What’s the Combination
The use of combination printing/processing is not a rarity in package printing—not by a long shot. A printer that has the need could combine any of the printing processes, in addition to converting operations such as foil stamping and embossing.
The value provided by combination printing is that each printing process can bring its own specific attributes to the party, says Andy Colletta, president/CEO of Nilpeter USA. “Flexography and offset printing provide the lion’s share of the coverage on a signature, including the text and four-color images,” he explains. “Rotary screen is often used to provide an opaque background prior to printing, while gravure provides the opportunity for special effects such as high gloss and mirror or chrome-like copy, traditionally used in high-end products such as health and beauty. The digital printing process offers the ability to print variable information, such as numbering or bar codes.”
Steve Leibin, sales manager for Matik North America and representing Omet, concurs with this general assessment. “Each printing process has its strengths and weaknesses. Which print process or combination depends on the graphics required and the run size to best meet the customers’ quality and price objectives. By combining the best of each process, printers can achieve exceptional graphics that sets them apart in the marketplace,” he says.
Specific strengths and weaknesses
Offset printing is commonly the quality standard that all other processes are measured against. “Offset is an excellent process for well-defined images in CMYK/Hexachrome/Opaltone applications and where solids and fine vignettes are required on the same color,” says Chris Davis, sales manager, offset technologies (Codimag and Edelman) for Matik North America.
Dejan Trajkovic, system design engineer for Gallus, adds, “Offset brings lower set-up costs due to the economical production of the printing plates and gives the highest quality printing in large quantities.”
Gravure printing is another standard bearer of high-quality printing, although typically associated with long production runs, notes Denny McGee, president of MPS America LLC. “Gravure provides high-quality printing, great heavy laydowns of metallic and florescent inks, and is commonly associated with long runs based on print cylinder life,” he says.
Terry Trexler, product manager for Gallus, agrees, saying, “Gravure brings rich, deep metallics and basic printing at very wide widths and high speeds.”
According to McGee, rotary screen printing is the “master at heavy laydowns of inks and coatings.” It is typically used for adding opaque white or as a primer for film stock, notes Davis.
With its ability to provide good opacity, Trexler says that it is used to deliver “nice white opaque laydowns on clear material to create the ‘no-label’ look.” In addition, screen printing brings touch and feel to applications—with ink laydowns up to 280 microns—and can provide Braille and touchpad printing in roll to roll, he adds.
The full range of what screen pringing adds to the application is determined by the screen itself. Joe Posusney, marketing manager for Gallus, says the company offers eight types of Gallus Screeny that provide a range from fine lines to relief printing that delivers tactile surfaces and Braille effects.
Digital printing brings two unique capabilities to the table—excellent turnaround for short-run needs and variable data printing. Different digital technologies are available, such as inkjet and digital offset as used by HP Indigo.
“Digital has outstanding print quality, but low print speeds—too low for practical volume printing,” says Paul Teachout, product development manager for Aquaflex. “Digital is an important support process when used in single-color variable information applications.”
According to McGee, digital offset has proven itself in short-run, high-quality applications in a wide variety of end markets. “In addition, ink compatibility and first-pass register accuracy allow for combining flexo, rotary screen, and foiling methods in-line, or more commonly off-line,” he says.
McGee believes that inkjet holds much promise as a four-color printing process that can provide higher operational speeds and, potentially, lowest-in-class digital ink costs. “Also, inkjet appears to be easier to adapt to a traditional printing press allowing it to play an expanded roll where it meets the technical and market requirements for combination printing,” he says.
For the North American label market, flexographic printing is the major process used as the foundation for additional combination processes. In addition, there is a growing recognition that flexo can provide comparable functionality offered by other processes. “Flexo overlaps the other traditional printing processes, offering high-quality four-color process printing and very good solid coverage,” offers McGee. “Flexo can produce its own level of tactile feel, which can suffice at times versus using rotary screen.”
Teachout expands on this point and takes it a step further. “Flexo’s evolution as a printing process has come so far in recent years that we find combination processes to be more the exception than the rule,” he says. “Today, flexo successfully rivals offset in print quality and the ability to lay opacities, coatings, and comparable screens.”
What today’s enhanced flexo printing capabilities offer is economy, allowing brand managers to make decisions around price versus quality. “Brand buyers look for the highest quality for the lowest price,” notes Teachout. “Sometimes rethinking the criteria for ‘highest quality’ can lead to substantial cost reduction. It’s a delicate balance, but in today’s highly competitive markets, cost reduction is a compelling argument for change. The modern flexo press is the ideal change agent—delivering both quality and economy in short and long runs.”
While each of the printing processes has its own particular strengths, each has certain limitations also. For example, gravure has its longer turnaround time and equipment expense (cylinders). Digital has lower speeds and higher consumables expenses. McGee notes that rotary screen typically runs UV inks, accompanied by heat management issues when running temperature-sensitive film materials. In addition, speeds for rotary screen are typically lower than other traditional presses.
The impact on press run speeds is always a concern and is not limited to screen printing. “A major issue in combination printing is with the addition of each process, overall production speed is compromised,” says Colletta.
Besides these specific, process-related tradeoffs, general concerns come from the knowledge and skills required for each of the processes. “In-line combination processes require the user to understand the strengths and tradeoffs of each process, as well as having the procedures to assure each process is well controlled,” observes Mike Lawrence, Comco product management for Mark Andy. “Added flexibility brings along the tradeoff of increasing system complexity.”
There are other factors to consider. “The prepress side of combination printing requires the converter to have all the necessary requirements for film or film-less production of plates, rotary screens, etc., in-house or they have to work with an outside source,” notes McGee. In addition, Leibin says that combination printing can add to set-up times and can also increase a job’s waste factor.
Combination printing will continue to expand in the package-printing arena. “We expect that the use of combination printing lines will continue to grow,” predicts Lawrence. “Consumer product companies will keep evolving their graphics and package constructions to differentiate their products on the store shelves.”
Press manufacturers are providing the tools needed to make combination printing more and more feasible. “The ease with which the print processes can be combined is certainly driving the trend towards more combination printing,” says McGee. “Servo-drive, shaftless technology and developments refined by clever engineers with 20-plus years of combination printing experience are providing easy systems to use when compared to early-on combination printing equipment.” pP
Process attributes at a glance
• Water-based and solvent-based flexo are very strong in achieving high solid densities, low ink cost, and vibrant color in short, medium and long runs on all label and packaging materials.
• UV flexo is a strong process for printing a minimum dot and high solid densities, but the ink cost is higher than with water-based.
• Rotary screen is the strongest process for solid density, easily achieving the greatest ink film thickness. The run speed is relatively slow—200 fpm. This is the strongest process to achieve the highest levels of opacity.
• The rotogravure process is excellent for control of the minimum dot. The metallic inks available are excellent and vibrancy of color is very good, as are maximum run speeds. Prepress cost and cycle time are relatively high.
• Offset prints minimum dots very well, has relatively low prepress/plate costs, and the cycle time for prepress is relatively short. It can operate at high run speeds. Offset printing isn’t as strong as the other processes in regards to maximum solid densities, vibrant colors, or metallic inks.
• Since there are many very different digital processes, the characteristics of them differ greatly. The prepress cost and cycle time are typically low, but consumables costs are high. Digital printing performs best for fast turnaround, small quantity orders of high value or high margin products.
Mike Lawrence, product management – Comco, Mark Andy Inc.