Nuremberg Rostbratwürste are intrinsically linked to the history of the Franconian city. Up until now, this unique specialty has been fed into packaging machines individually and by hand. Now, mechanical engineering experts have designed an automatic loading system that significantly increases the reliability, safety, and cost-effectiveness of the processes.
The assembly hall at mb bergmann in Hösbach, near Aschaffenburg, has been all about sausages for months. Together with designers from the stainless steel specialist Eberhardt in Lichtenau, near Ansbach, the special machine manufacturer is producing a system for testing, singulating, and inserting sausages into a film packaging machine. The design also includes automation technology and stainless steel drives from the SEW-Eurodrive portfolio. „This is a special system that doesn't exist anywhere else,“ assures Jörg Schwebel, who is responsible for hardware and software engineering at Eberhardt. „There is neither a precedent nor a comparable automation process for this. This machine is unique.“ Even the world-famous, highly sought-after Nuremberg Rostbratwurst is unique. It is said that around three million of them are produced daily. „Every sausage is a little different in terms of length, diameter, and curvature, which makes automated handling a major challenge. Especially because the sausage skins are very delicate and tear quickly,“ Jörg Schwebel points out.
Automation for greater efficiency
So far, the insertion of non-standardised natural products into the film packaging machine is entirely manual and takes place under difficult conditions. „Our customer is therefore looking for an automated alternative: In addition to the arguments of ergonomics, work simplification and efficiency, there's scrap reduction thanks to consistent handling quality,“ summarises Jörg Schwebel, explaining the reasons for the machine order.
For the bratwurst manufacturer, reliability, product safety, and greater economic efficiency are decisive factors in automating packaging processes. The requirements include that the new system can be seamlessly integrated into the existing manufacturing process. Another objective is a throughput of 1,000 sausages per minute. „We have designed the singulation and loading machine in a specific and modular way. It fits spatially and process-wise into the customer's system and replaces the previous manual line section,“ explains Jörg Schwebel, illustrating the new layout. The customer also had specific ideas regarding drive technology: „He places particular value on SEW-Eurodrive technology being installed, as he has had the best experience with it. The machine builders gladly embraced this,“ says Sarah Herberger, Solution Manager at SEW-Eurodrive, with satisfaction.
Powertrain technology without rough edges
Meat processing must be carried out exclusively at temperatures below seven degrees Celsius to effectively inhibit microbial growth. Regular cleaning also prevents cross-contamination and reduces the risk of germ transfer. Regulations such as EU Regulation (EC) No 852/2004 on food hygiene, HACCP concepts, and industry-specific standards, such as the EHEDG guidelines, mandate regular and documented cleaning processes as well as hygienic design of the machinery and components used. This means crevice-free designs, smooth surfaces, and the ability to easily clean all product-contacting components. Cleaning agents, high-pressure cleaners, and disinfectants are used in the machines, which are usually cleaned daily. In many cases, assemblies must be dismantled. These cleaning cycles lead to production-related downtimes, which cause higher resource commitment and costs with increasing duration.
The Bruchsal-based drive and automation specialist SEW-Eurodrive offers a range of drive and automation solutions in its portfolio for applications with the highest requirements for hygienic design and cleanability. Thanks to their construction in high-quality stainless steel and fanless design without corners, edges or recesses, they are ideally suited for food applications. The sausage stuffing machine, which is designed throughout with protection class IP69K, is driven by gearmotors from SEW-Eurodrive's stainless steel portfolio. These are designed so that their surfaces are particularly easy to clean. The high-quality stainless steel construction makes them corrosion-resistant and resistant to acids and alkalis. Their design allows cleaning times and resources to be minimised. They are durable, efficient, and economical. The drive and control technology of the sausage stuffing machine is controlled and driven by Movidrive application inverters and the Movi-C controller type UHX65A from SEW-Eurodrive's Movi-C automation system.
Process concept: separate, inspect, feed
The system is designed with two parallel, mirrored lines. Each of the two lines is equipped with six continuous transport lanes. Initially, the products filled in natural casings and lightly pre-cooked from the so-called sausage kitchen arrive unsorted, individually and chaotically arranged at the first processing station. The sausages are fed to the two distribution chutes via a conveyor belt. Stainless steel servo gearmotors from the PSH..CM2H.. series rotate the chutes about their vertical axis so that the six lanes of a conveyor belt are evenly filled with sausages. Level sensors monitor this: they permanently query the fill level of the lanes and control the chute accordingly. The task of this processing station is to even out the irregularly arriving mass of sausages.
The sausages lying jumbled on the conveyor belt must first be separated and aligned. This step is carried out using a step conveyor. The individual steps must be filled evenly: one sausage on each step. This line station, referred to as a dosing conveyor by the designers, is driven by a stainless steel bevel gearbox with an asynchronous motor from SEW. It is installed below the conveyor line.
The goods then reach the next stage conveyor. This conveyor line is also driven by an identical asynchronous stainless steel geared motor. This station feeds the separated and inspected sausages to the so-called indexing belt. It defines the spacing of the sausages for the gripper and is driven by a stainless steel servo geared motor. The modular system from SEW-Eurodrive allows stainless steel gear units and motors to be combined with each other depending on the installation situation and requirements. From planetary gear units, bevel or helical gear units to asynchronous and servo motors in various sizes, there is something for almost every application. To stay within the machine frame for this application, a bevel gear unit (KES..) was chosen and a servo motor (CM2H…) was attached for the dynamic and precise positioning of the belt. Each lane and each compartment of this belt must be occupied, which is monitored by optical sensors. The machine operator can check the correct occupancy status at any time via the HMI screen.
Vacuum gripper: pick and place
Ultimately, the machine will place 1,000 sausages per minute into the packaging machine. To achieve this, the indexing conveyor belt runs horizontally beneath the gripper, the final process station. The special gripper covers all six lanes and uses vacuum suction technology to pick up 56 sausages with one stroke, which corresponds to the contents of four packaging units. Traditionally, Nuremberg sausages are sealed in film in packs of 14. In this system, the designers have also provided options for packs of ten and twelve sausages. The gripper compresses the longitudinal spacing of the sausages, which is technically necessary on the indexing conveyor belt, and places the products closely together into the film trays of the packaging line. The station moves in the centre of the sausage-feeding machine between the two lines. With the mirrored gripper station, 112 sausages are therefore picked up and placed simultaneously. It is important that the gripper picks up all sausages via vacuum with every stroke. The time required for this is synchronised with the line's cycle speed. Light barriers check at the end whether all sausages have been taken from the line.
Hygienic Design Experts in Action
A special product requires select ingredients: this applies to both the original Nuremberg Rostbratwurst and the insertion machine, which is made entirely of stainless steel from start to finish. „Because the entire manufacturing process takes place in-house, all necessary components and special parts are available on-site,“ Jörg Schwebel highlights. Thanks to the collaborative partnership between special machine manufacturer mb bergmann, stainless steel experts Eberhardt, and the drive and automation experts from SEW-Eurodrive's Nuremberg Drive Office, this special machine has been created with a high degree of in-house production. „This is a very good, equal partnership,“ Schwebel emphasises. With this project, the three partners have once again demonstrated their respective expertise in the food industry. Now the machine is going to the sausage manufacturer: to Nuremberg, of course, because the sausages, with their 700-year-old tradition, may only be produced and finished within the city limits of Nuremberg according to the established recipe. The automatic sausage insertion machine is also intended to make history there.
