Case Study: Machine Vision
Food labels and printed product codes ensure product traceability, which is directly related to food safety. Current and upcoming legislation requires that manufacturers have the ability to quickly identify and locate any item in the food supply chain and trace it back to its source, and forward to its destination. To achieve this, many companies are in the process of implementing vision systems and image-based ID readers to ensure safety of the supply chain. This food manufacturer asked Puffin Automation to find a way to print the code, read the code, and reject cans with incorrect or unreadable codes.
The main challenges in creating a machine vision inspection system included: a high line rate, the radial position of the markings as the cans pass through the line, and the variation in can surface finishes. The can surface can range from dull to bright and may include water marks.
Puffin Automation designed a system that includes an In-Sight® 5600 series vision system from Cognex with PatMax®, a geometric pattern-matching technology for part and feature location. PatMax improves the ability to identify patterns in the code imprints, regardless of orientation, or variations in the can surface. In-Sight vision systems also offer the OCRMax optical character reading tool, which identifies and reads the actual characters within the code. The inspection system uses a Rockwell Automation PLC (Programmable Logic Controller), with accept/reject parameters programmed into it, and a Rockwell Automation-based servo reject kicker station, which removes improperly-printed cans from the line.
How it Works
Cans come into the inspection station in single file, and an inkjet printer prints a code on the bottom of each can. A photo eye detects each can and sends a signal to the inspection system PLC, which commands the system to acquire an image of the bottom of the can. The PatMax feature determines the radial position of the imprint, and the OCRMax system reads the code and sends information to the PLC. If the PLC indicates that a can should be rejected, photo eyes track the can so that when it reaches the servo reject kicker station it is kicked out of the line. All of this happens at a rate of 800 cans per minute.
The user interface displays the number of passes and fails, and displays the image of the last bad code. The operator can easily switch to another screen that displays index, test and home buttons for the servo reject kicker, along with alarms and error messages.
The vision inspection enclosure can be quickly adjusted in every axis to run various sizes of cans, so that it can adapt to the plant’s production change-over needs.
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To learn more about these technologies and how they work within the Verus 55 Machine Vision Inspection System, read this article in Food&BeveragePackaging.com.