From Image to Panorama
Variation in web inspection systems lets converters see just what they want to see.
By Susan Friedman
Whether package printers' fiercest print nemesis is skip-out, smudges, streaks, register or color, the web inspection market is teeming with improved approaches to sending defects packing, whether the budget is basic or no-holds-barred.
In the narrow-web market, Brian Tithecott, marketing manager for Focus Automation Systems, reports strong sales to pharmaceutical, health and beauty, and prime label printers with a need for high quality, and in the case of pharmaceutical printers, perfection in each impression.
"Wide-web printers," he notes in comparison, "are looking at inspection to improve yields. The system on-press must quickly identify problems, solve those problems in real time, and mark the suspect material so printers can get on with producing good product."
For return on investment, he sees the wide-web segment looking for lower resolution, higher speed, lower initial cost and easy set-up and use.
Jim Doerr, vice president sales and marketing for TruColor Video Systems, emphasizes despite wide or narrow needs, a system choice will typically still revert back to basic budget constraints. Printers with the funds to purchase multi-million-dollar presses are often more open to higher-end inspection systems, he explains.
Keeping an eye on advances
Bill Blethen, president of Unilux, reports that stroboscopic inspection lighting, which can eliminate visual blur at speeds to 5,000 fpm, continues to evolve. Unilux recently added a series of sensors to trigger its lighting synchronously to repeats.
Converters most commonly using strobe lighting are those running labels at high-speeds with short repeats, Blethen relates. Strobe lighting can also take over after camera-based inspection of print defects to check for diecutting inconsistencies, or variations in the thickness or density of the substrate.
On the video system side, converters will find a nearly blinding array of upgrades. "What was popular two years ago in lower grade inspection systems at low prices is being replaced with the latest technology," says Karen Huber, director, global sales at PC Industries. A sampling
TruColor Video Systems' 1000 Series system for narrow-web applications now features a smaller camera housing (4" x 9" x 12") for inspection in tighter spots on-press. A higher-end "Program Scan" feature has been added to its mid-range 2000 Series, allowing users to program up to 36 camera positions. The 2000 Series' camera has been upgraded to a 570 image line, three chip device, providing resolution that pays off in expanded fields of view. Additionally, TruColor's 4000 Series system has moved to a networkable Windows NT operating system.
BST Pro Mark's Series 2000 systems include a new, proprietary camera design that is said to produce the highest resolution, one-chip image available. BST has also advanced its Defect Prevention Eagle system, which combines automatic web analysis with a powerful operator interface.
Focus Automation Systems has concentrated its efforts on 100 percent inspection of the complete web and ease-of-use. In addition, advanced inspection algorithms now adjust for long period defects such as ink fade or registration wander, as well as quickly occurring ink splatters or missing characters to significantly improve the percentage of positive defect identification.
PC Industries' GX100 and GX200 family of higher grade systems offer resolution almost equal to a three-chip camera system, using "full-scan" cameras with 480 TV lines resolution, and are equal in price to mid-grade systems. Its new VIPER system blends a flexible Windows NT touch-screen with print defect detection, template matching, image tracking, optical character resolution and statistical process control features.
Video inspection's sharper images are taking on trickier objectives. Fife recently unveiled an optional front-to-back registration feature for its Inspectra system, providing a simultaneous overlay of the front and back of the web to check alignment of front-to-back printing or front printing to back-side coating, such as cold-seal adhesive. The feature also includes a clear coating package to enhance views of hard-to-see varnishes and clear coats.
Advanced Vision Technology (AVT), which asserts the ability to sometimes see slight streaks, register and color defects invisible to the human eye with its PrintVision Genesis and 9000NT systems, just released its RiteSeal cold-seal inspection system for clear and tinted adhesives. Advanced algorithms and a unique computer architecture also allow the systems to handle stretching, shifting and vibrating of transparent and flexible substrates.
High-end viewpoints
All types of inspection systems claim to perform 100 percent inspection. Package printers must be familiar with camera capabilities to evaluate what a system truly provides: Array cameras inspect 100 percent of a captured frame; line cameras inspect 100 percent of the web.
If inspection of 100 percent of the web, 100 percent of the time is the goal, line cameras can deliver, detecting the random defects of critical interest to pharmaceutical label printers. But who else is buying?
"Since the quality and performance of most presses today has improved, the need to identify random defects has diminished for most applications," says Steve Hrycko, director of video web products, BST Pro Mark. "Most applications do not require the need to see 100 percent of the web, but do require the ability to perform high-speed analysis on a percentage of the web to control the printing process and eliminate trend defects."
"We must differentiate between 100 percent inspection and 100 percent detection," comments Orit Eyal, AVT product marketing manager. "One hundred percent inspection systems provide a good solution for webs up to 12" wide. On wider-web applications, we may recommend process control solutions with higher detection capabilities for evolving or repetitious print problems."
Closed-loop—the other wait-and-see aspect of inspection—does have progress to report. "True closed-loop control—feeding back information to the press for automatic response—is still a challenge," says Tithecott. "Where we see value in control technology that can be applied today is Automated Intelligent Converting—100 percent web inspection, knowing where every defect is and communicating this information to downstream converting and finishing equipment to automatically remove suspect product."
Another approach to closed-loop comes from vrp Web Technology, which configures high resolution inspection and web behavior controls into one operator interface with its InVision system, effectively tying inspection to motion, tension and speed control.
