Renovation of vision system DOC Cheese

Quality first

'Unjustified approval or rejection of cheeses'. This had recently been occurring more and more frequently at DOC Cheese because the existing vision system used to perform quality checks in the shipping department was becoming obsolete. Making adjustments to the system was becoming increasingly difficult, as was obtaining service. This was therefore the reason DOC Kaas called in EKB to upgrade the existing inspection system to the latest technology. After all, in order to produce high-quality cheeses at a good price, nothing can be left to chance.

"Vision technology to check the quality of our cheeses before they enter the ripening process is not new to our organization. What is new, however, is the fact that we have recently had to deal more and more often with incorrect rejection or approval. This in fact requires more human intervention," says Arjan Barelds, Warehouse Team Leader at DOC Kaas. "Especially with the thousands of cheeses that leave the factory here every day, you want to be able to trust the technology almost blindly. So it was high time to renovate the existing inspection system and upgrade it where possible, so that it can last for years again. That's why we engaged EKB. EKB's facility in Houten focuses, among other things, on manufacturing new, high-quality in-line inspection systems and/or upgrading existing vision systems."

Custom

Tim Oosterom, Vision System Engineer at EKB says: "For all our customized vision solutions, we always start by performing a 'quick scan'. This includes looking at the product (read: cheese), checking whether the product can be inspected properly and mapping out the customer's requirements and wishes. Based on the findings, a customized vision system can then be developed, or as with DOC Kaas, the entire software of the existing system can be renewed, with a plan to upgrade the hardware at a later stage."

Background

DOC Kaas is a subsidiary of one of the largest dairy concerns in Europe, the German DMK Group. At the Hoogeveen facility, a team of 280 employees produce pasteurized block cheese and natural cheeses for the world market 7 days a week, 24 hours a day. These include cheeses with standard fat classes such as 20+, 30+, 45+, 48+ and 50+, as well as subspecies such as Maasdam and Emmenthaler. For the production of all these cheeses, raw milk is delivered daily to the Hoogeveen factory from Dutch and German farmers. Quality samples are taken both at the farmer's premises and upon entering the factory. On the one hand, this is to check whether antibiotics are present and, on the other hand, this is to determine whether the milk is chemically and bacteriologically completely in order. If antibiotics are found in the milk, the entire batch is unusable. If the samples are okay, then the milk is stored refrigerated in milk tanks on the premises at 4°C. Furthermore, this plant is regularly supplied with rennet, lactic acid and salt, the other basic raw materials for cheese making. The remaining milk whey is processed at our own whey processor Wheyco. The water released in the process returns to DOC Kaas via a "polisher" to be used as process water.

Production Process

In the pre-factory, raw milk is made into cheese milk by skimming it. Then the cheese milk goes through the thermizer to the cheese factory for pasteurization. Then the milk enters the curd maker. After a short rest period, the lactic acid, rennet and other additives can be added. When the resulting mass has the right jelly-like structure, the mixture is ready to be made into cheese. Making cheese is a process of hours, depending heavily on the batch size. The natural cheese then goes through the brine bath to a natural warehouse with conditioned air for further ripening, and the foil cheese is vacuum packed after the brine bath and further ripens in a refrigerated warehouse.

Quality assurance

The main requirement when manufacturing the cheeses in this factory is to achieve the most consistent product possible. A product free of contamination, free of damage, no open crust and free of wood splinters. The vision system for the final check is therefore set up in the shipping department at DOC Kaas. Barelds: "If we were to perform this check earlier in the process, the cheese would come out of the brine bath clean, for example, but all kinds of things could still go wrong during each treatment along the way. At the place we have now selected for the inspection system, this is not the case. Nothing more can happen between here and the customer."

Inspection System

Oosterom explains: "The inspection system mentioned above works on the basis of camera images. With these images, quality deviations can be viewed. In this cheese factory, for example, the top and bottom of the cheese are checked, as well as the government mark. DOC Kaas uses this system to check, among other things, whether white, black or brown spots are visible. The presence of such spots may indicate maintenance residues, drops of cheese coating, wood splinters or other types of damage. All these blemishes, inventoried beforehand by our people, are programmed into our software so that the system later recognizes them fully automatically."

Control

The production line described above is completely controlled by a PLC, which communicates via a Profibus network. All installed equipment, such as the IPC, the SCADA systems installed along the production line and the vision system in the expedition communicate with this MES layer. As soon as a cheese in the expedition passes the distance sensor, the line camera with illumination is switched on fully automatically to record images of the passing product. Because one image is recorded per line, you have many images per second. Once the line image is complete, the image is loaded into the IPC. These incoming images are evaluated in the IPC using the software algorithm entered beforehand and developed in-house by EKB. If a deviation is detected, a signal is automatically sent to the PLC control system and the cheese in question is ejected from the production process in a few seconds and sent to the buffer conveyor. An operator on the line then visually checks whether the ejected cheese has to be approved or rejected. If the cheese is wrongly rejected then the operator puts the cheese back on the belt and it can continue on its way. Oosterom: "Only one software algorithm was developed for all the different types of cheeses in this process. One difficulty with the conversion of the existing system described above was the obsolete lighting. Because work is done with a line camera, only the relevant line needs to be illuminated per image. With the current lamp with a high light intensity, this was difficult because the light is more diffused than desired. Therefore, during the renovation, we chose to adjust the camera setup somewhat. If the lighting is renewed soon, this problem will be overcome."

Finally

Barelds explains, "As a result of the aforementioned renovation, we managed to significantly improve the consistency of the production process in a relatively short period of time at low cost. As a rule, an approval of 98% is now effortlessly achieved with most of the cheeses produced. And with the older cheeses, with more color difference, an approval between 95 and 97% is acceptable. The optimized inspection system has now been made so intelligent that a cheese, which was previously ejected by the system and returned to the belt after the visual inspection by the operator, is indeed approved on a second inspection."