Printing Impressions

You will be automatically redirected to piworld in 20 seconds.
Skip this advertisement.

Advertisement
Open Enrollment | Subscribe to Printing Impressions HERE
Connect
Follow us on
Advertisement
 

DAMPENING SYSTEMS -- Striking a Balance

September 2003
BY MARK SMITH


Heavy iron, a moniker for presses that conveys size and brute force, has been supplanted by talk of electronic controls, digital integration and computerization. Lest anyone forget, the real magic of lithography still happens when ink and water (fountain solution, to be precise) meet on the plate.

Mechanical systems are what make a press, even if an increasingly more electronic face is being put on them. None play a more central role in the offset printing process than the dampening system. The fundamentals are the same for web and sheetfed press applications, but the solutions of choice tend to differ.

Delta dampening is the de facto quality standard for half- and full-size sheetfed presses, asserts Michael Barisonek, vice president of sales and marketing at Epic Products International in Arlington, TX. To date, the web market hasn't had the same quality demands, even for heatset work, as the sheetfed segment, Barisonek adds. "That is changing, though."

Spray dampening is considered by proponents to be the current standard-bearer for web applications. Advancements in spray dampening controls, valves and precision nozzles have made spray systems suitable for printing on coated stock with a higher level of quality than ever before, asserts Dennis Schupp, vice president of operations at Smith RPM Corp. in Lenexa, KS. The manufacturer's spray dampening systems are sold by Pressroom Products in the United States.

"Water spotting, pulse marking and striping—which all previously were quality issues with spray dampeners—have been eliminated in today's high-speed, digital pulsed systems," Schupp says.

Baldwin Technology, based in Shelton, CT, put together a position paper to make its case for spray dampening on web presses. A key benefit of the technology, it argues, is a reduction of performance variances.

Getting Stable

"Spray dampening technology is designed to reduce and, if possible, eliminate sources of change, thereby stabilizing the process and improving both quality and productivity," the piece notes. For the most part, this is accomplished by simply eliminating mechanical parts. Delivery of fountain solution using a spray mechanism can do away with brush and pan roller systems (rollers, motors and gearbox), belts, pulleys and bearings, for example, the company points out.

According to the manufacturer, pressroom temperature is another variance factor and can impact the amount of water delivered by open dampening systems, which rely on surface tension for transfer. Similarly, contamination is of particular concern with brush dampening systems, the position paper continues. Ink-matted bristles will not transfer water properly, so the operators start cleaning the brushes with blanket wash, which winds up in the fountain solution and can lead to scum, toning and tint problems.

On a web press, switching to a new spray dampening system can improve print quality by reducing dot gain, boosting contrast, producing better gloss and providing a more consistent ink density, the manufacturer says. Time savings come from faster makeready and setup, combined with reduced downtime and maintenance requirements, it adds.

Dallas-based Accel Graphic Systems offers dampening systems designed for smaller format sheetfed offset presses. The nature of that market means that tradeoffs between press features and costs usually have to be made. Therefore, advances in technology have made new and existing presses prime candidates for upgrading to continuous dampening systems, points out Lance Carpenter, Accel's general manager.

For this segment of the industry in particular, the press operator's skill level can be a factor in choosing the right dampening system, Carpenter asserts. "The simpler the system is to operate, the easier it is to increase the quality of printing and produce profits," he says.

"System" is an operative word in the discussion, says Thomas Haas, vice president of technology at technotrans america, sheetfed division, in Corona, CA. "Effective control starts with the incoming water supply and encompasses the proper dosing of the fountain solution and additives, proper mixing of the solution after dosing, temperature control, rate of water flow/exchange and filtration, to name a few issues," he argues.

Many presses still use fountain solution circulation systems with 1960s-era designs, Haas says. "Most older sheetfed and web presses were installed with simple, single-tank recirculation units that provided cooling of the water, as well as circulation to and from the press water pans, along with very basic and fairly inefficient filtration," he points out. Thus, printers stand to benefit by upgrading from this technology.

Getting back to the discussion of Delta dampening, Epic's Barisonek points out that it is a licensed technology, as well as a product. "The key to the technology is the differential, or Delta, speed between the form roller and the plate cylinder. Delta is a scientific notation for a difference," he explains.

The speed differential enables the dampening form roller to dislodge particles from the plate that otherwise would cause hickeys, the company exec adds. "It also allows the plate to run with less water, so you get less dot gain and sharper print."

Epic can lay claim to having invented the technology and continues to pursue its further development, Barisonek says. Major press manufacturers license the company's patent and build their own dampening systems with the "Delta" feature, he adds. A licensee isn't required to include Delta in the product name, but can elect to do so.

The company also offers its own Epic Delta dampening systems as retrofits for presses that don't currently have the capability. Building on its success with high-end sheetfed presses, Barisonek believes the technology also can be suited to web and small-format sheeted applications. The added cost can be offset by paper savings, waste reduction and greater utilization of available press time, he says.

Eliminating hickeys is Delta technology's claim to fame, but not its only benefit, Barisonek contends. Epic Delta dampening systems reduce the number of makeready sheets required because the press comes up to color faster, he says. "Color variation also is reduced during the run for two reasons: you are using less water to get into balance and you don't have to start and stop for hickeys."

Kompac, a division of Day International, sees waste reduction as such a key benefit of its dampening systems that it guarantees they'll reduce waste by at least 50 percent. It also promises to add 30 to 60 minutes of press production per day.

The manufacturer offers a family of Kompac-branded automatic dampening systems, with models for small sheetfeds up to large web presses. The units are said to provide automatic ink/water balance.

The process is started by holding fountain solution in the nip reservoir between the form roller and metering roller. The form roller then rolls across the plate with the non-image area of the plate taking fountain solution (water) and the image area splitting a layer of ink with the form roller, since it is both water and ink receptive. Ink and fountain solution are milled under pressure at the roller nip. The dampening systems are said to "rebalance" themselves, since surplus fountain solution is returned to the nip reservoir with each revolution of the plate cylinder.

Kompac also believes in the systems approach, having just launched a new line of fountain control systems. The eight-gallon, non-refrigerated and 16-gallon, refrigerated circulators feature continuous circulation and filtration. Both reportedly ensure a constant supply of fresh fountain solution to the dampening system.

technotrans pioneered the development of combination fluid and temperature management systems, Haas says. It currently offers two product lines: alpha.c (standard) and beta.c (premium). The systems provide cooling for the ink rollers in single- or multiple-zone formats, and enable central management of the fountain solution for all print units. Standard features include dosing of two additives, premixing of the dosed solutions, conductivity monitoring, automatic level (replenishment) control, power drain and stage filtration.

Haas believes there still is a place for single-tank units, as well. They can, for example, be used in conjunction with a combination unit when running an especially problematic color, he contends.

Baldwin's LithoSpray dampener features a circulator system (DailyLiner) that filters, regulates the temperature and controls the dosages of etch. It uses high-pressure pumps to push water through a regulator and filter into the water-feed manifold, which contains its own screen filter. These components are said to assure delivery of clean, cooled and properly dosed fountain solution.

The system's computer controls are programmable and enable the solenoid to be regulated in thousandths of a second. Four programmable curves are tailored to the paper stocks run by a shop. Functions can be selectively performed by an individual head, the whole bar, a whole unit (upper and lower) or the entire press.

Smith RPM's pulsed dampeners offer automatic flood control for fast makeready, zone control to easily adjust water across the cylinder and clean, closed-loop fountain solution circulation, Shupp says. The TouchStar model is user-friendly and easily programmed to track press speeds, with the flexibility to adjustment for non-linear curve tracking with ink, he adds.

Its patented flow-through design is said to maintain a consistent, fresh flow of fountain solution to the plate. Independent nozzle pulsation provides overlap control and precision adjustment for higher quality printing. TouchStar II digital controls incorporate chemical-resistant touchpads and LED readouts for maximum visibility.

Accel Graphic Systems offers the Crestline continuous feed dampener, which is designed for small offset presses. The system reportedly provides instant ink and water balance, and installs quickly without altering the press. It is designed to provide an uninterrupted flow of fountain solution to the plate, run alcohol-free and reduce paper waste by up to 50 percent, according to the manufacturer.

Crestline dampeners are easy to use and include single-lever control, gear-driven operation, ball bearing construction and a water tray that is easy to remove, Carpenter says. Most Crestline systems can be installed in less than one hour, he adds.

Townsend Industries also offers a solution for the small sheetfed market in the form of a continuous dampening system for S-1 models of its T-51 self-contained, independent printing units. It is available for presses from A.B.Dick, Multigraphics and Ryobi/Itek.
 

COMMENTS

Click here to leave a comment...
Comment *
Most Recent Comments: