Computer-to-Plate Systems: Imaging with heat and light

Computer-to-plate (CTP) systems have been central to the process of moving traditional offset printing into the digital age. CTP is the ability to output text and images directly from a digital file to press plate material, completely eliminating the time-consuming and often highly specialized prepress work of creating film images, stripping them into flats, and then burning plates. By simplifying platemaking, CTP has helped to make full-colour work easier to produce, and this in turn has increased customer demand for colour. With CTP, smaller shops that ten years ago might have printed primarily one- and two-colour jobs with simple graphics now can produce process-colour work and sophisticated images quickly and profitably.

Before investing in a CTP system, printers need to evaluate their existing production procedures, taking into account what types of work they do, what types of work they want to do, and their plans for growth. This is particularly true for printing companies that do primarily small to mid-size format work, where other options, such as multicolour or full-colour digital printing or variable data printing, might be a better fit in their overall operation.

Direct imaging (DI) presses present yet another alternative, combining direct-to-plate capabilities with more or less traditional offset printing. The type of equipment to purchase depends entirely on what direction a printer wants to go. CTP systems create plates very accurately and relatively easily for static, printed pages produced in volume for every kind of application, from marketing materials to packaging.

Printers looking to either add CTP or to upgrade an existing system will find an array of products available. Some systems, such as Glunz-Jensen’s iCTP PlateWriters and Xante’s Impressia and Speedsetter systems, are lower-cost systems that provide the direct-to-plate advantages of time and cost savings, but without the wider range of features or the expandability that are built into the higher-end models like those from Agfa or Fuji. Another key consideration is the total cost of operation, including the initial investment for the system itself plus ongoing expenses for consumables like plates and chemistry, if required. And, where plates must be chemically processed, waste disposal and environmental issues also come into play.

Smaller format devices

Glunz-Jensen’s iCTP PlateWriter models are slightly different from most CTP systems in their use of ink jet technology. Where most CTP technologies use light or heat to image the surface of a plate, the iCTP models jet their patented Liquid DOT chemistry onto non-photosensitive aluminum plates. The non-image area of the plate is then gummed in the integrated plate finishing unit. The manufacturer says there is no need for any special lighting when handling the plates and no further processing is required. Glunz-Jensen’s newest model is the iCTP PlateWriter 2000, a 2-up plate system in a product line that also includes the 4-up PlateWriter 4200. Throughput speeds depend upon the size of the plate and imaged areas, and on the 4200 model, users can select fast, high-quality, or super high-definition modes. Both models employ a RIP based on Harlequin technology with imposition and trapping software options available. The PlateWriters can be used with either Mac or PC platforms.

Xanté offers two metal plate setters for the 2-up format, the Impressia with a maximum 13.38”x19.87” plate size, and the Impressia GTO with maximum 16.5”x25” plate size. Both systems employ an Adobe PDF-based RIP and Xanté’s Aspen proprietary non-photosensitive metal plates, which require no processing or washing and can be handled in daylight. Xanté says both units use the company’s Z-7 imaging technology and expose the plate material using radiant energy. The Impressia models produce a 2400 x 2400 dpi resolution, with 100 lines per inch.

For use with polyester plate material, Xanté has the SpeedSetter CTP system in both portrait and landscape models. Both produce screen resolutions to 4000 dpi and 240 lpi and use a PDF-based RIP. The model 300iL offers a maximum plate size of 13.3”x20”, and the 400iL has a maximum plate size of 15.75”x20.25”. The SpeedSetters use red-sensitive polyester plates, and come with a plate processing unit that can be moved away from the imaging device for maintenance.

Presstek is one of the earliest developers of CTP and DI systems, and currently focuses on the small format 2-up and 4-up market. The VectorTX52 produces 16 plates per hour in sizes up to 20”x21”, at resolution of 2400 dpi. The system uses Presstek’s Freedom plates, which the company describes as having the stability of metal plates, but the economical pricing of polyester plates. They require no processing or gumming, only a pass through a plate washer that’s integrated with the VectorTX52. Freedom plates can be used for print runs up to 25,000.

The larger Dimension Excel is offered in two models: the Dimension225/250-AL Excel with a maximum plate size of 22”x22”, and the Dimension425/450-AL Excel, with a maximum plate size of 26.7”x30.7”. Both employ Presstek’s ProFire thermal imaging technology for resolution of 2450 dpi, and both use the company’s Anthem Pro plates, which are daylight safe, chemistry-free, and require no gumming or baking.

Heat vs. light

Apart from Glunz-Jensen’s inkjet process, most CTP devices employ either violet light or thermal heat to expose plate materials. Both technologies have advantages and disadvantages, and there is a continuing debate in the industry about which is better.

Tony Karg, Senior Director of Business Development for Fujifilm Canada, says, “Thermal uses a thermal laser diode, so essentially you have a laser that heats the surface of the plate to expose it. The other type of technology is the same type of violet laser that reads the surface of a DVD. Violet CTP has the advantage of being a typically lower cost device, [which is] lower [in] cost to operate over the life cycle of the device. The engines are cheaper because of the types of components in them, and they’re cheaper to replace.”

“The key advantage of violet is obviously lower service costs,” he continues. “The second thing is that their photopolymer plates are actually more suitable for UV applications. They have a lot better run length characteristics, but in the small format market, that may not be applicable.”

Violet plates are aluminum-based with a surface treated with photopolymers. They usually must be handled in yellow light, and for most, the non-imaged surface has to be chemically washed out before the plates are mounted on the press, though Karg states that Fujifilm will be introducing chemistry-free violet plates in the near future. By contrast, thermal plates, also aluminum-based, can be used in daylight, are chemistry-free, and require no processing beyond perhaps a water rinse. Thermal plates also are available from many more suppliers than violet plates and in a wider variety, in terms what types of processing they need.

Fujifilm Canada offers both violet and thermal CTP systems in a range of sizes and configurations. “The reality is,” Karg says, “in the Canadian marketplace, thermal has got about 80% market share. You’d probably want to stick with thermal because there just aren’t a lot of violet devices out there.”

Karg recommends Fujifilm’s recently-introduced Dart system as an entry-level CTP system, or for printers who do high-quality work in smaller, 4-up formats. Dart is available in both thermal and violet (Luxel T-6000) versions, and offers a 32-21/32”x26” plate size. The thermal DartE produces 10 plates
per hour at 2400 dpi, and the Dart III—also thermal—is twice as fast at that resolution, and provides six levels of resolution, up to 4000 dpi. Dart comes bundled with workflow software to cover almost any type of application, and it can be tailored to suit the needs of the CTP system and the particular printer.

Karg also notes that Fujifilm Canada is the only manufacturer of CTP systems that provide sales and support from local offices across Canada.

Another major manufacturer in this field, Agfa, also makes and markets both thermal and violet systems for almost every conceivable printing application and for a range of plate sizes. Agfa’s Avalon SF model is designed for 4-up formats and uses thermal technology. Violet is offered in only the Avalon LF 8-up model. An autoloading cassette pre-punches plates before they’re loaded, punching one plate while another is imaging to improve throughput for volume plate production. In addition, the Avalon Plate Manager can handle up to four cassettes to keep the system in continuous operation.

A high-end system, Avalon features an HD imaging head, dynamic autofocus that continually monitors things like plate thickness for variations, automatic calibration, and remote diagnostics. Agfa also provides a wide range of plate materials for use with its own hardware and that from other manufacturers. These include visible-light plates based on silver or photopolymer technology for use in violet or thermal CTP devices. Agfa’s thermal plates include both conventionally processed plates and ThermoFuse plates with chemistry-free processing. In addition, Agfa’s Apogee and Apogee PrintDrive workflow systems offer a full spectrum of capabilities for volume and high-quality print production.

For future growth

Dainippon Screen, and its North American subsidiary ScreenUSA, manufactures CTP systems under its own brand as well as serving as an OEM supplier to other manufacturers. The company claims to have more CTP installations globally than any other, and its PlateRite product line includes equipment that goes from 2-up to 36-up formats. Mark Crawford, Screen’s Product Manager for CTP, says that the PlateRite models 4300E and 4300S are most applicable for small-format work, producing plates from 12” x14.6” to 32.7”x26”. A thermal CTP system, the 4300 can use thermal plate materials from a variety of manufacturers.

“Worldwide, we probably have 50 plates certified on our devices,” Crawford says. “We’re not a plate manufacturer. We’re a high-precision manufacturing company. So the PlateRite gives you the ability to buy best-of-class hardware, and then you can make your best deal for the plates.”

Crawford notes that demand for the small-format CTP system comes both from smaller print shops and from large printing companies that run small-format presses. The 4300 systems accommodate both, and a basic 4300E system can be upgraded to a 4300S by installing an additional set of diodes. Screen’s Trueflow software also can be tailored to the needs of each customer.

“We believe you should install workflow that will grow as you grow,” Crawford says. “You can start with RIPping and trapping, move to inline imposition, go to JDF, automate some things, can go to true automation with soft proofing, transfer of data across Internet. We can start you out basic then move you up the pyramid as you grow.” Software modules can be licensed for 90-day trials.

“Once CTP is set up, it’s more or less like a laser printer. Our machines self-calibrate, so there’s nothing for the users to do,” he says, adding that that’s as it should be, because “frankly, printers don’t make money in prepress.”

More choices

This survey wouldn’t be complete without two more key players in the CTP area. Press manufacturer Heidelberg offers a full line of CTP systems with a full complement of features and options, including the thermal Suprasetter A105, which was designed as an entry-level system. The Suprasetter A105 has a maximum plate size of 27.5”x41.3” and can produce plates for both sheetfed and web presses at the rate of between eight and 15 per hour, depending upon plate size. For printers with Heidelberg presses, the Suprasetter integrates with the Prinect workflow and offers a range of time and labor-saving features. These include manual, semi-automatic, and fully automatic plate production, multiple plate cassette management for continuous production, an internal plate punching system, and debris removal, which Heidelberg says allows the Suprasetter A105 to use processless thermal plates.

Finally, Kodak Graphic Communications several years ago acquired Creo Inc., a pioneer in CTP systems, and now has a complete CTP product line that incorporates technologies such as patented SquareSpot imaging. The Magnus 400 and Magnus 400 Quantum CTP systems provide a 4-up plate size (maximum 26.14”x29.5”). The Magnus 400 is semi-automatic and produces 16 plates per hour at 2400 dpi resolution, though resolution can go to 3048 dpi and a 120-line screen. The Quantum system produces 28 plates per hour at 2400 dpi, with a maximum resolution of 2540 dpi and a 100-line screen. Both have Staccato screening capabilities as well. Magnum systems can use Kodak’s Prinergy, Prinergy Evo, PS/M, or Brisque workflow solutions, or can connect to third-party workflow software. Kodak recommends the use of its Thermal Direct non-processing plates, but the Magnums also accept chemistry-free and other processless plate materials.

Any serious shopper for CTP systems will find even more manufacturers and suppliers than the eight listed here, and products that provide varying balances of productivity and image quality, and range from simple operation to a wide range of software and hardware features serving any number of specific applications.

The best place to start planning your CTP installation or upgrade is inside your shop. Determine exactly how much capability you need right now, as well as what may be needed several years down the road.