The Knorr sachet packaging plant in Heilbronn, Germany packages millions of products annually such as Fix Spaghetti Bolognese, Fix Goulash and Fix Pot Roast. The plant makes ongoing improvements to its production machinery in order to meet the latest technical and food hygiene requirements. Knorr’s TPM (Total Productive Maintenance) efforts have allowed them not only to maintain their performance levels but to keep increasing them over the years. The latest step in these improvements was the installation of an intelligent machine vision system from Cognex to deliver checks of 100% of the seals on sachets produced. The vision system that Knorr deployed consisted of an In-Sight® Micro vision system, In-Sight Explorer vision software with PatMax® pattern recognition technology and a Cognex VisionView 700 visualization panel. The system was installed by aku.automation GmbH of Aalen, Germany.
The goal of 100% quality
Sporadic production errors can occur in the filling or final sealing stages of high-speed sachet production operations. However, Knorr has set an acceptable error rate of zero to maintain the highest quality. Since normal wear and tear of production machines make it impossible to make defect-free products forever, faulty items can only be excluded by checking each final product. Until recently, Knorr tried to accomplish this by assigning staff to visually examine filled trays for a few seconds and look for broken seals at the end of the production line. Although this worked well and customers had not been submitting claims for product defects, Knorr wanted Cognex’s smart vision system to ensure they would meet their goal of zero defects.
There was scepticism from the staff initially as to whether the automatic optical product inspection would be able to keep up when integrated into the process, but this very quickly turned into enthusiasm. The In-Sight vision system from Cognex was able to assess the quality of the sealed seams at breakneck speeds. In the camera’s black-and-white mode, the fine relief of the welded seams shows well with contrast between light and dark. Any material overlap or defective welds are detected immediately and the product is discharged.
Another important quality parameter is the angle the welded seam makes with the outer edge of the bag. Using PatMax pattern recognition technology, the In-Sight Micro works out the observed values, checks them against the tolerance values using an internal processor and if there is an overshoot or undershoot, it sends a not-in-order signal to the PLC, which removes that product from the process.
By cropping the pictures to only the image areas that are relevant for quality checking, the imaging experts aku.automation have managed to increase the evaluation rate to 840 frames per minute. This still leaves the vision system with sufficient capacity and the verification is reliable.
Quality, not Quantity
The In-Sight Micro gives Knorr and aku.automation a complete image processing system that they can rely on, all in a compact package of just 30mm x 30mm x 60mm (1.2″ x 1.2″ x 2.4″). Due to its small dimensions, the In-Sight Micro has an extremely wide range of fitting options so that it can be used anywhere in the production line, even in tight spaces on robots and very inaccessible places. Thanks to the VisionView user interface display, monitoring the manufacturing and inspection process is very simple. The powerful and cost-effective user interface provides password-protected user controls for setting vision tool parameters and targets regions on the factory work floor without needing a PC. This means that the employees in charge at Knorr can independently configure the system after just a short learning curve, regulating it and intervening in the event of abnormalities in the production and inspection process.
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