Packaging cheese blocks vacuum-wrapped in film represents a major challenge for process automation. With the help of Piab’s piGRIP® configurable suction cups and high-performance vacuum ejectors, the machine and plant manufacturer TGW Robotics GmbH has developed a gripper that ensures a stable process.
When the slice of cheese is on the breakfast roll in the morning, it has already completed a considerable number of process steps. One of these is the packaging of the ready-to-sell blocks of cheese in the dairy for wholesale and retail.
TGW Robotics, a subsidiary of the TGW Logistics Group with headquarters in Wels, Austria, specializes in the construction of conveyor technology, palletizing and depalletizing systems. With 100 employees in Stephanskirchen near Rosenheim, external customers are served in addition to systems for the parent company's logistics centres.
With the customer-specific systems for cheese handling, the mature cheese block of up to 25kg is brought to the system in a ripening box on a pallet using a roller conveyor. The box is removed with a mechanical gripper. According to the further process flow at the customer, the cheese is stacked from wooden to plastic pallets in order to prepare it for further steps in a clean or white room in which the cheese is cut into slices, for example. Other customers use this step, for example, to feed various types of cheese directly into the desired quantity mix for grated cheese production.
The cheese is shrink-wrapped and thus vacuum-packed. Depending on whether the film has just been vacuumed up or this process step took place some time ago; the film is wrinkling, or the film has not been completely vacuumed; there are major challenges in automatic handling. In all cases there is a risk that the block of cheese will fall off due to leaking air or because the gripper will not be able to lift it properly.
The requirements for suction cups and vacuum generation are correspondingly high. The necessary performance and a smooth, continuous process can only be guaranteed with a high-volume flow. At the same time, the size and weight of the vacuum ejectors must be small since they are integrated directly on the gripper. Today, operating with the lowest possible energy demand is self-evident and is best met with Piab's low-energy three-stage COAX® technology.
TGW has integrated prior verification for a secure process. In the first step, an air pull control takes place. A KENOS® surface gripper checks whether the film is properly seated on the block of cheese. In addition to the described challenge in automated handling, faulty vacuuming also means packaging damage, which can lead to product spoilage. In this control step, the cheese is lifted using the KENOS® gripper from Piab, which consists of a full-surface layer of technical foam on the underside with corresponding recesses for vacuum generation. If this happens without problems, a photoelectric sensor can send a signal under the cheese block. If so, the block of cheese is moved to the further process step and can be palletized using the TGW gripper. If the block of cheese cannot be lifted by the KENOS® gripper and there is no light signal under the cheese, it is automatically rejected.
The grippers developed by TGW consist among others of configurable piGRIP® suction cups with a lip, which was originally developed for handling bags such as chip bags, and a high-performance vacuum pump based on Piab’s patented COAX® technology for multi-stage ejectors.
Maximilian Schaletzky, construction engineer at TGW explains, “The piGRIP suction cups are fantastic for our application because the soft lip can wrap around any curvature of the film. So, they can hold the blocks of cheese safely.“
"We chose to work with Piab because they were able to put together exactly the suction cups and vacuum systems that fulfil all tasks and requirements from their broad portfolio. Accordingly, we can supply our customers with an excellent system for the automated handling of blocks of cheese”, continues Schaletzky.
Sebastian Liebetrau, Key Account Manager, Germany, and the Piab specialist on site at TGW explains: “In such complex cases, we as experts in the field of gripping and lifting make a pre-selection from our extensive portfolio and then carry out trials at the customer's site to find the best possible solution.“
The gripper is rounded off by additional suction cups on level compensators on the edge, which place appropriate paper intermediate layers between the individual layers of cheese blocks as part of the packaging. This saves the employee one step and the long term physically stressful stooping over. In addition, no-one has to intervene in the machine-controlled process from the outside.
