Up until very recently, color consistency has remained very challenging to implement. The sheer variety of printing processes, inks and substrates have created a significant challenge for brand owners and converters to achieve color consistency. Some substrates, such as paperboard and corrugated cardboard, are more absorbent, which can affect how the color of the substrate itself interacts with the ink and affects the color. Substrates aren't the only consideration either – there are various printing processes, from offset, flexo and gravure to digital printing, and all use different types of inks.
“This is becoming a real priority for brand owners now,” says Federico D'Annunzio, head of product development for DigiColor Technology at Bobst. “Until recently, there was only a little culture of color management within companies, but now it is growing and becoming strategic. And it is not enough anymore to have colors that appear to match with the naked eye. The industry has developed very advanced instruments that can measure the precise Pantone color. There is nowhere to hide for converters on this issue, and it is our job as a supplier of equipment and services to find solutions through innovations.”
Bobst recognized the urgency of the challenge years ago, the company says, and put several initiatives in place to find solutions. For example, it founded the REVO project, an ambitious flexo industry initiative involving multiple partners, which aims to "digitally" standardize and automate the flexo process, from prepress to print delivery. Color consistency is a major element of this.
The REVO 7-color Extented Color Gamut (ECG) printing, developed by the REVO Technology Team of industry suppliers, is now a well-established turnkey DigiFlexo process that flows from prepress through to production output. As well as REVO, there are also other Bobst industry partnerships aiming to achieve optimal ECG printing, including smartECG, which is focused on flexible packaging.
ECG printing uses three additional ink colors – orange, green and violet (OGV) – on top of the conventional colors of cyan, magenta, yellow, and black (CMYK), enabling a match with 90%+ of the Pantone book, compared with approximately 60% previously. This means there is no need to keep huge inventories of spot colors – the majority of color positions can be generated without having to use spot colors. But spot colors can still be added if required.
The digitization of color matching has made color conformity with the job master request possible. With the new DigiColor system, brand owners can validate the colors through a digital version of the final product. It means that brand owners can have reassurance around the color matching of their packaging worldwide, irrespective of the geographical location of the printing facilities or the different ability of the press operators.
“If a converter uses a REVO package, they can start with ECG and be successful from day one,” explains D'Annunzio. “Because REVO packages contain inline color measurement and standardization of all print elements, including plate, anilox, inks, prepress, substrates and inspection, this provides the consistency. We also provide information and support to converters so that adoption of ECG can be as smooth and fast as possible.”
The latest example of an ECG-ready CI flexo printing solution from Bobst is the 20SEVEN, which has notable improvements in mechanical design and process control to make the machine a fit for the requirements of the 7-color ECG printing process.
Meanwhile, Bobst also founded Mouvent as its digital printing competence center in 2017. Mouvent has already revealed several printers that can all print up to seven colors on a large variety on substrates – paper, self-adhesive and wet-glue labelstock and flexible materials – at high production speeds and with complete color consistency.
What about corrugated?
The quality and color consistency with flexo on corrugated has often suffered, and more complicated images, coloring and photo-quality images are usually not possible. What’s more, the cost of ink and plates can be high, and if any of the artwork is changed, new plates need to be made.
Bobst introduced THQ (Très Haute Qualité) FlexoCloud Technology to change all that. Bobst, along with its industry partner Graphilabel, pioneered a solution that is associated with a large color range with a 4-color process, perfect color density with solid printing and outstanding quality on a large range of liners. It is associated with ultra-high precision, positive and negative line printing and smooth transitions, from 0 to 100% coverage.
In 2019, Bobst introduced DigiColor, the very first closed-loop color control system in the flexo industry, the company says. Color is measured inline and adjusted on each print unit to match – in a few meters – the target color values. Each of the seven ECG inks is split into a darker and a lighter ink, which are mixed inline to match the targeted Delta E. DigiColor can make subtle adjustments as needed while printing. For example, if the substrate absorbs a greater quantity of ink than expected, and the Delta E Target is not matched, the system will automatically adjust to utilize more dark ink, ensuring perfect tone accuracy and Delta E color matching. The flexibility in color management that was traditionally exclusive to digital printing and, partly, in offset, is now available to flexo printers.
DigiColor completes the Bobst path to full digitization of the flexo process. Print pressure, register and now color, are managed by digital automation (sensors, servo motors, Artificial Intelligence) making digital and digital flexo widely compatible and closer in performances, also on short runs.
For the first time, it is possible to transform the final printed product from DigiFlexo back to a digital file to be able to compare it with the original digital native file. The printer extracts digital values from printed job, producing a “digital twin” of the original file. This means that brand owners can review a digital twin and validate the colors from the original digital file – no more guessing – just facts. This effectively “closes the loop” starting with a digital file, utilizing digital automation to complete the job, and validating the output with another digital file.
“The feedback we have heard from converters – and the brand owners who are their customers – who have utilized our innovations so far, including REVO presses, is that they are extremely happy with the consistency,” says D'Annunzio. “Now with DigiColor we go to the next step – outstanding color consistency but with an entirely automated process. This is a major evolution and I believe it will revolutionize color consistency management in the print and packaging industries.”