Drives & Controls April 2022

41 www.drivesncontrols.com April 2022 CONVEYORS AND MATERIAL-HANDLING n types are particularly susceptible to these problems. “You can minimise the problem of the bags deforming by putting a special coating on the affected surfaces,”Schmachtel says.“But that wears off over time and contaminates the production environment. An increasing number of companies are even banning such coatings from their production halls, so our customers are sure to appreciate a product transport solution that is virtually wear-free.” To prepare for the challenges that lie ahead, Wolf decided to develop a new top-closing machine. Combined with one or two FFS machines and a dosing system, the top- closing machine had to be capable of producing, filling and sealing up to 80 bags per minute for a single variant. For a duplex variant, the goal was up to 130 bags per minute. A further aimwas for the machine to be able to handle a wide range of bag types, materials and closure methods, with as little effort as possible during changeovers. This would allow plant operators to react flexibly to market requirements and to choose closure options such as labels, gables, clips or rider tops. To do this, bags that have been formed, filled and sealed by the FFS machine must be transferred to the top-closing machine’s transport system, which carries them to various processing stations. In the case of a block bottom bag with a label closure, these stations form the top, press it, cut it, seal it and fold it over to make a compact bag without any unnecessary space at the top. Finally, the folded top is attached to the block-shaped bag using a label. Wolf tested several decoupled transport systems for factors such as payload capacities, shuttle handling and supplier support. In the end, the company chose B&R's long-stator linear-motor-based SuperTrak system. Unlike a chain-driven conveyor with fixed couplings, this system transports the bags in cartridges mounted on independently controlled shuttles. The shuttles can pass through the top-closing machine’s processing stations independently of the rate at which they leave the FFS machine. “Since the bags are carried through the machine in the cartridges, there are no shearing forces on the bottom of the bag,” Schmachtel reports.“Each shuttle can be programmed and controlled individually. This enables us to tailor the movement profiles to different packaging types and contents, which allows us to produce more efficiently and gently than ever before.” The shuttles can also travel backwards. Wolf's designers used this capability to incorporate a vibratory movement into the top-closing machine.“This eliminates the need for a separate station that vibrates the bags to compress bulk material,”Schmachtel explains.“The space that is saved can be put to other uses. The vibration process no longer has to be completed within a certain timeframe, so it can be implemented more gently and/or more effectively. Users can also implement different movement profiles with custom vibration functions for different product variants.” Increased output The programmable movement profiles give designers more freedom in arranging the processing stations, and they can skip or add stations as needed. One way to take advantage of this is to double up time-critical stations to boost output or hit target cycle times. You can do this without needing to have two of every other station as well, as you would with a fixed-chain conveyor system. The programmable movement profiles also make it possible to process multiple packaging types or materials on the same line, simply by of adding or skipping processing steps for certain bags. This makes the track- based top-closing machine an ideal partner for Wolf’s flexible FFS machine. Schmachtel points out that the track systemmakes it possible to boost output or produce variants with minimal added costs.“It also makes it easier to integrate into the user’s production line, and the customisable movement profiles give us more freedom with regard to where we position the transfer stations for the FFS machine or packer. The entire system layout is really easy to adapt to the situation on site.” The modular design of the guide rails gives machine-builders extra freedom when designing machine layouts.“We can easily lengthen or shorten the top-closing machine and adjust the number of shuttles as required,” says Schmachtel.“The flexibility to change the overall direction of movement makes it easy to adapt to new requirements.” The first new-generation machine built by Wolf incorporates an oval SuperTrak system, consisting of two 180-degree curved segments and six straight segments, each 1m long. The curved segments can also be used for processing. Wolf has built in sufficient space reserves to add more stations in the future. B&R offers a simulator tool that can check in advance whether a track design, and any future expansions, will meet target cycle times.“We were able identify just the right number of shuttles and parallel processing stations to handle a respective bag type,” Schmachtel reports.“That way we can avoid unnecessary investments and minimise development risks.” The high efficiency of the system also cuts running costs. The only things that need to be moved are the shuttles and bag cartridges, with much lower masses than permanently coupled transport systems. Less power is needed for acceleration, and braking energy is recovered and used to accelerate the shuttles. The potential of the new transport technology has givenWolf ideas for future innovations.“We have only begun to explore the possibilities of SuperTrak,”says Schmachtel. “It would be possible, for example, to have two shuttles grip a bag and open it as it travels between stations or to combine shuttles for an increased payload. Things like that open up exciting new possibilities to design ground-breaking new filling and packaging machines.” n Wolf developed its top-closing machine for high performance using a long-stator linear motor system. The transport system moves bags individually to the processing stations.