Flexo Plate Evolution
Digital plate processing has altered the landscape in flexography. The conventional systems still abound, but digital is taking market share, and some new equipment is poised to gain attention.
By Jack Kenny
DuPont changed flexographic printing forever with the introduction many years ago of photopolymer plates. The company continues to exert powerful influence on the flexo industry today with its thermal plate processing system, which it calls FAST. In the not-too-distant past this dry process was accompanied by a digital plate imaging technology making use of laser ablation of plates. The two major equipment providers were Esko and Creo (now Kodak).
Outside view of the Stork Prints Digital Laser Engraver
“Converters need to milk every penny out of the equipment that they have,” says Michelle Garza, general manager of RBCOR, a plate supplier based in San Marcos, CA, USA. “If they go digital, they can’t pass the increased cost along to the customer. They have to eat it. We are noticing that people are holding back from going digital. Some say they don’t see a big difference in quality. Some don’t need high end quality and don’t need to go digital.”
Just about every aspect of the digital plate is criticized by someone in the flexo field: the plates are sticky, the lifespan is lower on press, they are inconsistent. On the other hand, those who have experienced success with digital plates say the opposite: the quality is consistent every time, they are just as durable as conventional plates, the sharper dot structure enables higher quality printing.
Strictly speaking, there are six procedures used today to produce a photopolymer flexo plate:
• Analog aqueous, or water wash: Plates are created using traditional film output, traditional plate exposure with film, and washout using a water system.
• Analog solvent wash: Traditional film output and exposure, solvent wash system.
• Digital ablation aqueous: Electronic image file sent to laser ablation unit, which ablates a plate covered with an aluminum mask. UV exposure and water wash follow.
• Digital ablation solvent: Electronic image file sent to laser ablation unit, which ablates a plate covered with a carbon mask. UV exposure and solvent wash.
• Digital ablation thermal: Masked plate is ablated digitally. UV exposure, then finished in dry thermal processing unit.
• Digital laser engraving: Laser engraves complete image into exposed plate or sleeve. No other steps required.
Inside view of the Stork Prints Digital Laser Engraver
“At this point, our customers dictate what we do. If a customer is doing high end process we will steer them toward digital, which will give them smaller dots. Still,” he adds, “quite a few don’t want digital, so for them we make the plates using the analog system.” Why? “I think it’s fear of the unknown, perhaps. They are set in their ways.”
Bernard says that the price for an analog or a digital plate is “nearly all the same. With analog you need to produce film, so there’s a slight increase, just pennies.”
About 55 percent of the plates made by Trinity Graphic USA now are produced digitally. “If I could convince customers that for what they are trying to print they should use digital, I will try. When digital imagers first came out, we gave away digital plates with the analog ones, just so they could try them. Some made the change, some didn’t.”
Bernard is among those who say that water wash plates are good for line work, but not as good for process printing. That view is challenged by Joe Tuccitto, manager of training and technologies for Anderson & Vreeland, Bryan, OH, USA. “We manufacture our own aqueous systems. For a while you didn’t hear people talk about aqueous, but we have made some major improvements. Filtration in the polymer removal systems have come a long way in the past few years. Our system, which we call Whirl-Away, sends the polymer into a bag, which is easily removed.
“With solvent wash, the drying time is significant, a minimum of two hours to get the solvents out of the plates. With aqueous it’s five or six minutes. In that time you have complete dryback. We have been doing well in the label market with aqueous. We have eliminated the mess that caused complaints in the past, and we are pushing it now.” Aqueous systems come with the advantage that they use no solvents for processing.
But solvent systems are popular and familiar. Many converters who utilize digital imagers also maintain the analog plate processing equipment that has served them so well over the years. To them, it depends on the customer and the job to be printed.
Ablation is the result of the action of the laser inside the digital imager upon the carbon mask that covers the plate. In the ablation systems marketed by Esko, Kodak, Anderson & Vreeland, and others, the ablation of the mask permits removal of the photopolymer during the analog washout or the thermal removal process.
“The laser in the digital imager just ablates the carbon layer on the plate,” says Tyler Harrell, solutions and innovations manager for Esko, Vandalia, OH, USA. “The exposure process and finishing process is just as it was prior to digital imaging. We are currently in last stages of developing some inline technology to incorporate exposure into larger devices. It’s not practical for smaller machines yet. To accommodate the UV device into a small machine is difficult to accomplish, and would be costly. With larger machines it would be a considerably smaller percentage of the expense.
“Digital imaging solved the timing issue of main exposure, but it doesn’t eliminate the need for that piece of equipment,” Harrell notes.
Digital imaging is fast, he adds. “The fastest machines we have today will do a plate in 12 to 16 minutes. The intent was to get it so that it was not the slowest part of the process. Is it longer than exposing a piece of film? Sure, but the other benefits more than outweigh that. If someone is looking at digital imaging with a DuPont FAST processing system, they can go from RIP file to press-ready plate in 50 minutes.”
Europeans have adopted digital plate imaging more readily than those in North America, says Vic Stalam, GM/VP of packaging and thermal proofing at Kodak’s Graphic Communications Group. “But the US is catching up,” he says. “Among the issues that converters have with digital is that it requires a lot of investment, and it has to have a good ROI. So we need to make sure that we are taking steps out of the conventional process — labor and material costs — and speeding it up.”
The dot question
Opinions vary among everyone in the industry when the topic turns to comparison of dot structure and plate quality, digital vs. analog. Visitors to flexo bulletin boards online offer their thoughts: “It is not the digital plate, it is the total process that gives you the consistency.” “My experience is that digital plates wear out faster, especially in the highlights of the halftones, and you start getting the hard line at the end of vignettes.” “Digital plates last longer, there are faster setup times on press, and platemaking is easier — there are no ‘out of contact’ issues.”
Stalam explains one difference: “In the analog plate, with the film you are exposing light, you are bending light. With refracted light you will not get a sharp dot. With the laser you are getting no refraction and no light dispersion, and therefore you have a sharper dot. Not that one is better than the other, but different.”
Kodak markets its Thermoflex plate imagers in three sizes: narrow, mid-sized and wide. The systems also are capable of imaging offset plates.
“When we originally started,” says Esko’s Harrell, “we pushed quality as the strong benefit of digital imaging. That’s certainly a benefit, and we got good feedback on improved highlight dots and dot gain. But by and large almost every customer gave us positive feedback about consistency. It has taken what was historically very much a craft and made it a very reliable and consistent pushbutton process. And if we hear a negative on the consistency side, I’d be certain that it’s something solveable in the workflow.”
Esko also has several sizes of its Spark system, including a recently released narrow version. The company maintains that 80 percent of all digital plates produced worldwide are imaged on its systems.
“Another issue,” says Vic Stalam, “is registration between separations. With digital it is dead perfect every time. With analog you are still lining up separations. There is a slight chance that you won’t get perfect registration.”
Analog workflows, Bodwell adds, “are going away for reasons that don’t have to do with the plates. Imagesetters are going away: the machines are getting older; prices for graphic arts films are going up, and volumes are declining. Film processors themselves are getting old. The cost difference between a digital and an analog plate are still there, but they are shrinking.”
The FAST thermal processor, introduced initially at Drupa in 2000 and in its digital format in 2002 at CMM, has remained essentially the same, says Bodwell. “Well over 400 FAST units” are installed and operating in the US alone, he adds, and worldwide the number is 600. The basic machine is the 3547 (which processes material 35" x 47"). A new, larger version is the 4260.
MacDermid Printing Solutions, of Atlanta, GA, USA, a major supplier of photopolymer plates, also manufactures a thermal plate processing system which it calls Lava. DuPont recently filed a court challenge over the Lava system, but MacDermid says it is actively marketing its product in the flexo print market.
Total laser engraving
Last year at Labelexpo in Chicago, Stork Prints unveiled a machine that it calles the DLE — Digital Laser Engraver. The DLE is proclaimed as a one-step, perhaps two-step initially, plate production process.
“With a digital ablation system you are laser imaging the black mask, then exposing the plate in the traditional process, then removing the photopolymer in a FAST unit,” says John Costenoble, sales manager for Stork Prints USA, Charlotte, NC. “With the DLE you eliminate that, taking the digital art information and ablating directly into your plate material.” For the narrow web flexo market, the product is called the Helios.
“We are directly producing a 3D shape on a plate without imaging a mask,” says Ed James, Stork Prints’ product manager for graphics lasers. “No mask is used, there is no post exposure, no washout. We are directly creating a finished plate. All that is required is removal of dust or debris.”
Erik Jacob, the sales engineer for Stork Prints, says that the DLE allows the user to define parameters for plate creation. “It can be carved out any way that the user desires. They can use different profiles. Highlight dots can be different from full tone or midrange dots, in the same plate.”
“From the standpoint of operating systems,” notes James, “this does not mean a closed system. It can take software from virtually any front end system, as long as they have ability to output files in a tif format. It can take one-bit or eight-bit tifs (the preference is to take eight-bit tifs). It gives more control over profiling in the 3D sense and how dots are produced in the plate.”
The plate to be engraved in the Helios DLE must be exposed prior to engraving. “It requires a short back exposure and a longer surface exposure to make it stronger for the engraving process,” says Costenoble. The company is now working with suppliers to produce pre-exposed plates.
The investment in a Helios DLE can start at about $300,000. The machine also engraves Stork Rotascreens for rotary screen units, as well as flexo sleeves and embossing plates. With the additional tooling for the other processes the price can rise to $450,000.
The quest for better plates and processes will continue, and the newest technology is bound to thrill. But some basic questions should always be asked and answered, in the opinion of Anderson & Vreeland’s Joe Tuccitto.
“What does dot sharpening really do for you? Does it really increase the quality as much as people think? Is a round tip dot really better than a flat tip dot? I really don’t believe it is.
“If you can’t print with analog plates, switching to digital isn’t going to make your plates better. A lot of people had the mentality that digital plates would make printing better and easier. That’s not the case. If you are already printing well, digital will help you print sharper.”