by Cassandra Balentine
For printing and finishing, inspection/verification systems improve output quality and document security during the print production process. These solutions help reduce labor costs, improve integrity, implement audit/tracking, and ensure data security. Popular applications include print quality inspection, color quality monitoring, MICR and barcode verification, matching, assembly integrity, and forms verification.
“Vision/inspection systems are integral for any vertical, particularly in this era of high-speed production and short-run applications,” says Don Dubuque, director of marketing, Standard Finishing Systems. He explains that at the printer, inspection systems perform a number of quality checks including color tolerance, pattern matching, white space verification, ink or toner spills, voids, and jet-outs. At the finishing end, inspection systems perform sheet and set-level integrity checking for booklets and verify the order of signatures during folding.
Inspection/verification systems manage quality control and maintain efficiency on shorter runs while meeting faster turnaround time demands.
Role in Digital Print
Inspection and verification systems hold an important role within digital print.
Digital printers are used more widely to produce large volumes of labels, packaging, and publishing materials. According to Nick Khatri, group marketing manager, Lake Image Systems Ltd., unlike traditional offset printing, digital printers are allowed a high degree of flexibility and variability between jobs and within the job itself. “For example, serialized or variable data labels can have a unique number, text, barcode, or quick response (QR) code on every label printed in multiple lanes across the web to maximize production. Each code or barcode needs to be verified to prevent issues when the label is applied to a product, shipment, or document. Also, these camera systems can check for print quality issues such as correct print registration, color variation, toner marks, streaks, and voids,” he offers. Camera inspection is increasingly important to replace outdated web viewing systems or manual inspection quality assurance (QA) processes.
Khatri says inkjet digital printing has increased flexibility even further. “Inkjet printheads on existing traditional presses, converters, and production lines allow companies to build hybrid systems for maximum efficiency and profitability. Camera inspection systems are a growing requirement to catch inkjet printing errors such as misaligned inkjet printheads, missing or mis-positioned print, or even operator error in setting up dates, lot numbers, or sequential numbers.”
Lucia Dauer, product manager, print inspection, ISRA VISION, points out that digital printing requires new processes, workflows, and high automation. Brand owners have a high demand for customized and short-run goods or individualized corrugated boxes or folded cartons, which means a packaging printer must be able to react to digital print quality issues to keep the quick turnaround and achieve quality control. Inspection systems tremendously reduce the lifespan of a digitally printed defect.
Ralf Wirtz, sales manager, GMBH sites, AB Graphics International, says camera solutions are added to digital or hybrid presses and finishing lines. “The camera can detect the defects at much higher speeds in comparison to the printing speeds of the digital press, meaning that one finishing line can furnish multiple digital presses,” he explains.
Similarly, solutions like the Standard Finishing Hunkeler WI8 Web Inspection System are able to capture high-resolution images at production speed using a Compact Image Sensor (CIS) scan bar. These full-page images can then be compared to a control sample image to quickly catch colors shifts, spots, streaks, positions, and contours to help ensure that quality and content errors are caught early.
Vision/inspection systems check text images for print errors, recognize and classify all standard barcodes, check data in OCR characters, and check braille for errors. Specific to AB Graphics’ fleyeVision system, Wirtz says images are recorded by a digital line scan camera with between 1,024 and 8,196 pixels as a color or a grayscale picture.
Image processing is handled in the computer where output like labels are continuously recorded and compared to a previously created master image. There is also the option to verify the master image using a PDF comparison process. “When equipped with two cameras, a fleyeVision print machine can be used to inspect labels simultaneously both front and back or using different light sources at a single path,” shares Wirtz.
When an error is detected, its type and position are indicated on the monitor, allowing the operator to then remedy it. Wirtz adds that any stored errors are then processed in sequence. With bi-directional machines the corrected error is again subject to inspection after fleyeVision has been restarted, guaranteeing 100 percent inspection.
Features in Demand
Because vision/inspection systems are essential for printing, Dubuque says that anyone producing commercial publications, direct mail, food packaging, newspapers, pharmaceuticals, transactional mail, tickets, or any other application requiring variable data and precise information benefits from the technology.
Paul Stinson, sales director, Lake Image Systems, points out that certain applications require higher levels of inspection sophistication than others. “In the security printing industry for example, where every document, label, or stamp has a monetary or security value such as ID cards, vouchers, authentication labels, tax stamps, or lottery/gaming applications, every item has to be checked for printing defects before it can be used.”
He explains that here, even a small printing flaw must be caught to meet very high levels of quality standards. The camera inspection system checks for glitches, ensures variable data is printed correctly and in the right place, and confirms there are no missing or duplicate items within the entire print run.
“Sometimes, the check must go across multiple print runs. In most cases the data requiring verification is on highly reflected/holographic surfaces or printed in UV/IR fluorescent ink, which require special lighting, filters, and optics to do the job correctly.”
“In this era of short turnaround times, manual inspections are no longer feasible. Inspection systems can be placed on printing presses, sheet feeders, saddlestitchers, perfect binders, paper folders, and mail inserters to identify errors in production in real-time. Inspection systems can perform verification of material imprinted with virtually any standard symbology, including one and two dimensional code, OCR characters, MICR, addresses, or even OMR markings at the click of a mouse or via touchscreen. Any print provider knows that mistakes are costly, so inspection systems are integral in guaranteeing product quality without increasing labor costs,” explains Dubuque.
The demand is for 100 percent defect detection. Dauer says this means using the features of defect classification to detect and warn on all typical digital printing defects, including streaks, banding, missing prints, spots and splashing, missed registration, and color variations.
One important feature of vision/inspection systems is the ability to detect relevant defects. For example, the CartonSTAR vision system will inspect only relevant defects, i.e., on corrugated material to avoid false alarms that may lead to unintended waste. “When we talk about material, our substrate compensation feature is in demand by digital printers in corrugated packaging,” says Dauer. As corrugated boards show structures in their material and the typical waves may be visible.
Color measurement features are also attractive. “Measuring color—both relative or absolute—is important for digital printers to see the color stability within a job run or trace absolute color values to see if it matches the brand owners’ requirements,” shares Dauer. She explains that threshold charts allow operators to see if the print run is within a given delta E deviation with one look.
With any technology, there is generally room for improvement or specific considerations that should be addressed. There is a continued push for heightened productivity and more automation.
“Inspection systems are not one-size-fits-all,” admits Dubuque. He says they must be properly programmed to meet the specifications and needs of each print provider, which can require a lot of setup and a complex integration process. “This is especially true of shops that are new to automated inspection systems. Each new generation of inspection systems are improving on the steep learning curve, but this is an area that still needs to progress in order to bring more on board.”
Martin Keats, managing director, Lake Image Systems, says it still encounters sites where camera inspection systems are an afterthought, when it should be considered an integral part of the planning process. “Some view camera inspection as a ‘nice to have’ until they are required to meet a contractual or regulatory requirement, or find that their in-house manual QA or sampling process is just not good enough and that it is reducing their operational throughput and increasing print waste.”
Dauer says every operation that goes into digital printing faces the demands for a digital workflow. She points out that ISRA VISION is also a part of the digital workflow. “For the future, we see room for improvement in standardized interfaces that will allow even higher automation of the digital print workflow. Also, the movements in Industry 4.0, standardizing interfaces, and workflow of data also support in the packaging industry—especially the digital printing workflow.”
She adds that today, in order to manage the customer print jobs in a digital workflow, its vision system can be integrated to receive production management data of an MIS.
As digital print systems and supporting technologies advance, vision/inspection systems continue to evolve.
“Over the past few years, inspection systems have evolved to keep up with higher speed presses so that quality control doesn’t come at the cost of production speed,” states Dubuque.
“As digital printing technology has advanced, camera inspections systems have also evolved alongside,” agrees Khatri. As digital printers increase their print speeds and image quality, advances in camera, optics, LED lighting technology, and PC processor and networking speeds have also enabled inspections systems to keep up. “For example, at Lake Image Systems we have optimized our Discovery Multiscan3 software to use the latest in 16K line scan camera technology, run on the latest PC hardware, and on Microsoft Windows 64bit operating system. This has allowed us to increase the image resolution we can capture to detect smaller and smaller defects, increase our image capture rates, and perform our inspection processing at higher speeds, whilst maintaining our hardware costs.”
When used effectively, today’s vision/inspection systems can reduce waste by identifying defects in real-time, even on high-speed presses, to prevent costly re-work and generate a variety of production reports for compliance. This is especially important when presses are installed roll to roll because there is no longer an opportunity for a visual check. “Print providers need to catch errors before the web is rewound.
Inspection systems can now automatically stop the line if there are extreme issues in production. This level of detection on inline systems helps reduce waste and overprints for the end user—catering to the digital printing model of short runs and print on demand technology. For offline or near line systems, vision/inspection systems can verify that everything is printing in the correct order without duplicates and mark individual pages for removal further down the production stream,” comments Dubuque.
Wirtz says its inspection technology is constantly evolving. “The fleyeVision 4k color system is the latest model, which shows a 50 to 80 percent higher level of performance—maximum inspection speed. This enhanced performance is driven by an OCR and barcode inspection rate four times faster than before and is linked to hardware with higher performance and software optimization.
In addition, Wirtz believes that quick makeready times and integration with MIS and ERP helps aid digital printing and the production of many short-run jobs is an evolving area.
Dauer adds that the ISRA surface vision system and inspection technology are ready for use in networked production processes. “Concentrating on detecting the typical defects of digital print through intelligent algorithms. As digital workflows produce a lot of data, it becomes valuable once it is turned into relevant information. With our EPROMI software we aggregate information and analyze and visualize data to provide reporting and analysis tools, like statistics, trends, and charts—so a digital printer can determine the future strategy of flawless production.”
Seeing it Through
Vision/inspection systems are essential for print providers in any vertical, particularly in this era of high-speed production and short-run applications. Continued integration advancements help these systems evolve to support digital workflows and Industry 4.0.
Oct2021, Industrial Print Magazine