As labelling requirements get more complex, inspection technology must keep pace. Installation of today’s state-of-the-art systems can also provide a boost in efficiency.
A pharmaceutical packaging line presents a challenge for vision system applications because of the need to select exactly the right label among the dozens of possible alternatives needed to meet differing languages and regulatory requirements around the world.
When one pharmaceutical manufacturer installed a new packaging line, it decided to upgrade the vision system to Cognex In-Sight 5100 and 5600 systems, which use optical character recognition and optical character verification (OCR and OCV) to read characters on the label and compare them with the correct sequence. This approach reduced the false reject rate to 0.5%, making a substantial contribution to improving the first pass yield (Quality) and consequently the overall equipment effectiveness* (OEE) by 200%.
The packaging line used previously in this application was a linear machine with hot stamp pressure-sensitive printing and an image comparison vision system. This vision system had difficulty in matching ideal to actual images, which led to a high false reject rate. The vision system used in the past rejected 25% of good packages. This high false reject rate played a major role in the line’s disappointing OEE. The vision system also took a considerable period of time to set up for new labels.
The pharmaceutical manufacturer began looking at alternatives for improving the line. The company developed a rotary labelling machine using thermal transfer printing that offers higher availability and performance. For help in improving the vision system, the company called upon Wilfredo Jiménez and Jesus Otero from WJ Automation & Integration (WJAI) in San Juan, Puerto Rico.
‘When I first got involved in the project, the company was working with a machine builder to design two rotary label machines,’ Jiménez said. ‘They needed to inspect every aspect of a very complex label with near 100% accuracy. My contact told me about the problems with the previous system and asked if we could help. We accepted the challenge. The first step was finding a vision system that could accurately identify and verify the many different labels. We picked Cognex In-Sight 5100 and 5600 vision systems because they are fast, accurate, easy to programme and compact enough to fit easily within the available envelope of the machine.
‘One of the problems with the previous system was that it used a separate camera, framegrabber and computer which were connected together by cables,’ he explained. ‘The interconnections generated a lot of noise, which was one reason for the poor accuracy of the vision system. The In-Sight 5100 and 5600 avoid this problem because the complete vision system is self-contained within a single housing.
‘Both Cognex vision systems are very fast, providing a 100 millisecond inspection cycle, which is well under the cycle time of the machine.’
The In-Sight 5100 vision system acquires up to sixty 640 x 480 pixel full frames/second with high quality 8-bit images. The In-Sight 5600 takes 640 x 480 pixel images at rapid speeds.
System programming
Depending on the specific label that is used, information can appear on the right side, left side, or on both sides of the label. The left side of the label normally has a maximum of three lines of text with a maximum of 15 characters on each line. The right side of the label normally contains the Pharmacode, also known as Pharmaceutical Binary Code, a 1-D barcode standard used in the pharmaceutical industry as a packing control system. Some labels also have 2-D barcodes, which could be on either side of the label. A 1-D barcode that defines the lot also appears across the bottom of each label. This means that a relatively large field of view of 4 inches (10.16cm) wide and 2.5 inches (6.35cm) high must be read to verify the label fully. The labels are also very glossy so they have a tendency to create reflections that can detract from image quality. Another inspection required was to check that the bottom side of bottles are properly printed.
A close up of an In-Sight camera
WJAI addressed this challenge by dividing up the field of view into left, right and bottle bottom and addressing each section with a separate vision system. The company used a Cognex In-Sight 5600 for the left side, an In-Sight 5100 for the right and another In-Sight 5100 for bottle bottom. The left vision system has a field-of-view of 1 inch wide by 2in high (2.54 x5.08cm); the right system has a field of view 1.5in (3.81cm) wide by 2in high; and the bottom vision system has a field of view of 2in wide by 2in high. A diffused light was used and the lighting angle chosen to minimise reflections.
WJAI used Cognex In-Sight Explorer software to programme the cameras to read the labels. On the left hand camera, Cognex OCRMax was used to read the three lines of text and compare them with the expected result. Cognex OCR/OCV tools handle low-contrast characters as well as confusing or unevenly spaced characters. Cognex IDMax code reading tools read the barcodes. IDMax handles degradation in code appearance to deliver consistently high read rates. The machine production rate could be tripled from its current 100 bottles/minute without increasing the vision system speed.
Integration in-line
WJAI configured the vision systems to communicate with the Allen-Bradley programmable logic controller (PLC) and human machine interface (HMI) software that run the machine. When running a new batch of labels, the operator first selects the type of label in the HMI, which in turn informs the vision system of the text and barcodes that should be on the label and their position. This integration eliminates the need for setting up the vision system when changing from one type of label to another. The PLC also sends a signal that the label is in position ready to be inspected. After inspecting the label, the vision systems provide the results to the PLC and HMI.
Bottles that fail the inspection automatically go into a bad parts bin for manual inspection and repair. The operator can see images from the camera in real time on the control window, which makes it easy to resolve any issues.
The new vision system took only one week to validate compared with three months for the previous system. It exceeded the pharmaceutical manufacturer’s expectations by providing a false reject rate of only 0.5%. It also helped to improve the performance (standard vs. actual) of the packaging line by smoothing the progress of changing over from one type of label to the next. These improvements in first pass yield and availability played a major role in the dramatic improvement in OEE, which put the pharma manufacturer among the highest performers in the industry.
Footnote: *The overall equipment effectiveness (OEE) is the ratio of the fully productive time to the planned production time and can be calculated as a product of its three contributing factors: OEE = Availability X Performance X Quality. This type of calculation makes the OEE a severe test. For example, if all three contributing factors are 90.0%, the OEE would be only 72.9%.
The generally accepted world-class goals for the three factors are: Availability: 90.0%; Performance: 95.0%; and Quality: 99.9%, which yields an OEE of 85.0%. Worldwide studies indicate that the average OEE rate in manufacturing plants today is around 60%.
