High-Tech Vision Tools Look for Trouble
New inspection equipment checks inside and out to find packaging problems.
William Leventon, Contributor
Cutting-edge package inspection systems don't stay that way for long. Thanks to ever-faster processors, the latest machines always offer better performance than their predecessors. New software and hardware technologies keep expanding their capabilities, improving the inspection of both packages and their contents.
But accuracy isn't enough. Packagers also want inspection equipment that's fast. "Nobody's going to be willing to slow down a production line to acquire information," says Robert Fortier, vice president of AC Compacting LLC (New Brunswick, NJ), which sells inspection equipment. So equipment manufacturers are also working at reducing inspection times. Meanwhile, inspection machines continue to shrink, making them easier to incorporate into packaging lines.
|The Date Code Inspector from Optel Vision inspects date and lot codes on labels, boxes, tubes, or bottles.|
But improving equipment doesn'tmean increasing prices. Inspection systems are getting cheaper as they get better, notes Phil Heil, chief technology officer at DVT Corp. (Norcross, GA), a maker of machine vision systems.
With inspection systems operating better, faster, and cheaper than ever before, packaging professionals are using them to spot trouble all over.
LOOKING AT LABELS
One popular role for vision systems to play on packaging lines is label inspection. One recent innovation comes from Label Vision Systems Inc. (Peachtree City, GA): the LVS 3200, a camera-based system that checks packages for bar code presence, sequence, and quality. For auditing purposes, the system also records what it sees and stamps all transactions with dates and times.
The LVS 3200 can handle 60 transactions a second, making it faster than laser inspection systems, explains Tim Lydell, director of sales and marketing for Label Vision Systems. With no moving parts, Lydell adds, the 3200 is also less likely to break down than laser systems, which are currently cheaper and more common than machine vision for label inspection.
Besides checking label quality, machine vision systems can read labels on packages. For example, Cognex Corp. (Natick, MA) has developed an algorithm that allows its vision systems to read reduced-size symbology (RSS), a relatively new symbology put forth by the Uniform Code Council Inc. Used for tracking or identification, RSS is put on packages too small for a regular bar code label, explains George Blackwell, director of product marketing for Cognex.
Often, vision-based systems can be foiled by clear labels. In labeling operations, sensors must identify the leading edge of a label to determine whether the label is ready to be applied or has been applied properly to a product. But when both the label and the carrier material are clear, an optical sensor can't tell the difference between the two—and, therefore, it can't detect the label edge.
For these situations, Lion Precision (St. Paul, MN) offers sensors that use patented capacitance technology to measure thickness. Since a label is thicker than the carrier material, capacitive sensors can distinguish between the two, notes Nick Marchuk, the firm's sales manager.
Capacitive sensors also work about 10 times faster than their optical counterparts, Marchuk adds. With a 20-microsecond response time, he says, the sensors can keep up with the ever-increasing speeds of labelers, a fact that brings in new customers whether they use clear labels or not.
To meet throughput demands, InSight Control Systems International Inc. (Safety Harbor, FL) has introduced a new family of high-speed machine vision systems that check caps, closures, and containers for defects and cosmetic nonconformities. InSight2000 vision systems can perform full-color high-resolution inspections of more than 3000 parts a minute, says Rich Hebel, the company's vice president of sales and operations.
InSight2000 systems inspect containers using patented MicroOptics technology. Prior to an inspection, MicroOptics essentially turns different, oblique planes of a surface into a single plane. This means that no features are hidden from the system because of surface orientation, Hebel explains.
Though it can't see, another new system can check container fill levels at high speeds. Developed by TapTone Package Inspection (North Falmouth, MA), the TapTone 300 can check containers made of glass, plastic, paper, and other materials at a rate up to 2000 containers per minute, says Jim Kearbey, TapTone's vice president and general manager. The system emits an x-ray beam that passes through a container. As it does so, the beam is weakened by the product in its path. An x-ray detector picks up the decrease in the intensity of the beam when it emerges from the container. The change in beam intensity is directly proportional to the container's fill level.
The TapTone 300 can also be used to count tablets in a container. When checking containers filled with relatively large antacid tablets, the system came within one of the correct count, Kearbey reports. He adds, however, that the system will probably be less accurate counting smaller tablets in quantities of 50 or less.
Due to falling equipment prices, more pharmaceutical firms are turning counting tasks over to machine vision systems. In the past, Blackwell notes, companies used sensors to count the tablets in a tray. But sensors can slow down changeovers, which are becoming more common on packaging lines. When tray configurations change, it can take a long time to replace one hard-wired sensor with another. On the other hand, Blackwell says, machine vision "lets you reconfigure your counting operation with the touch of a button."
Drug firms also use machine vision to check packages for missing or broken tablets. Older vision equipment "might have been able to see that half a tablet was missing," Fortier recalls. "But if a tablet was chipped, you had to live with it." Today, he says, machine vision is clear enough to spot tablets that are missing tiny chips.
In some inspections, the most important thing about a tablet is its color. For example, consider blister packs that contain birth control pills. The pills in an individual package are different, marked by a color scheme that shows users when to take each one. The inspection challenge: "We have to identify every single one by its color, but there is very little color variation, and the pills are very small," says Murugan Govindasamy, manager of manufacturing engineering at the Morris Plains, NJ, facility of drug maker Pfizer Inc.
For situations like this, Insight Control Systems has developed an algorithm called "contrast opposition." This algorithm is designed to help Insight's vision systems detect a misplaced or foreign tablet in a package of tablets that look almost exactly alike.
Govindasamy says there is a "very remote chance that a tablet will be misplaced. But when a line is running birth control pills and there are four different tablets coming from four hoppers, precise control is required to avoid placing a foreign tablet in a pocket."
What if a package containing a foreign tablet reaches the market? "It's a disaster," Govindasamy says. "You may even have to recall the product. No one in the industry wants to go through that process."
Some makers of inspection equipment see more color inspection on the horizon. "The cost of color is coming down to the point where it probably makes sense to [switch] to it," says Hebel, who foresees "a wholesale shift" from gray-scale vision equipment to color systems. "Increasing color precision and inspection performance delivers added value to packagers, where package color is a prime point-of-sale or point-of-consumption quality issue," he adds.
Uhlmann Packaging Systems Inc. (Towaco, NJ) is introducing two new color systems called VisioChrom (three-chip CCD camera) and VisioChrom HR. "We use a software system called Visionet, which acts as a broker," says Christopher Anderson, aftermarket sales engineer. "As long as this software is installed on at least one of our product or print inspection systems on our customers' production lines, it will gather information from other inspection systems on the line and act as a single point for getting and transmitting production information, like access passwords, time and date of records for product faults, etc. This also serves as a point for downloading and storing all electronic records from other inspection systems as well, which will then enable the entire production line and all of its inspection systems to become FDA 21 CFR Part 11 compliant."
Blackwell isn't as optimistic about the future of color. He has seen some increase in the use of color vision equipment. But even though color now costs only 15 to 20 percent more than gray-scale systems, packagers haven't been flocking to it. "Color introduces one more variable into a process that people might not want to consider," he says. "Let's say you're only interested in the dimensions of something. Why bring in color, which is just another variable you have to control?"
Govindasamy and others are evaluating an inspection machine that can't be fooled by appearances. One such system is the VisioNIR. Developed by Uhlmann, the VisioNIR system uses near-infrared technology to analyze pharmaceutical products just before the package is sealed. Designed for in-line use, the camera-based system can inspect about 200 products per second, according to Uhlmann's Anderson.
Near-infrared inspection can distinguish between tablets that look the same but have different contents. For example, Anderson says, VisioNIR can tell packagers if a tablet containing 5 mg of a heart medication has mistakenly gotten into a package of 1-mg tablets—even if the 1- and 5-mg tablets look exactly the same.
Uhlmann's NIR system performs what Govindasamy calls "analytical" inspections. "We are going to a stage where we will identify tablets by their properties, not just by visual inspection," he says. "That's the future."
Whether color or gray-scale, different vision systems on the plant floor can be linked via Ethernet networks. These linked systems can be monitored and controlled from a single station on the line. Among other things, Blackwell says, linking the machines can make it easier for operators to adjust all the different inspection settings for a new package configuration.
With vision equipment and other packaging systems linked to a network, process data can flow to a computerized management system. "This lets you produce a consolidated management report that gives you a better overview of the whole process," Fortier says. "With that kind of information, you can spot trends that help you head off problems before they occur."
When connected to a network, inspection equipment can also be accessed from a distance. So a plant manager in one part of a building can retrieve data from (or send commands to) an inspection machine in another part of the building. "From the same location, the manager can communicate with several different production lines," says Jean-Francois Lafortune, vice president of Optel Vision (Quebec City, QC, Canada), which makes network-ready machine vision inspection equipment. "This will save time in managing the lines."
Network connections can even link devices to people outside the plant. For example, vision machines made by Insight Control Systems include a feature called Snooper, which lets Insight remotely access machines at customer sites. Using Snooper, Hebel says, the company's service people can do most troubleshooting at a distance, which speeds up service and reduces equipment downtime.
Snooper also lets Insight help remote customers tailor their vision systems to meet different inspection requirements. "Without interfering with their inspection process, we can grab their images and bring them here, where we'll experiment with different algorithms until we find the appropriate package," Hebel explains. Then, with the customer's permission, Insight can load the algorithm package into the remote vision system.
Though they include new features such as network connections, machine vision systems are getting more compact. According to Heil, DVT Corp. was the first company to put all the components of a vision system in a single case. Initially, users do need a PC to set up the DVT system. But after that, the device can operate independently, using its own processor and software.
Besides being compact, the DVT system is just plain small. "You can fit the whole thing in your pocket," Heil says. Such small vision systems occupy less valuable space on the production line.
"In the past, you might have had to stake out a square-foot area for the equipment," says Blackwell, whose company continues to produce smaller vision systems. "But now we're getting [the space requirements] down to a matter of inches."
Small as they are now, Hebel believes vision systems will continue to shrink in size. This will make it easier for users to embed and integrate them into other machines on the packaging line.
Despite their diminutive size, today's small vision systems outperform their larger predecessors. Every year, for example, the performance of new Cognex vision systems improves 50 to 100 percent, says Blackwell. This improvement pleases customers, who can use the new systems to perform more inspection tasks without slowing down packaging lines.
While performance improves, people who work in the vision industry expect equipment prices to stay the same or drop. So vision inspection is a bargain that gets better all the time.
However, an inexpensive vision system is only a bargain if it meets your needs. So beware of ultracheap systems that may be costly in the long run, Hebel warns.
"Once a vision system is installed, it becomes the throttle on the yield of your line," he says. "If it's [incorrectly] blowing off half your production, you're losing yield. On the other hand, if it's missing defects that are going out to customers, you're losing customers. So you don't want to be pennywise but pound foolish."