Substrates and the substantial benefits they bring to highly specialized print processes, like flexography, are not to be ignored, taken for granted or otherwise dismissed.
Optimizing ink to substrate is essential in successful printing. Great attributes of a substrate, particularly plastic packaging, merit mention:
- Plastic packaging plays a key role in food freshness and preservation, which reduces waste
- Such substrates also play a vital role in critical medicine packaging, as well as protecting and sterilizing medical devices and supplies
- Transportation of product—whether it’s a shrink film wrap for bulk bottled water or securing food in a delivery service package—speaks to the protective properties rendered
- Flexible packaging also serves to inform us of very important facts printed on the package—think product information, directions, warnings, ingredients and nutrition data. Customer engagement is made possible through a mobile device, as in stores, shoppers often scan packaging for price comparison or recipes. In certain applications, a virtual reality experience can also be launched from scanning a package
Benefits noted. Now, let’s focus on optimizing the flexo printing process used to produce eye-catching and trendy graphics that have shelf appeal and can sell the product.
There is a lot to consider when identifying substrates and inks that deliver the desired results.
- Cost: Since we at Berry Global manufacture the substrates we print on, we have a lot of control and are always looking at ways to reduce cost. Light weighting packaging is one way to take cost out of the package. Reducing the weight limits raw material consumption; at the same time, it helps the environment
- Sustainability: Berry has a tremendous focus in this area. Utilizing recycled, biodegradable and compostable material in our substrates ensures we are making an impact
- Regulatory: Do your substrates and inks pass regulatory requirements for the end use? As these requirements become more and more stringent, identifying this at the optimization stage is critical
- Ink Usage: The optimization stage is a good time to start thinking about how to minimize ink usage. Among avenues we’ve explored to achieve this is UCR/GCR. This process reduces the number of more expensive CMY inks by replacing the neutral areas with black. Done correctly, quality is not sacrificed. We also utilize expanded gamut (EG) printing for ink savings. Typically, EG isn’t something that’s thought about until the fingerprint or characterization stage. But considering this approach during the optimization stage allows for better execution throughout the process
- Ink Adhesion: What challenges will you face when preparing substrate to accept ink? The effectiveness of your pre-treat is critical. If the typical methods are not sufficient, you may consider adding a texture to the substrate or an adhesive layer to improve adhesion. You also must consider what type of adhesion test will be required during production: tape test, heat or freeze tolerance. Some of our products end up in a shower environment. These products must endure what we call a soapy/squeeze test, which involves submerging the product in water for 24 hours, squeezing several times and then observing for adhesion
Fills & Foibles
One printing process we use to print our cups is indirect flexo. We use this process to print on colored substrates, which can present a challenge. Print color will shift because you can’t totally block the substrate color with white ink.
Through optimization, you make the white ink as opaque and bright as possible and you go from there. Know what to expect. See the color shifts during optimization and subsequent fingerprinting and characterization. Predict the color and proof it.
It’s a little trickier when dealing with clear substrates. What I mean by trickier is that a lot of the time we overlook how the package is going to appear filled, which depending on what it’s filled with, could have a dramatic influence on the print color. Going through the optimization, fingerprinting and characterization steps, this fact is not always as apparent or thought about as it would be if you were printing on a colored substrate.
Clear cups printed with the indirect flexo process illustrate the effect fill has on the print color. Fills that are translucent or light have minimal impact, but as we get fills that have color or are darker, the color shift becomes more dramatic. The worst case would be a dark blue drink. This has a substantial impact on the print color, and in most cases, would be unacceptable to a customer.
So, what can we do at the optimization stage? Step one is to consider the final use for the package. Understanding what is put into the package could have an impact on print color. With this, you then know what you need to do to improve.
Maybe you have options with anilox to lay down more white ink. You could look at plate screening technology that would increase your opacity. Also, multiple hits of white could be considered. Other options may include a different print process; some of the hybrid presses have inline rotary screen or digital print.
As you go through the optimization process, and subsequent fingerprint and characterization, the most important thing is that you and your customer are aligned. All the details of the process and possible limitations have been thoroughly discussed. And when the final package is delivered, all expectations have been meet.
Birchler presented this information as part of Virtual FORUM 2020 in the session titled Press Optimization: Straight from the Mouths of Printers. FTA members can watch all five presentations from this session, as well presentations from the other five Virtual FORUM 2020 technical sessions, on MemberConnect.