Network Backbone Speeds Printing
Intense printing industry competition requires operators to have high quality, long-lasting control infrastructures with low latencies and high throughput. Computer Integrated Automation Inc. (CIA) uses CC-Link industrial network to provide the open backbone for controlling 32 Tensor web printing press units at Engle Printing & Publishing Co.
Intense printing industry competition requires operators to have high quality, long-lasting control infrastructures with low latencies and high throughput. Computer Integrated Automation Inc. (CIA) uses CC-Link industrial network to provide the open backbone for controlling 32 Tensor web printing press units at Engle Printing & Publishing Co. in Lancaster, PA. This network also controls two four-color web presses at Press Enterprise in Bloomsburg, PA.
CC-Link is used for remote interface, integrating third-party equipment, data collection, information handling, and the exchange of control signals between the control PLCs and the web offset printing presses.
Web printing process
Ink and water don't mix—that's the basic principle behind offset printing. When plates are exposed, an ink receptive area is activated for the image. Water, applied to the plate, adheres to the non-printing areas, and ink adheres to image areas. The image transfers from the plate to a blanket, which subsequently prints on paper. Offset printing presses are either sheet-fed or web .
Web press is a type of offset printing press that prints on continuous wide rolls of paper. It runs much faster than ordinary sheet-fed offset presses and delivers excellent quality. Web presses, because of high speeds, are generally used for very high volume printing, such as magazines, newspapers, catalogs, and long commercial runs. A web press can occupy several floors of a building and can consist of multiple interconnected four-color and single-color printing units, as well as a variety of sections to offer in-line finishing options: cutting, folding, and punching. Most web presses also print on both sides simultaneously, a feature not found on sheet-fed presses. These options make the web press a more complex machine than a sheet-fed press.
Before digital networking
CIA has been installing automated printing press lines since 1983. In those early days, every analog and digital I/O point traveled directly to the control cabinet in large unwieldy bundles. Years ago the amount of wiring in a 24-unit press typically ran 150,000 ft, and included hundreds of digital and analog I/O points requiring individual wiring to a central controller. With today's network technology, a 24-unit press can be installed with approximately 10,000 ft of wire, a savings greater than 90%, including cost of wire and labor to install, route, and terminate the wire.
Trying to install a printing press using advanced controls through a PLC with antiquated, non-networked I/O connections poses many problems. Challenges include interfacing the control cabinet workstations with terminals and serial cards, then bringing wire connections into each unit. Start-ups can be long when they must include tracing back every wire, rechecking every terminal connection, and setting programmable destinations to the correct receiver. Some third-party equipment devices are difficult to wire to a master controller, complicating overall design. Once completed, numerous problems can persist with this type of non-networked installation. Operational latency issues are cumbersome, and tracking down performance bottlenecks can prove to be complex.
Use of the CC-Link network at Engle Printing & Publishing achieved substantial cost savings, both from what the network provided and what it eliminated. CC-Link reduced the amount of wire needed by more than 92% compared with the prior hard-wired connections.
The original installation consisted of 24 units (four four-color presses and eight one-color presses) capable of 45,000 impressions per hour. The company added eight more press units after the initial installation. Digital network technologies allowed CIA to start the new units off site (it's based in Carol Stream, IL) through a modem connection, saving an estimated $25,000.
Electrical and installation project savings totaled approximately $100,000. Fewer wires required termination in the main control cabinets, so enclosures became less crowded and troubleshooting became easier. Moreover, startup time of the press line dropped to three days (including operator training) from an average of 14 to 21 days (without training).
Digital network accuracy, speed, and durability provided conditions that reduced paper waste, offered safer operating conditions, and reduced damage to the press units and folders due to paper wrap-ups. This increases equipment longevity while reducing routine service and maintenance. Prior control architectures didn't offer these benefits.
CIA can remotely interrogate the control system to determine if a service call is necessary and whether the problem is mechanical or electrical in nature, allowing experts to direct Engle personnel. Remote capability allows CIA to retrieve parameters and fault warnings inside the vector-controlled, variable-frequency drives (VFDs) and to make changes via modem into the drives. Older technology required more attention, service, and maintenance. On-site additions, deletions, or changes were impractical with non-networked presses. Print quality also has improved.
Many brand name third-party equipment devices can connect to the open, standard CC-Link network and integrate into the overall control scheme. The press installation at Engle Printing & Publishing used automation equipment from many manufacturers, including Mitsubishi Electric PLCs, Mitsubishi digital and analog I/O connections, Mitsubishi motion controllers, Festo pneumatic valves, Mitsubishi VFDs, and Wago digital and analog I/O modules.
CC-Link network speed (10 Mbps) and 5-ms update time of the networked analog and digital I/O modules allowed for quick response in the control of the ink and water motors. This reduces paper waste that would occur during start-up and after plate changes. Fast network speed enables faster system response in the event of a web break or a paper jam. These benefits were unavailable with a non-networked system.
The project was delivered with a shorter start-up time, within budget. It has less down time and integrates all equipment into one master control scheme.
Chuck Lukasik is director, CC-Link Partner Association-North America.
Network advantages: modular, digital
Tensor T400B press units are designed with a separate CC-Link network for each unit for a modular, expandable design concept. Each press unit produces one color.
Network feature allows separate startup of each unit (and each color). This can be scheduled by the end-user when convenient and can be done remotely.
Modular designs ease onsite expansions. Units can be stacked four high, rather than along side each other, saving space. Each press unit has two control panels.