Printing Accuracy: Hitting the Mark
By Marie Redding
Pharmaceutical & Medical Packaging News received a question from a reader asking, “Is there a printing machine that is able to ensure 100% in-line printing accuracy?”
Suppliers readily responded. “The question sounds simple, yet the answer is complex,” says William Cuniff, sales manager, Uhlmann VisioTec (Towaco, NJ).
Many suppliers pointed out the obvious: anything less than 100% accuracy is not acceptable in the pharmaceutical or medical device industries, so finding a way to ensure 100% accuracy is mandatory. Extreme measures are taken by such companies to ensure the accuracy of every package before it goes out the door, since any type of product mislabeling can potentially cause a serious health risk.
Factors such as the type of print and the type of substrate being printed on determine the best printing method. In addition, primary and secondary packages, such as bottles, vials, blisters, cartons, and labels, all contain different types of information printed in different ways. Graphics and logos are frequently printed in color. Type must be clear. Bar codes, lot codes, expiration dates, and serial numbers are increasingly being printed digitally to meet tracking requirements, allowing products to be traced throughout the supply chain. Special coatings and other security features may also be also printed on packages.
A number of issues can arise during the printing process, relating to the printer itself.
Issues include an ink-jet nozzle becoming clogged or print smearing due to the type of substrate being used, according to Cuniff.
“When laser printing, a carton’s contrast layer or light-sensitive coating may be too thick or too thin, and cause inaccuracies. When printing with digital toner-based xerographic systems, the humidity level in the environment is one of many factors that can adversely affect printing quality,” advises Cuniff.
|An independent inspection device is needed, says Tim Lydell, CEO, Label Vision Systems (Peachtree City, GA), to catch the variety of “things that can go wrong during the printing process.”|
Tim Lydell, CEO, Label Vision Systems (Peachtree City, GA), agrees that a number of things can go wrong during the printing process. “Printers can certainly encounter mechanical malfunctions. Plates can lift or shift, ink can run out, nozzles clog, toner splatter, static discharge can cause a print head hiccup, etc. All of this can be vital when printing bar codes and unique numbers,” he says.
Designed for Ease of Use
Maintaining print integrity is important. Every letter should look exactly as intended, and bar code quality should be consistent. Some printers incorporate certain features designed to better maintain a high level of accuracy, according to Steve DiAngelis, director, Hapa North America, Hapa & Laetus (Rockaway, NJ).
DiAngelis advises choosing a printer that allows for format free operation, which will minimize changeover inaccuracies. “Electronically controlled adjustments and machine movements will provide accuracies of 0.1 mm. Avoiding mechanical adjustments and motions maintains a high level of consistency and accuracy,” explains DiAngelis. “If anything doesn’t locate properly, an error will be created, rather than the machine printing in poor quality, which is what a purely mechanical printer would do,” he says.
DiAngelis also advises simplifying the set-up process as much as possible, whether it be software-related or mechanical. “This will help ensure the printer can be se up correctly and accurately, in a way that is repeatable by different operators,” he says.
Verification is Critical
No printer alone is able to ensure accuracy. Various tools are needed to inspect and verify that all information is correctly printed and all data (such as a bar code) is readable by a scanner. Pharmaceutical companies often go to great lengths to ensure that different types of verification systems are in place, to prevent any printing inaccuracies from occurring.
“There are many excellent printers, but no printer can 100% ensure the quality of the print. An independent inspection device is required,” says Lydell. “This can be on the press, which is the best location, or on a rewind inspection system,” he says.
George Wright IV, vice president, Product Identification & Processing Systems Inc. (New York City), responds with a similar reply. “A printing device combined with an inspection system and the appropriate software is necessary,” he says. “No matter which type of printing system is used, it must contain components that are designed to inspect, verify, and validate. Even a simple printing process that uses a traditional in-line flexographic printer with a printing plate requires at least some amount of statistical process control,” advises Wright. “In digital, variable-data printing, such as with a track and trace or pedigree application, 100% automated inspection, including data validation and bar code print quality verification in accordance with ISO/IEC standards is essential,” he adds.
An increasingly popular and reliable method of automated inspection system is a vision system. It analyzes all the data being printed, and should catch any errors. Vision systems usually consist of a camera, lighting, image processor, and software that will allow users to define the parameters for inspection.
Visual inspection systems can be manual or electronic. They are designed to monitor the print area and ensure all types of print are accurate and readable.
|See the sidebar: Supplier Solutions|
“Most print applications are followed by a sensor or camera vision system that inspect not only that the print exists, but also evaluate the quality of that print, whether it is lettering, coding or marking,” explains Cuniff.
“A vision inspection system should be a one camera and one light system that will check everything in the printed area across the web,” adds Lydell.
Software is used to establish the inspection area criteria. “This eliminates the moving and sifting of cameras and lights and simplifies ease of use by the operator and saves significantly in change over and make ready,” says Lydell.
Wright offers a word of caution, explaining that not all vision inspection systems are designed to meet certain requirements of the ISO/IEC bar code print quality standards—and lighting is one example.
“The standards stipulate red light at 660 nanometers projected at 45 degrees to the target. Very few vision systems inspect using light at that wavelength and/or angle,” says Wright. “That this introduces the possibility that bar code print quality grades from a multi-purpose inline vision inspection system might vary from those of a true bar code print quality verifier, which does use a 660 nm light source at 45 degrees,” he further explains.
When a few suppliers pointed out that the initial question asked by PMP News’s reader sounded general, the reader clarified by requesting information specifically relating to printing on bottle labels.
Some verification systems are specially designed for inspecting label print, as well as bar code quality. Vision sensors can verify whether or not a bar code is legible and accurately printed. Sensors can also be used to inspect labels. A sensor will ensure a label is printed with the correct expiration date and lot code, and also aligned correctly on a bottle.
“I believe in performing 100% inspection of a label, and this is generally best done with line scan camera based technology,” says Robert Rack, president, BarCodeAmerica (Madison, NJ).
A line scan camera–based system can be used to acquire a high-resolution image of all printed items on a web, tracks them through the print run, and checks for accuracy. Any errors, such as smudges or missing characters, will be detected.
According to Rack, line scan technology allows for the inspection of extremely long labels with no loss of resolution by building an image of the entire label. “If labels have extremely small font sizes, extremely low cell sizes on 2-D codes, or narrow bar elements on ID code types, a line scan camera can be used to scale the field of view for a higher resolution. Scaling the image with more precision is accomplished by looking at a smaller area,” Rack explains.
|Printing systems often incorporate features that can help maintain a high level of accuracy, reports Steve DiAngelis, director, Hapa North America, Hapa & Laetus (Rockaway, NJ).|
Rack advises using an in-line full label inspection system with line scan based camera technology so that 100% of the label is inspected. “This includes graphics, OCR/OCV of printed characters, grading of 1-D and 2-D codes, and verification of sequential and database driven data, as E-Pedigree is implemented in the industry,” Rack says.
Simplifying the Printing and Inspection Process for Labels
In order to achieve 100% label inspection more efficiently with one system that can print and verify, Rack suggests using LED-based technology to print labels. To clarify, Rack is talking about digital printing, using LEDs for drum illumination rather than lasers. According to the suppliers own tests, extremely high-quality bar codes can be printed with this method.
“Many people are just starting to learn more about LED-based printing systems, and its capabilities exceed thermal transfer, laser, or ink-jet printing, and at a much lower cost,” says Rack. “It offers the flexibility to print labels on demand, in-house. It also has a minimal number of maintenance issues versus other printing technologies,” he says.
LED technology has the potential to change the way manufacturing operations are run, Rack believes. “If you have 15 different label lines, rather than buy 15 printers to use in-line, you can print all the variable data using one single in-line system, and integrate your high resolution inspection system on that single printer,” says Rack.
Rack cites the benefits of having a single high-resolution system in line with the single printer, saying, “Better labels can be produced in house and simpler inspection systems can be used on the individual packaging lines where product is being labeled.” A simple vision sensor or code reader would suffice on each packaging line to insure placement and ensure label correctness, according to Rack.
“It can take the place of many high-end vision systems that would need to be run by highly trained operators, and it simplifies what is needed at each labeling line,” he says.
Rack adds that an LED-based printing system coupled with a line scan camera based inspection system has the ability to provide a more efficient inspection process because it can inspect everything on a label including graphics, bar codes, and other fixed and variable data as it is being produced. “Full, on-demand color label printing in-line, using LED technology, will be the wave of the future for medium speed labeling lines,” he predicts.
Important to note, however, is that an LED-based system can’t print as fast as conventional flexographic and plate based technologies. “It’s not fast enough for every pharma company, but it would work for about 85% of the lines on the market,” says Rack. “The major benefit is that it doesn’t require the addition of another printer to add variable data, bar codes, expiry, and other info in a secondary operation or in-line on the labeler. This is necessary when using the other printing technologies,” Rack adds.