Industrially produced food places high demands on the machines and systems on which it is produced. The variety of products requires a high level of intelligence in the machine. König in Dinkelsbühl builds small pastry machines for the food industry. A particular challenge for the company was the development of a cutting machine for Maultaschen - small shells or pockets of pasta dough that are filled with vegetarian, fish or sausage meat. The prepared dough for the Maultaschen comes from an extruder. In a rolling mill, it is rolled into a dough strip, typically 600 or 800 mm wide. This strip is then cut into strands using disc knives, onto which the filling is then applied in the middle. At the start of production, the filled strands are manually threaded into the folding device, after which the process runs automatically. The cutting and sealing of the individual Maultaschen are the process steps implemented by König, which end with the transfer to the automated stove.

Synchronize knife and belt

Even at a belt speed of 15 m per minute, the cutting bridge has to touch down, move forward, lift up again, move back and synchronize again.

© SEW-Eurodrive

A newly developed tool is built into the slicer, which cuts and seals the pastry pockets in a single operation. These knives are made of stainless steel and are coated depending on the application to prevent the product to be cut from sticking. The tool geometry also prevents the filling from escaping when the dumplings are closed, as this could cause the machine to come to a standstill. The machine cuts so precisely that the filling quantity and cutting length can be matched exactly.
Cutting is tricky, because when the knife plunges into the dumpling dough, there must be no feed. The challenge is to synchronize the moving carriage with the speed of the conveyor belt.
This movement is performed by an SL2 servo linear motor from SEW-Eurodrive
is used for this movement.

Synchronizing the individual drives

The first generation of the dumpling cutter was built as a special machine. The Movidrive application inverter with the integrated IPOS positioning and sequence control system was used here. The motion coordination of the individual drives was implemented close to the axis in the inverters by means of electronic cams. An asynchronous motor with an external encoder, which drives the conveyor belt for transporting the dough, acted as the master.

The belt drives form a separate machine module in order to be able to flexibly adapt the customer-specific conditions for connecting the downstream machines via conveyor belts. For this purpose, the Movitrac LTE-B inverters (bottom row) are integrated into the network topology of the main control system via a fieldbus gateway.

© SEW-Eurodrive

The second machine generation now features centrally controlled motion coordination with a modular hardware structure. The 'synchronous cutting' machine module is based on a multi-axis servo system consisting of the Movi-PLC Power motion control system and an axis system comprising three Moviaxis servo controllers, which are controlled synchronously in millisecond intervals via Ethercat. The SEW motion controller itself acts as a fieldbus participant in the machine controller's communication network to transfer product-specific specifications such as cutting length, cutting height and cutting speed.
On the drive side, the machine module includes a servo motor for feeding the dough sheet, a servo motor for the crank drive, which performs the lifting movement of the cutting blade, and the SL2 linear drive, which guides the cutting blade synchronously with the conveyor belt.