Prepress Optimization, Print Quality Management (PQM) and the Total Supply Chain

In general, the flexography PQM programs offered by SGS & Co can be best understood as applying FTA FIRST (Flexographic Image Reproduction Specifications & Tolerances) principles, using a combination of commercial and custom-made products. “We use commercial products for general color applications and create custom solutions for specific customer needs,” reveals Austin.

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Figure 3: The single-color pixel boost step test is run to find the optimum plate cell size for a specific set of printing conditions. Top, close-up of a normal solid dot; bottom, magnification of a Crystal microcell dot.

Following FIRST methodologies, an optimization test is run to verify (or alter) basic variables, such as anilox, plate and tape. Technicians will select the optimization test charts and procedure, based on the specific converter’s needs. Figure 3 is an example of single-color step wedge elements on a press form. This step test is used to find the optimum plate cell size for the specific printing conditions.

Additionally, single-color charts are often run on the same cylinder as the step wedges. An example of a single-color chart is Esko’s Print Control Wizard chart. It is specifically designed to show the optimum screening parameters for flexographic plates exposed under LED plate exposure. This chart contains a combination of elements for automated measurement as well as elements for visual analysis. The primary goal is to find a min dot pixel size (e.g. 16 pixels) and dot percentage (e.g. 0.8 percent) that will enable a smooth fade to zero. Min dots that are too small result in dirty printing. Min dots that are too large result in a grainy appearance or hard edges. The goal is to find the optimum.

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Figure 4: Esko’s single-color Print Control Wizard chart is used to find the optimum parameters for LED-exposed plates. Magnification offers close-up of highlight dot.

A secondary objective is to derive a starting point curve that will be used for the multi-color pressrun to follow. The starting point curve is derived through automated measurement of the randomized 210-point chart. It’s called a “starting” point curve because it’s a single-color curve that will be used for the multi-color profile run. New curves will be derived from the multi-color profile run to be used on the production runs.

One of the core technologies that SGS & Co developed to meet specific converter needs is color profiling. “We mix custom technologies and commercial solutions to get the most from a press characterization,” cites Special Projects Technician Garett Long. “We’re keenly aware of how statistics and bias affect the outcome… In the end, we want a uniform distribution of colors to make a more accurate profile.”

Brand customers and converter partners have access to a broad range of color services. Converters may choose to aim at G7 or a TVI specification. For spot color, SGS & Co can work with SCTV and other metrics, such as Delta E-P. For multi-color, the organization supplies profile charts in any number of colors—from one to eight.

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Figure 5: SGS & Co’s 7-color profile charts enables a combination of custom-developed and commercial products to be used to employ expanded gamut technologies.

“We make expanded gamut easier for our converter partners,” reflects Long. “From a single profile chart (Figure 5), we capture both curves and profiles.” Team members can even adjust profiles for the new curves to be derived from the profile pressrun. “Plate curves are automatically adjusted to reflect minor corrections needed to return the profile to normal. It’s all about getting the best possible data from the least number of pressruns,” he adds.

Prepress Technology

At its core, SGS & Co is a “brand impact” company. Its specialty is to understand brand needs at the “front” of the process and link them with converter capabilities at the “back” of the process.

Prepress tools in the middle of the process assure that this connection is as seamless as possible. While prepress technology has undergone the greatest change of any part of the packaging value chain, the purpose of prepress hasn’t changed. “The goal of prepress is simple” reflects Manufacturing Manager Chuck Schoen. “To alter graphics in prepress in order to print profitably on press.” The economic side of brand impact is based on a simple truth that investing a little extra in prepress up front can save a lot on total job costs in the end.

Delivering brand impact starts with connecting to the brand. Nowhere in the entire process has the advancement of technology been more dramatic. “I remember receiving art boards from customers sent in the mail,” recalls Technical Director Chris Walker. “Then came CDs with digital files, followed by FTP site file transfer. Now we are connected 24/7/365 to brands around the world, using tools specifically designed for artwork approval and connection to prepress.”

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Figure 6: Files move from Mediabox or WebCenter into the Automation Engine where the heavy prepress tasks are performed.

“We integrate with Esko’s Web Center and also use our custom-developed Mediabox system to connect to our brands,” states Monich. “In both cases, the goal is the same: offer the brand an organized way to manage and share its art files and provide a clear approval process—no more fishing through old emails. It gives real-time updates and prepress workflow systems that reduce re-keying of information, improve turnaround time and minimize errors.”

Perhaps the most powerful tool in the prepress department today is the modern workflow system. SGS & Co employs Esko’s Automation Engine to automate processes that used to be done manually. “Just about any task that can be done by a human according to a set of rules, can be done by the Automation Engine,” states VP of Operations Rick Best. “Trapping, step-and-repeat, managing colors, and screening are just a few of the tasks handled by the Automation Engine.”

On the front end, Automation Engine is connected to WebCenter and Mediabox. On the back end, it is connected to CDI Imagers around the world. “From any one location, we can share screened files ready for plate output at other locations around the world,” reveals Best. “This enables load balancing, localization of plate making and sharing of technology.” Prepress done at one location can access state-of-the-art plate imaging and exposure technologies at another location. “Every SGS & Co location has access to the LED plate exposure technologies at our hub locations,” Best discloses.

Screening is another core competency. “We stay up-to-date with the latest in screening technology,” states Schoen. “But more important than the technology is the ability to match the screening to the customer need.” Herein lies the values of SGS & Co’s PQM resources. “We’re finding that for almost all flexible packaging, Crystal screening with plate cells to the edge of the dot, and throughout the entire tonal range, provides the best printed dot quality.”