Self-Contained Vision System to Inspect Unlabelled Cans Improves Food Safety

Oct 17, 2012

The potential liability involved in mislabeling a product which might be inadvertently ingested by someone who is allergic to the ingredients is a major concern for food and beverage producers.. When you are labeling hundreds of thousands of cans at a rate of 1000 per minute, it’s a major challenge to spot a few incorrect cans or labels that were mixed in with the batch. With machines operating at this speed, 100% manual inspection is not a viable option. The only way to be sure about the ingredients is to read the character-based product code printed on the can and match it up to the Universal Product Code (UPC) barcode on the label. This operation is called bright field inspection because the metal can creates a bright background that makes it hard to read characters.

Bright field inspection is so difficult that it has only been attempted a few times by complex custom vision systems that are assembled from a camera, frame grabber board and computer. More recently, the power of much more robust and easier to apply and operate self-contained vision systems has increased to the point that they are now capable of inspecting bright field product codes at the required line speeds. Matrix Technologies has developed what is believed to be the first vision system-based bright field inspection solution, which also reads the UPC barcode and makes sure the label is fully attached to the can. This approach provides improved regulatory compliance and traceability while being much easier to configure and use and is more reliable than systems based on vision building blocks.

The bright field inspection challenge

Producers of canned foods typically make a large volume of a particular product, such as a 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. This process is called bright stacking because it begins with bright unlabelled cans. The challenge for the food producer is to make sure that each can is labeled correctly. This is important not only because customers will be unhappy if they buy a can of bean soup and discover that it is actually crème of mushroom, but an even greater concern is that they might be harmed by unknowingly ingesting an ingredient that they are allergic to.. Inspection is difficult due to the large volumes and high speeds involved as well as by the challenge of inspecting the hard-to-read product code. Additionally, private brand labels usually have the same motif regardless of product which makes it problematic to tell one product’s label from another’s.

A new approach

Matrix Technologies utilized recent advances in vision system technology to develop a better approach to bright field automated inspection. “The key to the new approach is the use of the Cognex In-Sight 5600 vision sensor to inspect the product codes against the bright can background at a speed of 1000 products per hour,” said Les Haman, Department Manager for Matrix Technologies. “In-Sight 5600 vision systems offer the same rugged design and outstanding performance as the In-Sight 5400 series, but with twice the processing speed and memory to perform inspections at line rates no other vision systems can match. In-Sight vision systems are an excellent fit for the factory environment because they are completely self-contained in an IP67 (NEMA 4) rating to withstand dust and wash down without an accessory enclosure. Cognex In-Sight vision sensors also provide a software interface that simplifies setup and operation to the point that many users allow machine operators to configure the system to inspect new parts.”

Matrix Technologies’ bright stacking solution inspects products immediately after a label is applied to a bright product. 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 stacking solution also includes a laser scanner that reads the bar code 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. A proximity sensor triggers both the vision system and the bar code reader. The vision system, barcode scanner and fiber optic sensor independently inspect each product and send pass and fail signals to the programmable logic controller (PLC) that overseas the inspection station. The pass or fail signals are buffered until the product travels to the reject mechanism. The buffer is then processed at the reject mechanisms to either allow the product to proceed or eject the product from the conveyor.

Network connectivity simplifies setup

Corporate ERP connectivity relates product codes to UPC codes. The system also utilizes Microsoft SQL Server to centralize configuration parameters and to retain failed inspection results. Setup mode leverages the ERP and SQL Server connections to ensure that the latest updates are deployed. The vision system communicates with the PLC using static outputs and communications with the PC running the over an Ethernet connection. The operator enters the new product code in the running HMI. The HMI sends the setup code to the vision system to identify the product code image it will identify. The HMI also sends the correct barcode to the barcode scanner. The HMI also provides real time image updates, inspection statistics, diagnostics and setup functions.

If you have an application for bright product inspection, please contact us today to discuss your application.


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