Self-Contained Vision System Inspects Unlabeled Cans to Improve Food Safety
Producers of canned foods typically make a large volume of a particular product, such as tomato soup, then store the cans in a warehouse without labels while waiting for orders from customers. The cans are labeled just before shipment, often with the customer’s private brand label. The cans go by at a speed of one every 60 milliseconds so conventional manual inspection is not possible. The only known effort at applying machine vision to this problem used a camera connected to a frame grabber board on a computer. Its weakness is that the specialized hardware is not designed for use in a factory environment. The cameras and frame grabber boards are susceptible to heat and dust. A considerable level of expertise is also required to set up and maintain this type of system, expertise that is typically not found in a canning plant.
A new approach
Matrix Technologies utilized recent advances in vision system technology to develop a better approach to brightfield automated inspection. “The key to the new approach is the use of the Cognex In-Sight® 5600 vision system to inspect the product codes against the bright can background at a speed of 1000 products per minute,” said Les Haman, Department Manager for Matrix Technologies. The Cognex PatMax® pattern matching tool inspects the product code. This application takes advantage of the ability of the PatMax tool to recognize a pattern regardless of its location. Rather than reading individual characters the application is configured to simply look for an image that matches the three-digit product code. A new product code can be configured simply by putting a can with the new code in position to be viewed by the vision system and positioning a rectangular box around the product code. From that point, the vision system will detect that product code even if it is in a different position or at a different angle as long as it is in the field of view. This approach is much simpler, more robust and more economical than the machine vision technology used on this application in the past.
Matrix Technologies’ bright stock labeling solution also includes a laser scanner that reads the barcode on the label of each product. A fiber optic sensor identifies labels that have not been properly glued to the can by detecting a protruding flap.
Matrix Technologies is in the process of deploying 10 of these systems to its initial customer. “Two of these machines are already up and running and they are working very well,” Haman concluded. “The bright stock labeling solutions have already proven their ability to provide accurate inspection results with virtually no downtime. Matching the images of the product codes has proven to be a much more reliable and robust solution than attempting to convert the images to characters. The existing plant personnel are able to maintain the equipment and program them to read new product codes without any difficulty. Based on performance criteria, benchmark testing, and user acceptance, this solution delivers an attractive value for bright stock inspection in the food and beverage industry.”