Plate Processing & Storage
Plate imaging is a critical process. For optimal registration and consistency, it’s best to image all plates in the same direction on a digital imager. Optimize your plateroom to enhance your exposure, processing, handling, cleaning and storage variables. Prolonged exposure to UV light or the environment can lead to poor plate longevity, higher dot gain and decreased density.
When it comes to storage, plates should be cleaned with a compatible plate cleaner, dried properly and light protected after each pressrun. Storing plates in an area with high UV non-filtered lighting will reduce shelf life and reusability.
Sleeves
[perfectpullquote align=”right” cite=”” link=”” color=”#1a1d22″ class=”” size=””]“Work closely with your designers and suppliers to develop good, repeatable artwork that can be printed to your specifications.”[/perfectpullquote]
The majority of the folding carton business requires a larger repeat sleeve and sleeve width. It is critical that print sleeves are consistent in TIR (total indicated runout) and have even surfaces. Your sleeve supplier can provide you with a certificate of analysis. Also, if you see a print void in the sleeve, it could have a low spot, which may indicate the sleeve has been damaged. Most damage is visible, but some can hide inside the sleeve.
Print sleeves for folding cartons come in various materials, including fiberglass composite, urethane and nickel (thin). There are also cushion sleeves available for special applications.
Sleeve manufacturers have been working to reduce the overall weight of larger sleeves by improving raw materials in order to make them more durable and lighter. In addition, there are sleeve handling systems to assist operators and virtually eliminate handling. Consult with your sleeve manufacturers to determine what type of sleeve will work best for your facility.
Mounting Tape
When selecting an optimal cushion/plate combination, you will want to use the firmest tape possible that offers the least amount of impression, without influencing dot gain and print slur. This will enhance plate longevity and prevent failure on long pressruns.
In addition, it is important to optimize the cylinder and plate size adhesion to prevent plates from lifting on edges or allowing air bubbles to form during the run. These factors are all very common in folding carton printing.
[perfectpullquote align=”full” cite=”” link=”” color=”#41508b” class=”” size=””]“What I have learned, more than anything, is that the possibilities are endless; I can see great opportunity for growth and improvement as our process continues to evolve with new and exciting innovations.”[/perfectpullquote]
Inks
Water-based inks are more common in folding carton printing; viscosity and pH are key to consistency on paper, along with print sequence.
Print sequence is generally dark to light, improving the wet trapping of the yellow ink. Automatic ink pH/viscosity control systems work to improve management during runs. Inks also need to be filtered due to paper dust residue getting into the ink system.
Coarse papers can damage the plate dot surface throughout the printrun, so check periodically. Some printers struggle with static discharge from paperboard. There are systems to vacuum and reduce static prior to print impression and they can keep ink cleaner during a run.
Quality Control
Most important, measure! Measuring is key! Have a system in place to manage and monitor print density, dot gain, ink pH and ink viscosity. It’s always a good idea to keep these records in a system that can be referenced for quality control for each item you’ve run, as well as the history if there are multiple runs.
Quality control can also be moved upstream into the plate making areas to include laser ablation checks on your digital imager, as well as final plate inspection using a plate analyzer.
In closing, I hope these key areas identified will help you keep on the right track for folding cartons. I understand not all the information here may be fully applicable in your environment, but it might help you see opportunities that could be applied to your processes.
About the Author: Greg Wishon, technical service consultant at DuPont Advanced Printing, has more than 33 years of experience in the printing industry, with 25 of them working in the paperboard industry in the preprint linerboard and folding carton segments. He is known for his expertise in prepress, plate making and printing for the paperboard industries.
Greg earned his associate’s degree in printing technology from Vincennes University in 1985, and a bachelor’s in business from Indiana Tech in 2002. He and his family reside in Carmel, IN.
You must be logged in to post a comment.