Several types of inspection equipment are available to converters, from the simple to the complex. On the basic side are handheld or press mounted strobe lights that help operators to visually inspect the printed product. A step above that are the camera based sampling systems that capture areas of the web. These video web inspection devices are the most prevalent in narrow web, according to John Thome, general manager for BST Pro Mark in Elmhurst, IL, USA. He says, "Those systems are used in 70 percent of narrow web presses out there."
AVT's 100 percent quality assurance PrintVision/Helios platform on a Nilpeter press
Val Rimas, VP of sales and marketing at Rotoflex International in Mississauga, ON, Canada, notes the difference between area scan and line scan inspection systems. "The area scan tends to be very good for text, but it's repeat specific," he says. "You're flashing an image based on the pixel read of the camera. The area scan is good because it's much more stable in picking up the image. What happens in line scan is you're reading line by line. It's like slicing the image into fine parts until you have the full image. It's not repeat sensitive, meaning you can have it as long as you want. You can inspect smaller details."
A final type of system is the 100 percent inspection system. Jim Doerr, president of TruColor Vision Systems Inc. in La Grange, GA, USA, says, "Camera based true 100 percent inspection systems automatically find and detail every printing defect. Once these repeatable and random defects are found by the 100 percent system, the operator is alerted via a display monitor or alarm."
Thome says that 100 percent inspection systems use line scan camera technology, which is different from other types of inspection systems that use CCD camera technology. He says the systems are "much more expensive compared to video — four to six times the price." These systems use a fixed lens so operators cannot zoom in and out to look at certain portions of the web. Therefore, according to Thome, 100 percent inspection systems are most frequently used on the rewinder instead of the printing press.
This brings up the topic of inline versus offline inspection. Inline inspection is conducted on press as the labels are being printed, while offline inspection takes place during the finishing stage on the rewinder.
Al Spendlow, VP of operations at AB Graphic International Inc. in Ontario, CA, USA, explains, "Inline inspection in most cases utilizes a camera and monitor, taking snapshots of the web, which allows the press operator to rectify print related issues as they appear without slowing or stopping. More sophisticated systems such as the FleyeVision Print machine log all print defects, which can be recalled in high resolution by the press operator at any time while running. This system prints a detailed defect report and stops costly overruns by determining the length of acceptable printed web produced."
With inline inspection on press, operators have the opportunity to correct problems. Since inline inspection systems allow for immediate action, they reduce the amount of waste associated with defective labels. Doerr adds, "Inline inspection can also contribute to faster machine speeds and an increase in productivity."
According to Lance Shumaker, president of Advanced Vision Technology (AVT) in Atlanta, GA, USA, "The big advantage to inline inspection is definitely cost savings, waste reduction and better productivity."
Offline inspection serves more of a quality control function since it helps find defective labels after they have been printed and allows converters to remove them before they are shipped to customers.
Shumaker says that deciding between inline and offline inspection depends on what the converters are trying to achieve for their customers. "In the pharmaceutical world, it's almost mandatory that they inspect on the rewinder," he cites as an example. Some converters use both inline and offline inspection methods, though that is not too common. Shumaker says more converters are starting to use inline inspection.
Because printing accuracy is an essential part of the converting process, companies are always working to improve their inspection equipment. Ernest Schneider, business development manager at Erhardt & Leimer in Duncan, SC, USA, cites three areas that are helping to improve inspection. "New digital cameras are replacing older analog camera technology in the web viewer product range. The higher picture resolution is resulting in better image quality and color fidelity. New three-chip color line scan camera on 100 percent inspection systems will now better find color shifts and minor print errors. Adding inspection into the production process as early as possible minimizes the potential to produce and/or ship bad product while maximizing potential profit."
Thome agrees that digital technology offers better inspection ability than analog. He also says BST Pro Mark has begun linking visual systems with 100 percent inspection systems. "We make a complete workflow system out of this. On press, we can put a system that can identify defects. Downstream on the rewinder, we put a reading device that reads marks on the edge of the web," he explains.
The Omega SR1300 fitted with AB Graphic's FleyeVision Image Control System.
Another development gaining converters' attention is PDF inspection. Shumaker explains, "You have the ability to take a PDF file of customer artwork and compare the actual PDF to the product that's being inspected on the roll." This can be helpful not only with graphics, but also with text. Shumaker cites different languages and small text size as two examples of applications in which PDF inspection would be useful.
Spendlow says, "Recent years have seen great strides in PC based electronic print face inspection. These systems now are seen at almost every level of label type from pharmaceutical and prime label to simple one color bar codes, and they eradicate a multitude of defects as well as the need for alternative equipment such as flag detection, splice detection, missing label detection, strobes, and bar code scanners."
Lederle Machine Co., Pacific, MO, USA, manufactures tabletop rewinding and inspection equipment. Paul Young, national sales manager, says, "Lederle now offers rewind tables with PLC (programmable logic controllers) and VFD drives. In addition, Lederle also uses operator interface control panels that can read out any text or language you could want. Most of our machines now sent to Latin America and Mexico all read in Spanish. The electronics today offer many more possibilities to adding bar code readers, camera systems and missing label detection, to name a few."
According to Doerr, "New developments are being made in true 100 percent inspection technology in terms of being able to inspect wider web widths and/or on faster production runs (press speed). Until recently, 100 percent inspection systems had some limitations in terms of maximum web widths and higher press speeds." He continues, "As with most technology, camera based web inspection systems are becoming increasingly feature rich while simultaneously leveling out in terms of price/cost." He compares the increase in features without a rise in cost to that of home and office PCs.
A wide price range exists with inspection equipment because of the differing systems. Schneider offers a price breakdown: "Strobe light inspection can range from a few hundred to a few thousand dollars depending on the size and quality of the strobe. Bar code readers and densitometers range from $500 to $15,000. The price range for viewing systems is $6,000 to $60,000. The price range is affected by system configuration and tasks to be performed. The price range for 100 percent inspection systems is $50,000 to $80,000. The price range is affected by camera type (grayscale or color) and width to be inspected. Fully integrated inspection systems can range from $100,000 up depending on the number of presses to be supported."
Jack Woolley, general manager at PC Industries in Gurnee, IL, USA, says, "Basic web viewers start at $5,000 or $6,000. As you get into defect detection systems, those range from $15,000 up to $100,000-plus." He says the defect detection systems are more expensive because they detect smaller defects while allowing higher web speeds.
BST Pro Mark's Premius camera on a Gallus RCS 330 press
Spendlow says, "Costs are far ranging and usually do not include the platform or rewinder the inspection equipment is ultimately mounted to. Strobes vary greatly but could be considered a minimum requirement, starting below $1,000. AB Graphic International provides a wide series of vision inspection equipment on or off press that can be integrated to almost any rewinder or printing press. This type of system starts at $40,950. Larger bespoke fully integrated vision systems for pharma applications with rewinders can cost upwards of $200,000."
Although these systems appear to be expensive, Doerr believes the price is justified: "We always remind our customers that the cost of not having an inspection system — in terms of waste, lost productivity, inferior quality, longer make-ready — is much higher than the average investment required to incorporate this technology."
Most common systems
When it comes to inline inspection, Thome says, video systems are the standard. "They're everywhere. They're on 70 percent of narrow web presses. 100 percent systems are well below 5 percent. They are much more common on rewinders," according to Thome.
Woolley believes the basic web viewer is the most commonly used form of inspection. "The operator zooms in and out with this manual type system. It's located on the printing press." He adds, however, "The other types are becoming more common."
According to Shumaker, 100 percent inspection systems are used most often in narrow web. He explains, "There are people that are just using viewers, which typically use a strobe flashing camera. An operator has to sit there and watch the monitor for defects. It's very unproductive and the operator can make mistakes. Automatic inspection automatically alerts the operator when there's a problem, and the operator can immediately inspect the defect and make a quality decision."
Doerr sees a mixture of systems in use. "Historically the narrow web market embraced a full range of inspection system capabilities. This included very basic entry level systems, midrange semi automated systems, as well as the higher end active inspection systems. Recently, TruColor has seen investment trends move towards either the high end or low end of the inspection spectrum in terms of capabilities. Narrow web printers seem to fall into two categories now — either the entry level basic sampling systems or on the very high end 100 percent inspection systems."
Spendlow thinks cost has an effect on converters' inspection choices. "The most common types of inspection equipment in my experience are the less expensive, when less expensive will suffice. In the majority of cases, inspection is carried out on an inspection rewinder and consists of an experienced operator visually inspecting the print with the aid of a strobe searching for missing labels, flags and print defects."
When to use inspection equipment
Certain industries come to mind when talking about inspection. A major one is pharmaceuticals because the text needs to be accurate for patient safety information.
An example of inspection equipment designed for pharmaceutical labeling is the Advanced Machine Vision System from Rotoflex. The system uses a reference based inspection method for quality control. During what the company calls a "Learn" process, the system stores a known good image and then compares it with each consecutive image using tolerance for color deviation, registration and defect size. Rotoflex offers two machine types: Single Pass Inspection (SPI) and Dual Pass Inspection (DPI). Both are meant for security sensitive industries, including pharmaceuticals.
According to Woolley, "Another application is security printing. That's where each item is serialized and it's used for anti-counterfeiting and product identification. It's important to verify the variable numbers on each item so all the numbers are correct."
Spendlow says, "The most important applications from a label manufacturers' standpoint are when their customers demand high levels of quality and accuracy, be it label quality or automated data readability."
Thome agrees that pharmaceuticals aren't the only products where inspection is frequently used. He cites high-end cosmetics, food labels and wine labels as other areas where inspection is frequently used.
Doerr sees value in using inspection equipment across the board. "We believe every printer/converter, in almost every application, requires print inspection. The cost of man hours, machine time, materials (substrate, ink, etc.) can be reduced by implementing an inspection system. Basically with an inspection system, problems and defects can be detected earlier and corrected during the printing process. This allows quality to be manufactured into the products as opposed to only being removed after the fact."
The main goal with inspection equipment is to make the process simple. Woolley says, "The biggest challenge is to make the systems as easy to use as possible. A typical rewind operator might not be computer literate. We tend to use touch screen monitors. They're easier to operate the equipment. Our approach is to continue to make it easy to use."
Shumaker says, "The only challenge is making sure the operators are comfortable with use of the system. Once the operator finds a defect he would've missed, the light bulb goes on." He says AVT offers full training for its inspection products.
The Rotoflex VSI eDrive Inspection Rewinder
Spendlow believes human error can cause the most problems. "Today's technology means that challenges are more easily overcome, especially when the human element is factored out of the equation by means of a PC based camera system. In such cases, the challenge would be not making a bad call and overriding a detected defect. Of course not all label converters have such technology. In such cases the challenge when inspecting 'manually' would be operators staying focused during operation."
Doerr discusses a different issue that actually could improve quality. "If I were forced to point out a drawback or challenge, it would probably revolve around a 're-establishment' of customer-acceptable product. When an inspection system is incorporated, operators can now see, under magnification if desired, more details and better images of the product as it is being manufactured. Consequently, this can lead to the re-establishment, or recalibration, of the quality standards. What once was acceptable may no longer be. Establishing new quality standards initially may be challenging for some, yet the end product is of a much higher quality."