.

Where to seek help: Contact your equipment supplier for specifications regarding parallel and TIR. Contact your plate supplier to review plate manufacture, imaging and mounting.

Cordes Porcher is a technical specialist in high graphics on corrugated for Bobst Group USA. He travels the continent helping the post-print industry improve and understand the printing process. Porcher has 15 years of teaching experience, with the last 13 spent in printing. He can be reached at 888/226-8800 or 973/226-8000 ext. 5270 or e-mail cordes.porcher@bobstgroup.com.