Seeing double: Labelling and vision system reduces costs and errors
October 27, 2010 by John Lewis
In the past, the company manually printed, affixed and inspected the labels. "This was an intensive and exhausting job, and we had to manually inspect every label because the potential for error was high," says Joe Collins, vice-president of manufacturing and research and development for SynergEyes.
The previous labelling process began when an operator went into the company’s ERP system to pick out the SKU for the current vial and print a label. "We had to spend considerable additional time inspecting each vial to be sure we had the right label," Collins explains.
Collins looked at several alternatives for automating the labelling process before selecting code-in-motion’s automated vial labelling and verification system (VLVS). "code-in-motion was able to handle all of our SKUs and also provided a very foolproof method of ensuring that the correct label was on the lens vial," Collins says.
The system uses a Cognex DVT XS image-based ID reader that reads an in-process 2D Data Matrix barcode label, decodes the information and sends it off to an integrated printer that prints a final product label. Using code-in-motion’s patented Touch & Go rollers, the label is presented in full view to a Cognex DVT 554 vision system that rapidly inspects the printed data. The system then automatically applies the label to the vial if it passes inspection. In case of failed inspection, the operator is alerted through an integrated touch-screen PC to remove the label and print another for inspection.
How it works
Users log into the system through a touch-screen PC. Each user ID is assigned to a security group that grants access to appropriate functions, such as those for operators, supervisors or administrators. The user interface was developed from Wonderware’s In-Touch HMI. A single PC interface provides users with detailed system status and inspection results, as well as access to printer settings, camera images, system parameters and system input/output values.
Vials reach the labelling system with a 2D Data Matrix barcode in-process label on their caps applied during the manufacturing process. This barcode contains all of the information needed to produce the final product label, including multiple lens characteristics, expiration date and lot number. The operator loads the vials onto a ramp. The vials slide down the ramp and are individually released into an indexing starwheel. The first position of the starwheel is aligned with a Cognex image-based ID reader that reads the 2D Data Matrix barcode on the vial cap.
"We selected Cognex cameras for this critical application primarily because Cognex’s Intellect software gives us a much greater ability to develop and integrate multiple devices and controls into powerful scanning, printing and inspection applications," explains Dan Popovich, vice-president of operations for code-in-motion.
"From within the ID reader, we were able to parse out 2D barcode values of about 40 characters into individual data groupings, such as expiration [and] lot code, and lens characteristics, such as power and base curve. From there we could build and send out commands to a Zebra Technologies high-resolution thermal transfer printer that prints out a label specific to a contact lens," Popovich adds. "Meanwhile, we also programmed the ID reader to communicate to the vision system exactly what needs to be verified on that specific label. Using Cognex standard OCR/OCV functions, the 554 verifies, not only the presence of specified printed characters, but also their quality, where print may be too dark or light."
After the 2D Data Matrix barcode is read, a label specific for that vial is printed and dispensed onto a Touch & Go roller grid patented by code-in-motion. Labels are dispensed sticky-side down onto these rollers that are specially coated so that adhesive will not stick to them. The roller grid with label is then moved into view of the Cognex vision system that inspects the printed label while it lies flat across closely spaced miniature rollers.
The Touch & Go roller grid is another differentiating aspect of this system because of its ability to "hold" the label on the adhesive side, therefore exposing the "face" of the label (in this instance the printed side) to the camera. The entire surface of the label is exposed for inspection, while the label can be easily repositioned from one point to another.
The business benefits this patented technology provides are cost savings and reduced mislabelling risks by allowing labels to be inspected before they are applied. If an uninspected bad label were to be placed on a vial, it would require additional handling – either removing the label and then printing and reapplying a new label, or disposing of the vial altogether. Neither option is a profitable proposition for any manufacturer, regardless of the price tag their product holds. Furthermore, if a mislabelled vial fell into the supply chain, it could result in customer dissatisfaction or potentially even lead to a very costly product recall. code-in-motion’s system avoids these scenarios by inspecting before applying.
With or without scripting
Cognex DVT vision systems use predefined SoftSensors to perform specific inspection tasks without scripting. SoftSensors are software agents that extract information from selected areas in the image. SoftSensors are one of three well-defined DVT vision system configuration levels; the other two include system-level and product-level programming.
The system level contains parameters that affect the functionality of the vision system. Parameters such as communication settings and trigger mode (internal/external) are examples of system-level parameters. These define global settings that do not change between inspections.
Each of the SynergEyes contact lens types requires a specific product selection that defines a specific SoftSensor layout to match the printed label layout for that lens type. Each inspection as defined by the inspection product, or job, needs to perform a number of tasks in order to fully execute. These tasks are assigned to the SoftSensors. Cognex product-level programming is used for every inspection performed, and changes when the item being inspected changes.
Sometimes, however, applications require decisions based on information sent to or received from SoftSensors, and this can be accomplished with scripts. Scripts can perform a number of tasks, including but not limited to: accessing data gathered by SoftSensors; accessing and modifying product and SoftSensor parameters; establishing communications with external devices; preprocessing images before SoftSensors analyses them; and performing mathematical calculations.
Fast label inspection
Through custom intellect scripting developed by code-in-motion, one camera tells the printer exactly what to print and tells another camera exactly what to inspect. The entire process of scanning the 2D barcode on the cap, printing a label and inspecting that printed label takes only a few seconds.
code-in-motion programmed custom scripts in the ID reader to read and process the 2D Data Matrix barcode on the vial cap. Their routines parse a barcode value of about 40 characters into multiple commands for printing the product label. Specific commands are sent to a Zebra Technologies high-resolution thermal transfer printer that prints labels on demand.
code-in-motion also developed additional scripts to communicate the required product selection for the vision system, and the required target text values for each of the many OCR/OCV SoftSensors positioned across the label. The entire label inspection time takes only a fraction of a second. Without the SoftSensor regions, it would take much longer to read the text, because one sensor would search the entire image looking for characters.
Rejecting or applying the label
The labelling and vision verification system is controlled by an Allen-Bradley PLC, which controls and orchestrates a variety of devices – pneumatics, a stepper motor for applying the labels, and an indexing starwheel that moves vials from an input chute to a labelling position, then into an output chute.
If the label fails vision inspection, the operator is alerted through the touch-screen PC monitor. An ever-present message log updates with an inspection failure notice. Additionally, the display shows exactly which character(s) on the label did not pass inspection, or if the wrong label stock was placed into the printer. This level of detail is a great aid to the operator if and when printing issues arise. This capability is made possible through Cognex SoftSensor standard outputs and network communications integrated into the code-in-motion system.
If the label passes vision inspection, it is applied to the vial. A vacuum-drawn tamp pad picks up the label off of the Touch & Go roller grid. The tip of the label extends beyond the tamp pad and is positioned just below a rubber roller. The label is lowered into light contact with the vial so that the rubber roller is lightly depressing the label onto the vial. Meanwhile, the vial is supported by two rollers within the starwheel. The rubber roller is rotated by an accurately controlled stepper motor until the label is fully applied around the vial.
Increasing labelling quality while reducing cost
"Our new labelling and vision systems have dramatically reduced the cost of labelling our products," Collins says. "The amount of labour required both for labelling and inspection has been substantially reduced. When we first started operating the systems, we continued with 100 percent manual inspection. But it soon became clear that, thanks to the performance of the Cognex cameras, no errors were being made.
"We have operated two of code-in-motion’s labelling systems," Collins adds. "They have labelled hundreds of thousands of vials and have not made a single error. As a result of this outstanding accuracy, we have been able to reduce manual inspection to a very cost-effective and reasonable level. The result is that the total cost of labelling the product has been reduced to less than 10 percent of our previous manual methods."
John Lewis is market development manager with Cognex Corp.