The human eye is an astonishing mechanism. With its partner, the brain, it can distinguish shapes, hues, patterns, depth of field, motion, shade, color density, all kinds of intricacies of the universe. For years, the human eye and brain sufficed to serve as the quality assurance device in the labeling and packaging world. Experienced printers could look for a fraction of a second at a label and know whether it would pass muster with the customer. Then things got complicated.
Narrow web converters still use human beings to inspect labels. The practice is probably the most common method. But customers are becoming more graphics-conscious, more conscious of the legalities represented by the text of their labels, more demanding when it comes to perfection. In the past few years we have begun to hear the term “100 percent defect detection.” The human eye-brain team now has competition from some highly sophisticated equipment — the camera and the computer. With enough fine-tuning, these man-made inspection objects can come to a full stop upon encountering a fly speck. Literally.
Label inspection takes place at several steps along the converting process. In the best plants it takes place at every step. Methods vary. Press operators might employ simple means, such as strobe lights, which stop the action on the web for eyeball comparisons. Others will install cameras poised closely above the moving web, cameras that will vary in degrees of sophistication. They can reveal on the connected monitor a simple image of the web, or they can display on a split screen the master image for comparison with the moving image. Some have alarms that sound when a defect is encountered.
Often the more serious and dedicated inspection takes place in post-press, after the printing. Inspection equipment at this level ranges from the simple rewind table to the complexity of the 100 percent machines.
Several companies have been manufacturing post-press inspection equipment for years, companies whose names have become household words in the industry. Many of these machines perform the slitting and rewinding tasks, leaving the inspection to the humans. Others have cameras of varying capability incorporated into them, with accompanying software and hardware that relieves the operator of the exertion of staring at a web moving at 700 feet each minute of the shift.
Viewing the web
Allowing a camera to watch the moving web is a practical way to inspect for flaws during the print process. Web viewers can run from a few thousand dollars on up to the five figures.
|PC Industries’ RX100 system|
Among companies that manufacture a variety of systems is PC Industries, of Gurney, IL. According to John Woolley, vice president of sales and marketing, the company’s RX100 low cost system incorporates a digital camera for web inspection. The $6,000 system, he says, is designed for label presses. The camera can be rotated for more analysis of the web. “Web viewers have been around for a long time,” says Woolley. “Now, with a digital camera, a lot more can be viewed on the web. A digital image contains a lot more information in it.”
TruColor Vision Systems, based in LaGrange, GA, offers a basic system it calls the 1000 series, typically targeted to the narrow web industry. This no-frills model requires manual adjustments to view other parts of the web width. “If the operator is printing three labels across the width of the web, or four around, the camera will automatically step around the cylinder” says Jim Doerr, president. “But if the operator wants to see the web across, he has to reposition the camera manually.”
Doerr estimates that probably 80 percent of the 1000 series is manually controlled by the operator. An upgrade to motorized positioning is available.
TruColor’s 2000 series, described as “midrange,” offers extra features. “It adds a bit more automation to the system,” Doerr says. “The camera can be programmed to go to certain places in the repeat.
Standard image areas in most cameras are about 4"x3". Many of them offer a zoom capability to allow a view of the process dots. TruColor, which does not offer a fully digital camera yet, uses an array camera that offers 480 image lines of resolution. “When we started manufacturing web inspection systems in 1992, the camera of choice was a Sony or a JVC,” Doerr notes. “The Sony offered 330 lines of resolution. Cameras have improved since then, and for a single CCD camera 480 is considered high resolution.” In the company’s higher range systems they use a three-CCD camera, which offers almost double the resolution.
“It’s infrequent to come across any plant in the label industry today with no inspection systems in the facility at all,” says John Thome, VP marketing for BST Pro Mark, Elmhurst, IL. “The visual systems have become pretty much standard equipment on narrow web presses.”
The entry-level BST system parks at one position on the web, usually over a register mark, and watches the mark throughout the run. The company offers other systems that can monitor the color, monitor bar codes for defects, and more sophisticated functions.
Thome says that no new developments have been made in CCD camera technology in the past seven years, because the major manufacturers saw that it would die and be replaced. “All new developments in camera technology have been in the digital arena,” he says. “It’s a matter of time before most systems go that way. There are so many advantages of digital over analog, some that are transparent to the customer, some that are visible, such as picture quality and color fidelity.”
The monitor is a critical part of the web vision inspection system. It can, in fact, make the difference between a good system and a bad one. “We’ve always felt that the monitor is an extremely essential part of the system — not the place to scrimp,” says Thome. “It’s like buying a good stereo; you don’t want to put cheap speakers on it.”
BST used Sony monitors for years, but recently switched to NEC. “Sony monitors always stood out in the aggressive tests we conducted, but we ran the tests recently and that’s not the case today. Most of Sony’s competitors have caught up. We couldn’t see any differences, but Sony charges a premium price.”
BST’s Genius Digital camera system has replaced its Eagle system, says Thome. “It offers virtual repeat, which means that if you want to see a 20" repeat on a 20" web, you can. The operator just touches a part of the image on the screen and the camera will center there. The camera is creating the digital repeat by stitching all of the images together. We have trademarked the term for it — Virtual Repeat Technology,” he adds.
PC Industries tackles the high end of the web viewing market with its Viper inspection machine, targeted toward the pharmaceutical industry. “This unit can be mounted on the press or on a rewinder,” says Woolley. “It works at high speeds, and can pick up filled-in characters on four-point type at rewind speeds.
“More customers are looking for intelligent inspection systems,” he adds. “When people think of defect detection systems, they think six figures, but the costs have come down a lot. What you get for your money, along with faster processes, blows away what you could get three to five years ago.”
Today’s camera systems allow the operator to load a “golden image” into the companion computer, an image that serves as the master design. The inspection equipment “learns” the image and is able to spot defects in the passing web at high speeds. “We can pick up the difference between a comma and a period in four point type,” says Woolley. “The system can measure color values and alert the operator if it’s out of tolerance.”
TruColor produces a TG4000 system, described by Jim Doerr as a Windows NT environment with a touch screen. “It checks UPC bar codes, monitors and checks color to Delta E, performs active inspection with the software and hardware making the decisions as to what to do. Converters printing higher end products, such as wine labels, have more interest in the 4000 system equipment.”
|TruColor Vision Systems’ 1000 Model||TruColor Vision Systems’ 2000 Model|
Offline inspection rewinders
Among the basic workhorses in the inspection arena are the tables, such as those built and marketed by Web Techniques of Fenton, MO. With these units, printed and slit rolls are rewound horizontally on steel tables at speeds that can range from 500 fpm at the start to 2,000 fpm at the end of the roll.
“Our inspection tables range from those in which the operators view the material as it moves in front of them, to those that use a strobe light, which lets them look at more material at a higher rate of speed,” says Ken Barstow, president of Web Techniques.
“Currently we offer a bar code validation system, in which the reader examines each label as it comes by to determine if the bar code matches the master code,” he says.” The system reads each label and stays in motion only if the label is OK, Barstow adds. In other words, it doesn’t shut down for correction if it reads a bad label, but only if it fails to read a good label.
The company is at work today on an inkjet printing option for the machine, which will allow printing of lot codes and date codes on labels. Eventually, Barstow adds, “we want to be able to print consecutive bar codes, then verify that the codes are consecutive with no duplication.”
Label converters with demanding customers require inspection equipment that will enhance their production lines, maintain the high speeds they require, and live up to the exacting standards they have set for themselves and which their customers have come to expect. One such company is Diversco Inc., a division of the NOSCO Printing Group in Carrollton, TX. Diversco produces pharmaceutical labels for ethical and over-the-counter products.
Not long ago, the company decided it had to step up in its inspection capabilities. “The first thing we did was to determine what defects we had to be able to detect,” says Craig Wilson, technical manager. “In pharmaceutical labeling the copy is of primary importance, even above and beyond graphic quality in some cases. We had to identify a machine with the resolution that allowed for the detection of defects and errors in small-point type.
|The Omega Flytec 2000 at Diversco Inc., Carrollton, TX|
“We researched several systems, and performed trials on a few, but ultimately decided to purchase the Flytec 2000.” The system is sold by Omega Systems, Danbury, CT, part of The Burton Group, and features the Geiger Inspection System.
“The unit features a waste take-up shaft next to the unwind, allowing for the removal of defective product onto an independent spool for disposal. Also included are flag detectors, which allow the machine to reverse a short distance for the removal of defective product as identified by the operator. All of these features surround an inspection and a splice table that aides in the removal of unwanted product.
“When the vision system encounters an error, the machine stops and reverses using an accumulator,” says Wilson. “This action places the defect directly in front of the operator for disposition. In addition, the error is highlighted on the monitor and correlates to the web in front of the operator. When an error is detected the operator can learn the defect out, skip the label and begin the inspection again, or remove the non-compliant label via the shaft located above the unwind.”
“The system is very very sensitive: the camera resolution is very high.” Wilson says, “certain types of materials contain particles that can set off the defect detection if the system is tuned to a fine degree. The major advantage to this type of system is that it catches everything, and major disadvantage is that it catches everything.”
|The Rotoflex Model HTI|
Rotoflex International, of Mississauga, ON, builds high-end inspection slitter rewinders that offer “100 percent real time automated inspection. That’s what’s available today,” says VP Val Rimas. “Traditionally in our business, you would have some electronic devices that would inspect a bar code, or a missing label device, or others that would isolate a specific task.
“Today we offer every aspect,” Rimas says. “They come with different price tags, depending on how wide you want to run. In our industry we are seeing a shift to wider webs. Customers today want faster turnaround times, so the converter can’t have product stacked up behind the finishing equipment. There has to be greater throughput.
Rotoflex offers a VIR model in widths up to 26". The MIR is a smaller version. “These are pure inspection machines,” Rimas says. “They run up to 400 meters a minute — that’s about 1,200 feet. They clean up all the bad material and go to automated slitting.”
The company also produces an HTI and an SPI model, “which are strictly dedicated to pharmaceutical label inspection. These are camera based systems with different types of vision. They have line scan cameras or area scan cameras.”
“Inspection is a huge area right now,” Rimas adds. “There are so many issues with regard to inspecting color. People want to match Coca-Cola red or Fuji green. They want to have the ability on inspection machines to detect anything that falls out of specification.”
|The Arpeco 20-20 inspection system|
The recently-introduced Arpeco 20-20 inspection rewinder includes a Shuttle Retrieval System that enables defect correction without affecting the slitting process.
“Any machine that reverses while you are retrieving a fault cannot actually be a slitter rewinder as well,” says Allan Prittie, president of Arpeco, Mississauga, ON. “To back up you cannot then go forward through the slitting system again. It is impractical to inspect, slit and rewind multi-web applications along with retrieving a fault by reversing the web.
“That means two passes — one for inspecting, one for rewinding. If you slit and rewind, then go through inspection, you multiply the number of faults by the number of slit widths. There are accuracy problems with that,” Prittie notes. “And there can be serious tension problems.
“The Shuttle Retrieval System on the 20-20 precludes that. When the machine or the operator finds a fault the machine will stop. The retrieval system will reverse the fault back to the inspection area, but the unwind and the rewind don’t move. The system contains an accumulator and a de-accumulator, so that what you retrieve from the rewind you add to the unwind area. You maintain the length.
“This is something that customers have wanted for many years,” he says. “With the 20-20 you have one pass instead of two, obviously fewer operators, less floor space, fewer passes with the rolls, and less damage.”
The system is popular not only with pharmaceutical label shops, but also with those who make labels for cosmetics and security products.
There is an additional benefit to improving the capabilities of the label inspection operation besides producing perfect labels to please the customer. Sophisticated equipment can improve the performance of the work force in more ways than one.
“There is no more tedious job in the printing business than inspection,” says Diversco’s Craig Wilson. “The overall well-being of your inspectors is much higher with a piece of equipment like the Flytec. It allows the operators to take care of some other functions of the process, because they don’t have to do the visual inspection.”