A digital printing system, whether it's a desktop unit, a black-and-white copier/printer, a production color copier or a digital press, has two main components: the print engine and the print controller. The engine and the controller are often developed and manufactured separately, and later integrated into the final product. The print controller is responsible for interfacing with a host system and handling communications via the interface. It also interprets print commands coming from the host and translates them into the signals required to drive the print engine. At its most advanced level, the controller is the conductor of the orchestra: Machine functions ranging from duplexing to color management all depend on it.

　　Entry-level digital printing systems often feature embedded controllers, hidden inside the printer case. Further up the food chain, controllers tend to be more sophisticated, expensive and larger. External controllers are essentially high-end workstations and PCs dedicated to performing a variety of tasks for the print engine. They often come with full-blown operating systems (OSs), monitors and keyboards, and are alternately referred to as the RIP or server.

　　Throughout the past few years, the demands on print controllers have increased. Users are asking for more PCL or PDL support for cross-platform environments, faster processing speeds, more communication options, higher resolutions, high-quality color, more memory, and variable-data personalization and multifunction capabilities. Taking advantage of recent print engines' increased functionality also requires more powerful controllers.

　　In response, vendors have developed print controllers based on distributed on-board processing, where each processor is dedicated to a particular function and communicates this information to a core processor. Application-specific integrated circuits (ASICs), designed for certain functions, use existing circuits as basic building blocks. A print controller might have one processor dedicated to communication interfaces, one dedicated to memory management, another for graphic processing and one for data processing.

　　COLOR COPIER, PRINTER CONTROLLERS

　　The color-copier-controller market has significantly consolidated. In 1997, Splash purchased Quintar and ColorAge, and in 2000 was acquired by Electronics for Imaging (EFI) (Foster City, CA). Prior to acquiring Splash, EFI had purchased Management Graphics in 1999. In 2001, Colorbus was purchased by Color Print Solutions (Anaheim, CA), while Imation announced the sale of its color business unit to KPG (Norwalk, CT). High-end vendors have also consolidated. Global Graphics (Cambridge, England) acquired Harlequin in 1999, while Barco Graphics and Purup Eskofot merged their operations to become Esko-Graphics (Gent, Belgium).

　　EFI accounts for roughly 90 percent of the installed controller base. Although color-copier and printer vendors will likely continue to rebrand EFI controllers, we anticipate more in-house development as vendors try to increase their profit margins, reduce the system prices and differentiate their products by developing their own controllers.

　　Both EFI and Creo (Billerica, MA) are currently vying for control of Printcafe — see story on p. 10.

　　BLACK-AND-WHITE SYSTEM CONTROLLERS

　　High-volume, black-and-white, non-impact systems have been used for transactional printing for more than 20 years, and for on-demand publishing for more than a decade. Controllers have evolved from proprietary, standalone devices to powerful server platforms running under common OSs.

　　Today, one common print engine can serve both transactional and publishing requirements. Vendors have upgraded their controllers, enabling users to merge their transactional and on-demand product lines. Some vendors are also reconfiguring their monochrome controllers to support color systems.

　　The base configurations of the Heidelberg (Kennesaw, GA) Digimaster 9110 and 9150 cut-sheet systems use controllers running under the Sun Solaris OS. The standard subsystem includes a Web server, high-performance RIP and Heidelberg's PDF-based ImageSmart production software. Heidelberg provides additional data-stream support with the DataXceed server, which enables Heidelberg customers to run transactional and on-demand applications from one environment. DataXceed supports Heidelberg's color and monochrome digital products.

　　IBM Printing Systems' (Boulder, CO) Infoprint 2000 is based on the Heidelberg Digimaster 9110. IBM offers two models: AF1 and MS1. The AF1 advanced function printer is targeted at data centers and serves as a network or channel-attached production printer supporting IPDS via IBM's Advanced Function Common Control Unit (AFCCU). The MS1 system printer can be configured as a high-speed duplicator and/or as a production printer when network- or channel-attached to a host delivering HP PCL 5/6, Adobe PostScript 3 or Xerox LCDS/Metacode data streams. It is targeted at publishing applications and OSs that have both on-demand and transactional printing applications. IBM's AFCCU also drives the web-fed Infoprint 4100.

　　Océ Printing Systems' (Boca Raton, FL) VarioStream (continuous-feed) and VarioPrint (cut-sheet) systems offer customizable processor speed, memory, image quality and throughput. The Océ SRA2 controller architecture includes support for publishing and print-on-demand languages, including PostScript 3, PCL 4, PCL 5e, TIFF and PDF, as well as transactional languages including AFPDS, IPDS, LCDS and Metacode. The SRA2 controller also supports 240-, 300- and 600-dpi resolutions. All Océ VarioStream and VarioPrint models can be driven from Prisma workflow software, which includes the Adobe-based Unity RIP and connectivity to Xerox DigiPath.

　　Xerox Corp.'s (Rochester, NY) Document Services Platform (DocuSP) runs on the Sun Solaris operating system and drives Xerox monochrome and color printers in on-demand, publishing and transactional printing environments. Beginning with version 3.6 (released in 2002), DocuSP provides native support for Xerox LCDS, IBM IPDS, HP PCL, PostScript, PDF, ASCII and TIFF. With the DocuSP controller platform, Xerox can offer EPS versions of its DocuTech and DocuPrint systems that serve transactional and on-demand printing and publishing requirements. EPS versions of the DocuTech 6100, 6115, 6135, 6155 and 6180 are available. The Xerox continuous-feed product line provides native IPDS support and up to two host connections per print engine: IBM TCP/IP Ethernet 10/100 Base T or IBM IPDS Channel S/370. Data-stream support can be extended with an optional connection to the DocuSP platform.

　　Delphax Technologies, Inc.'s (Minneapolis) CR Series of continuous-feed EBI printers is available in models targeted at publishing (“P”) and transactional (“T”) environments. “P” models support PostScript, PCL and PDF; “T” models support Xerox Metacode, LCDS and IBM AFPDS. T models provide bus and tag, as well as network (TCP/IP) support, while P models provide only network connectivity. Delphax has turned to AHT (El Segundo, CA) to develop a print server to drive the Delphax CR and Imaggia systems. The Unify Delphax HV printer server will be based on the AHT Unify server platform.

　　Nipson America, Inc. (Elk Grove Village, IL) offers two product lines of monochrome magnetographic printers: the VaryPress series, suitable for commercial-printing applications, and the 7000/8000 series for data-center and in-plant environments. The Nipson IntelliStream controller runs under a Windows NT Server and delivers high-throughput performance on variable-data jobs through off-line rasterization. The Nipson OpenPage print server runs under AIX, SCO Unix or Windows NT, and the OpenPage Print Station runs under Windows NT. The OpenPage Print Station PostScript interpreter supports Levels 2 and 3, PDF, EPS and TIFF, while the PCL interpreter supports HP PCL 5e.

　　CONTROLLING HIGH-SPEEd VARIABLE COLOR

　　Although many digital presses are used for static, short-run color printing, the controller must also be able to handle full-color, variable-data printing at speeds of 100 ppm for electrophotographic engines, and significantly higher for inkjet presses.

　　Necessity drove many vendors to develop proprietary print languages and architectures. Recently, however, many vendors have joined the effort to establish PPML as a vendor-neutral XML-based markup language. PPML, when implemented on a digital-press controller, enables users and software developers to avoid creating platform-specific solutions. Also, more vendors have implemented PostScript Extreme architecture, enabling them to offer more easily scaleable controllers.

　　Heidelberg's NexPress 2100 color digital press is driven by the NexStation digital front end running on a Windows NT platform and using Adobe Extreme architecture. It features full Adobe PDF/Portable Job Ticket Format (PJTF) implementation and supports PPML/VDX variable-data input. NexPert Systems, a range of software tools and Internet-based services for the NexPress, includes various productivity-enhancing controller options. The NexPert operator support system provides users with quick machine recovery without outside help. According to NexPress, 65 percent to 75 percent of all machine problems can be solved on-site by an operator using the NexPert System.

　　HP Indigo (Palo Alto, CA) digital presses are driven by Intel Pentium processors running under Windows NT. Recent HP Indigo machines store jobs in a fast 36-GB virtual memory RAID disk array instead of the RAM-based system used in the original Indigo e-Print 1000+, resulting in faster processing. HP Indigo controllers support Adobe PostScript 3.

　　The company offers two approaches to variable- data printing. Swift Native Accelerated Personalization (SNAP) is an efficient variable-data solution that is specific to HP Indigo presses. The company sells PC and Mac-based QuarkXPress extensions to emit the appropriate data stream. Whenever possible, SNAP avoids rasterizing objects more than once, and often avoids the PostScript RIP altogether. HP Indigo presses also support PPML.

　　Maximum throughput

　　The IBM Infoprint Color 130 Plus digital press is driven by the IBM Advanced Function Common Control Unit (AFCCU), a native IPDS controller that enables object caching and parallel page processing. The Infoprint Color 130 Plus can output full-color documents created in AFP (with full page-level error recovery), PostScript 3 and PDF.

　　Prior to its acquisition by Punch International NV (St-Martens-Latem, Belgium) in 2002, Xeikon offered two front ends for its color digital presses. The eXpert digital front end is based on the Barco PrintStreamer 2 and uses a Harlequin ScriptWorks software RIP; the IntelliStream controller was included with Xeikon's acquisition of the Agfa ChromaPress business in 2000.

　　The Barco PrintStreamer is a high-speed print buffer that sits between the Barco Graphics FastRIP/X and the Xeikon digital press. Barco has shipped more than 1,000 PrintStreamer front ends for Xeikon-based digital presses since the introduction of the product in 1994. The IntelliStream controller — the second Xeikon front-end solution — consists of hardware, software and patented compression technology to maximize throughput and increase productivity. It incorporates an Adobe PostScript 3 CPSI and supports PPML. After its acquisition by Punch International, Xeikon indicated it would no longer market the Barco front end.

　　Xerox offers a variety of controllers for its DocuColor 2000 Series. Creo Spire controllers use an NT platform and are targeted at commercial printers requiring support for multiple variable-data print languages, including Xerox VIPP, Creo VPS and PPML. EFI controllers for the 2000 Series support PPML and VIPP. Xerox's own DocuSP controller runs under a Unix platform and is targeted at customers who may desire a DocuTech workflow. The company also offers a Series 2000 controller that supports IPDS and legacy data streams. The Xerox iGen3 is available with Creo and DocuSP controllers.

　　Controller alphabet soup

·         Advanced Function Presentation (AFP) refers to IBM Printing Systems' (Boulder, CO) multipurpose architecture that provides interface and command capability for a wide variety of functions. It is most commonly used in corporate data centers and encompasses document creation, formatting, archiving, viewing, distributing and printing. Think of AFP as an environment rather than a product.

·         Intelligent Printer Data Stream (IPDS) is the device-specific print stream created by the AFP print driver. IPDS can be processed natively or transformed via software into a format supported by the printer.

·         Line Conditioned Data Stream (LCDS) is a line data stream used to drive Xerox Corp.'s (Rochester, NY) production printers from host systems. Unlike page description languages, which create pages from high-level graphical constructs, print command languages such as LCDS contain printer commands interspersed with data and are processed and executed sequentially.

·         Metacode is an ASCII-based print command language used to drive some Xerox publishing systems (see LCDS).

·         Print Command Language (PCL) was developed by Hewlett-Packard (HP) (Palo Alto, CA). Initially PCL was a device-specific language that used escape codes to send instructions directly to a printer at a specific resolution. HP introduced support for scaleable fonts in PCL 5, and device-independent features in PCL 6, bringing it closer in function to PostScript.

·         PostScript is a device-independent programming language developed by Adobe Systems Inc. (San Jose, CA) to drive digital printers and displays.

·         Portable Document Format (PDF) was developed by Adobe Systems as a platform-independent means of rendering documents for viewing and printing. PostScript is an imaging model implemented via a programming language — PDF is simpler and more structured. A print controller that can process native PDF files is thus more efficient than one that requires PDF to be converted into PostScript first.

·         Tag Image File Format (TIFF) is a file interchange format for raster images.

　　Tips for choosing a controller

　　When shopping for an entry-level digital printing system, controller options are usually reflected in different printer models: One model may offer special connectivity features, while another supports special paper handling or command languages. Production systems use external controllers, or print servers, and may offer some latitude among brands and features. Here are a few general rules of thumb:

·         Be sure to think upstream and coordinate the controller with your applications or the types of files customers will be sending. Does your application support the print languages supported by the controller? How are your customers submitting jobs, especially long runs that may involve thousands of records? This is especially critical in choosing a printing system and controller for variable-data applications where the data may need to be packaged and sent to the printer in a very specific manner.

·         More RAM generally equates to faster throughput and a higher price tag. When in doubt, choose a controller with more RAM, rather than less, since your printer is no faster than the controller.

·         Beware of blanket claims, such as “we support PPML.” PPML can be implemented in vastly different ways on a controller. Running tests with live data is the only way to evaluate support and functionality.

·         Be highly suspicious of software that claims to transform one format, such as PostScript, into another — such as IPDS. Like support for PPML, transformations can be done in many different ways. PostScript, for instance, may be converted into raster images to drive a native IPDS printer — this will work, but will probably be very inefficient. When in doubt, test again with live data in real-world scenarios. Your printer will always run faster in native mode.

·         Although standards are generally good for products, “proprietary” isn't necessarily a bad word. Though a print language may be specific to one manufacturer, it likely runs smoothly and efficiently.

　　Don't buy any controller based on features that aren't available until the next release. If functions aren't present and working today, don't count on them being there tomorrow.

[时间：2003-11-17  作者：Bisenet  来源：Bisenet]