Optimizing Fixed Palette (And What it Means for Label Printing)
Recent studies and trials aimed at optimizing Pantone simulation suggest that the fixed palette approach is ready to revolutionize the flexography and label industries. The change is due specifically to advancements allowing for unprecedented process control and consistency, as well as the development of new tools designed to pinpoint which process parameters are failing so they may be addressed quicker.
A recent trial by Soma Engineering, in partnership with Apex International, has provided hard data supporting the idea that process variable elimination and optimization of remaining processes is the key to maximizing the number of Pantone simulation possibilities using 4-color fixed palette. The study also produced data comparing the 4 color fixed palette to 7 color. The trial was conducted on a Soma 8 color gearless press OPTIMA.
Using CMYK plus orange, green and reflex blue, 1,412 Pantones within a ΔE of 2 or approximately 81 percent of Pantones were able to be hit. Comparatively, 1,184 Pantones were hit using just CMYK within the same ΔE. However, when silver was included, an additional 1,184 in metallic Pantones were hit to bring the total Pantone simulation to 2,604. Also hit were 1,519 Pantones using 7 color and 1,302 using 4 color within a ΔE of 3. Including metallics, 2,604 Pantones were hit, which is beyond what any other known CMYK trial has achieved.
Four-color fixed palette has two distinct advantages over 7 color. The first is a matter of variable elimination. Printers need to determine if the additional 228 Pantones are worth the inclusion of three additional variables. The second advantage relates to flexibility. It is estimated that 95 percent of printers only have 8 unit presses. Four-color fixed palette allows for inclusion of metallics, various lacquers, double white and other options that create value and subsequently command a higher price point.
The demand for optimized fixed palette is only expected to grow as brand owners demand better color consistency with shorter run lengths and just-in-time production. Chief among these concerns is the ability to create color consistency across multiple markets ensuring that the same values and same Pantones can be printed on labels just as they can on films. And color consistency is certainly an issue when it comes to transitioning to a fixed palette process.
The trials show that specific attributes of Apex International’s GTT engraving perform exceptionally well with fixed palette. It has a tolerance of 2 percent on volume and ink transfer. GTT engraved rolls are 90 percent opening while maintaining wall stability. Ink flow is more consistent and unobstructed, subsequently solving spitting issues and producing a controlled, smooth laydown. All these things contribute to the results experienced with Soma.
Calibration: The Key to Optimized Fixed Palette
Flexographic printers have developed some bad habits, none worse than consistently changing and compromising to achieve specific results by adding new variables to their printing process. Instead of taking the time to correct problems when they arise, printers bypass issues creating ad hoc solutions for individual projects only to solve the same issues again and again. And this approach is not without consequences. Corrections waste time and materials and take away from profitable operation.
The systematic elimination of variable components in the printing process is the only true way to gain the control necessary to effectively optimize fixed palette. Variable elimination requires a full understanding of the manner in which the various print process components interact with one another, and a means by which to test the variable when issues arise. Generally, printers understand the relationships that exist between inks, plates, anilox and the other components that make up the printing process. However, the industry has lacked a means to verify which variables are causing problems and eliminate them.
But now, for the first time, there’s a true calibration method to identify the source of issues in the flexo process. It’s a method that enables fixed palette Pantone simulation to be produced with consistency, efficiency and with high-quality results within a high-volume production environment.
A process control reference or calibration anilox roll is the key to process variable elimination and optimized fixed palette. These specialized, duel-engraved anilox rolls allow printers to check the performance of printing plates and the anilox when issues arise. Calibration rolls can also audit new anilox rolls, allowing printers to identify issues before they interfere with production.
The process control method of variable elimination using a calibration roll requires the use of additional control blocks within the design in magenta, cyan, yellow and black. These control blocks are used in conjunction with the calibration roll to implement the process control method. For example, in situations where 100 percent solid density is correct, 50 percent dot gain is correct and 10 percent dot gain is correct, a design deemed incorrect indicates the process issue is repro. Conversely, if 100 percent solid density is incorrect then the calibration roll can identify which variable is problematic. When the calibration roll replaces the anilox and density is corrected, the solution is that the anilox roll used in that station is either dirty or worn. However, if the density remains out of spec, the solution is related to poor or out of specification ink. In other situations, where density is correct but dot gain is problematic, using the calibration roll can reveal one of two possible corrective actions. If the calibration roll corrects the 50 percent and 10 percent dot gain, then operator pressure or anilox TIR is out of spec. Conversely, if dot gain remains out of spec, the solution is related to operator pressure, plate sleeve TIR, mounting tape or plate wear.
The adoption and widespread acceptance of optimized fixed palette is entirely dependent on the use of calibration tools to systematically eliminate variables from the printing process.