Peanut flips & Co. perfectly stacked
Complex system by de Man for WURZENER GmbH: Peanut flips, rice or oat flakes - the products of WURZENER Nahrungsmittel GmbH can be found on many supermarket shelves. But before they can be transported there, they have to be stacked on pallets, wrapped and labeled. In order to make this task faster and more efficient, Wurzener invested in a complex system from de Man, in which the cartons with the products are now identified using a barcode and packed according to type in two palletizing cells on EURO pallets and prepared for dispatch.
Wurzener Nahrungsmittel GmbH is one of the most successful food manufacturers in the new federal states. With more than 100 employees, the company produces and sells snacks such as peanut flips, pretzel sticks and onion rings, but also rice, pearl barley, oatmeal, cornflakes, lentils and much more. At its site in Wurzen (Saxony), the company wanted to automate the previously manual palletizing of the product boxes. The simultaneous palletizing of different products, as well as products coming from several lines, was important. The commissioned de Man Automation + Service GmbH & Co. KG delivered a complex system consisting of two palletizing cells, several light and pallet conveyor lines, two cross transfer cars and a winding station. As the boxes are fed in at a height of approx. 2.20 metres, the feed conveyor system to the palletizing cells was suspended from the ceiling.
The different cartons are conveyed via the infeed conveyor system in the direction of the four palletizing stitches of the two palletizing cells. All cartons have a barcode on the same side, which is read by a scanner before they are discharged to the palletizing cells. If it is a product that is being palletized on one of the four palletizing stations, a discharge conveyor moves up between the rollers of the product conveyor, lifts the box and conveys it to the appropriate conveyor. This feeds the carton to the palletizing cell. The boxes can be stopped by pneumatically extendable stoppers in front of the cross conveyors, discharge conveyors or on the palletizing stitches. If, on the other hand, it is a product that is not currently selected for palletizing or if the barcode cannot be read (NoRead), the product is conveyed for manual palletizing. Here, all products not currently selected for robot palletizing are packed onto pallets by hand. In addition, the NoRead cartons are collected here and then fed to the corresponding robot via a separate feeder, specifying the correct palletizing location. Manual palletizing is also activated if one of the cells has a fault or the delivery lanes are currently full. This avoids long interruptions in the palletizing process.
Safe transport of entire layers
Both cells each have two palletizing stations on either side of the robot and two infeed conveyor lines. A lowering station takes the cartons from the conveyor stub, lowers them to a height of around 800 mm and transports them onto the layer table. The loading of the lowering station is automatically detected by a sensor. The cartons are positioned on the layer tables and prepared as a layer for removal. The robot now removes the complete layer and palletizes it on EURO pallets. For the safe transport of the layers, the robot has a fork gripper with clamping plates and a pusher. During removal, the gripper drives under the box and clamps it from above. The boxes are set down with precise positioning so that, for example, the stacking lugs of the peanut flips boxes fit exactly into each other. For this purpose, the already palletized cartons are positioned by means of an alignment unit on the gripper. The gripper was also equipped with vacuum suction cups for the bottom/intermediate layers made of cardboard stored in a magazine, the current filling level of the magazine is detected by a height sensor. The layer pad magazine has a height of 800 mm, a capacity of 400 pieces and is filled manually. A list of items that are produced in the shift according to the production plan can be stored in the operating software for each product feed. Each item is produced once. This list is gradually processed by the robot system, the products are assigned to the stitches and palletized. As soon as the scanner recognizes an item number that is entered in a stitch in the second position, this means a product change. The last products of the current batch are still palletized, then the pallet is ejected as a short pallet and palletizing of the new product begins on an empty pallet.
Palletizing without interruption
The empty pallets are stored in a pallet magazine, which has a maximum capacity of 15 pallets and is filled with an electric pallet truck. There is a buffer space for a stack of empty pallets in front of the magazine, so that a total of up to 30 empty pallets can be buffered. For a quick pallet change and a smooth palletizing process, the system has a cross transfer car that transports empty pallets from the pallet magazine to the palletizing stations via the pallet conveyor system, and a second cross transfer car that transports the packed pallets from the palletizing stations to the packaging station. When a fully packed pallet is removed, the other transfer car is ready with an empty pallet and conveys it to the palletizing station. In addition to the four pick-up points from the two robot cells, which are always immediately supplied with an empty pallet, the transfer car has a pick-up position where the finished pallets of manual palletizing are made available. In this case, no empty pallet has to be provided, as the new empty pallet can be conveniently placed with a hand pallet truck due to the conveyor technology height of 80mm. A mobile hand-held scanner is available to the employee here, with which he scans a box and thus transmits the information about the pallet (product type, number, etc.) to the system. All finished packed pallets are finally transported to the pallet wrapper via the pallet conveyor system and wrapped in film there (capacity approx. 60 pallets/hour). A chain transfer device then conveys the pallets to the labeller provided by the customer. The data required for this (e.g. barcodes on the boxes, number of products on the pallet) are transmitted to the printer from the robot cells via an electrical interface. The packaged and labeled pallets are then made available at the pick-up point for pick-up with a hand pallet truck. Up to 16 pallets can be buffered here.
The facility is surrounded by a protective fence. It encloses the two palletizing areas, the two cross transfer cars and the wrapper. The palletizing cells are separated from each other by the fence, resulting in a total of four security areas. Each area can be entered separately without affecting the other areas in the automation. Access is via protective doors that must be requested. The safety interlock with guard locking only allows the protective doors to be opened when the dangerous movements have been safely stopped. Thanks to an emergency release, trapped people can exit the cell. Areas that are not surrounded by the protective fence (e.g. at the loading or unloading point) are secured by light barriers. A muting deactivates the light barriers when the finished pallet is conveyed onto the cross transfer car. The system has three control panels, one on each of the two palletizing cells and one on the wrapper. The proven and clear de Man visualization is used as the user interface. It includes the clear representation of the system layout on a touch screen. Here the operator gets a quick overview of the status of all system parts, can have complex components displayed in more detail, has a message list quickly at hand and finds all relevant operating elements on the main screen.