Competitive Edges

Digital's descent on web guiding continues, but converters also see value in tried-and-true approaches.

by Susan Friedman

Digital this and digital that. In package printing equipment, it's nearly impossible to avoid. Web guiding technology is no exception, though many converters are just now beginning to buy into their digital story—one that has been told for several years.

BST PRO MARK has produced digital signal controllers, complete with internal networking capabilities and a flexible module bus system, for more than 10 years.

The company's web guide expertise also includes ultrasonics, infrared, and CCD camera sensors, as well as pneumatic edge and servo-controlled sensor positioning.

From this wide-ranging perspective, Web Guide Product Manager Steve Hrycko sees "tons of the tried-and-true" out there. Converters like "safe, stable" options such as ultrasonic and infrared sensors; they don't want to worry about web guides beyond that, he adds.

In simplest terms, any "electric" guiding system is analog, while a "digital" system contains a microprocessor or computer to perform its functions, clarifies Eddie Engledow, web guide product manager at Fife.

If digital web guides are indeed what is desired, package printers need to determine how far they want microprocessor power to extend. Analog infrared or ultrasonic sensors might have digital controllers, while a digital camera-based sensor might have electrical controls.

Erhartdt+Leimer digital guiding systems now include digital sensors and digital controls, says Don Ross, V.P. sales and marketing.

An example is E+L's new FE-5001 CCD chip camera color line sensor for slitter/rewinder applications, which is connected to a digital control system via a CAN bus interface. The FE-5001 guides webs from edges, lines, broken lines, or print repeats, the latter of which eliminates the need for a guide line, reducing web widths for material savings.

Ross expects digital camera technology to become more pervasive in web guides, mainly to provide a greater variety of information. Broadened use of camera technology can also eliminate moving parts from guide systems, and thereby additional opportunities for inaccuracies, he explains.

Hrycko also anticipates more CCD camera guide applications cropping up, "as converters become used to them." The technology has, however, been available for more than seven years.

A more recent development from BST is a "watchdog function" in which an edge sensor can take over for the camera as soon as the web's guide line leaves the visual range.

Another alternative to analog is Fife's SE-34 LAZERWIDE, said to be the first laser-based sensor for web operations, and designed to replace moving sensor center guide assemblies.

Standard analog infrared sensors have a very narrow sensing range—typically less than 6" and most commonly about 1", notes Engledow. For applications with varying web widths where it is important to center guide the material to the center of the machine, this narrow sensing area requires the addition of an automatic sensor positioner to move the sensors as the web width varies, adding cost, complexity, and potential maintenance problems.

The LAZERWIDE, by contrast, can provide up to 73" of sensing area, and will automatically detect web width changes—providing better accuracy with no moving parts, Engledow contends.

Hrycko believes combining analog and digital sensing technology remains the best alternative for advanced packaging processing, including transparent substrate applications where certain sensor types are ineffective.

Sensing what's next

An emphasis on increased sensing area resonates through the ultrasonic guide arena. AccuWeb last year introduced the Ultrasonic Array compensated sensor with a longer 5" sensing area, allowing guide point adjustments without physically moving the edge detector. Research is underway to increase array sensing length to 12".

"Ultrasonics are traditionally thought of when guiding clear materials," says Henke, "but AccuWeb has noticed the acceptance of compensated ultrasonics into traditional optical sensor markets. A compensation feature can allow the edge detector to work in dusty, dirty environments where optical sensors would require constant cleaning and maintenance, or where air-type sensors can clog," he comments.

AccuWeb has also taken a leaner, meaner digital-controls approach with the Micro 4000 Net compensated ultrasonic edge detection system, which eliminates lengthy, labor-intensive cables used for wiring multiple guides by allowing system communications via a small shielded cable from the controller or PLC. The Micro 4000 Net microcontroller provides digital signal processing in a central control unit for up to four web guide locations and, packaging-wise, is commonly installed on bag machines at the unwind just prior to the v-board folder.

Amidst waves of digital emphasis, Coast Controls continues to take a different approach to guiding—one that operates entirely on low pressure plant air. Bob Duffy, marketing manager for Coast Controls, bases the appeal of Coast's All-Air guiding system, which features both air-controlled sensors and actuators, on its simplicity.

"Production and maintenance people appreciate the fact that the All-Air System simply connects to plant air and does not require any wiring or special shielded cables, switches, motor starters or other circuit overload protection," Duffy explains.

He also stresses the reliability and versatility of air-controlled sensors. "Coast's Air-Flow Sensors are suitable for any guiding application because they're impervious to buildups from paper dust, lint, various powders, carbon fibers, and other foreign matter, thanks to Coast's patented Servo Controller that allows a positive air stream to discharge from opposing orifices in the sensor. This same sensor is used regardless of whether you're running dark, opaque, transparent, or even reflective materials." Opting for air also eliminates issues with explosive environments or potential interference with corona treaters, electron beam ovens, or other equipment.

Coast will continue to emphasize simplicity and dependability in its systems, which are backed by a three-year-warranty, Duffy adds.