Print Repeat Tips

Print repeats play an important roll in the performance of the finished product and are often overlooked, forgotten or missed in the final job approval. You can have an award-winning package; however if your repeats are too short or long you have to throw the whole product away. In some cases the repeat was within specifications when the job was approved however machine adjustments after the press has started production can alter the repeat. A repeat defect is often discovered too late and is reported by the customer when they try to fill the package with product. Listed below are recommendations to help eliminate repeats from being out of specification.

• The pressman should be supplied with a steel ruler with a length being longer than the largest repeat produced. The ruler should have the full spectrum of measurements; some jobs are measured in millimeters, sixteenths, etc.
• Print repeats should be measured on a smooth surface with the substrate laid out completely flat.
• Plant quality control specifications sheets should list the minimum and maximum print repeats allowable for each individual production run. These specifications should also be recorded on the production run condition folders.
• A print repeat should never be measured after the press rewind has indexed a cut over. The roll should be marked with a flag prior to the rewind cutover and the layers of material removed down to the flag. The reason for this is the web tension may change while the rewind is indexing and alter the repeat.
• After change to the machine settings such as oven temperatures, infeed and outfeed tensions the press should be stopped and the repeat checked.
• The rewind brake plays a role that is often referred to as snap back. The more you increase the brake the more the material will snap back and shorten the repeat. The same is true if you decrease the brake the repeat will increase. This is true when running polyesters, polypropylenes, nylons and other films. But is not an issue when running paper and other more rigid substrates.
• With the nip open install a piece of film under the nip and close the nip. With forty pounds of pressure on the air gauge try to pull the film out of the nip. Repeat this on both sides of the nip and the center as well. If you can pull the film out you have a mechanical problem and or the nip is worn.
• If the nip is not completely flat on the substrate the material can slip through the nip and create sporadic repeats and registration problems.
• One of the best solutions to maintain consistent repeats is to install a repeat micrometer on the press in the rewind area. This will monitor the repeats throughout the production run.

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

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