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| Motion control solution makes serviette machines more flexible | | Faster Printing | The track speed in serviette printing is limited by the printing technology at the moment. To increase the productivity, the start-up, setup and standstill times have to be reduced and the waste percentage minimized. The advantages which modular machines with single axis drives offer here consistently exploit a homogeneous motion control automation with system-integrated drives.
Variable format serviette printing and folding machines are a specialty of the Schnitt-Druck-Falz Spezialmaschinen GmbH in Monheim (SDF). SDF is the market leader in Europe for machines for high quality serviettes or place mats. About 80 percent of all serviette printing machines built by SDF now have eight or nine-color printing units. In addition to the trend for as high quality printing as possible, there is a tendency for smaller and smaller batch sizes. The printing motifs are moving increasingly towards short-lived topics such as special events or marketing campaigns and the variety of formats is also growing. Orders of only 20,000 packs are no longer a rarity. The result: the machines may have to be reset two or three times a day.
Therefore the start-up and setup times and the adjustment effort must be minimized and the advantages of modular machines with single axis drives exploited consistently by the automation. Together with motion control experts of the Siemens Ruhr sales region and the Siemens Application Center in Cologne, SDF developed a concept which makes the production of high quality serviettes easier and more flexible. Particular emphasis was placed on minimizing unproductive ancillary times. The latest SDF machine with eight-color printing unit and variable format folding is automated with a central Simotion D controller and Sinamics S120 drives. Micromaster MM440 converters serve as positioning and auxiliary drives. Simotion CPU and Sinamics drives form one unit, periphery and Micromaster drives are linked to the CPU via Profibus.
Ten minutes per cycle gained
The number of cables and plugs and therefore the error probability has been drastically reduced, commissioning and diagnostics are now much easier. The position control for all axes is calculated centrally so that a trace is also possible over several axes simultaneously. In addition, almost all the motors have electronic rating plates. These are read out by the Sinamics drives which enables the axes assemblies to be started quickly and semi-automatically.
The benefits of the strict data storage and communication already become evident when the machine is switched on: The drives no longer need to be referenced. Production can now begin ten minutes earlier than before every day.
Twenty nine servo drives ensure quickly reproducible settings on the machine. All machine parameters are saved by the new automation in non-volatile memories so that all the data and parameters necessary for processing an order can be stored in recipes. If a motif has to be reproduced, the appropriate printing rollers simply have to be installed and the "recipe" of the original order called. The owner can also create basic recipes for paper types and serviette formats which make the most important basic settings on the machine. Even when changing the CPU, a drive or a motor, work can continue in a short time because all the machine parameters and user programs are saved on a CF card.
Less waste
The new automation also brings technological improvements as Managing Director Andreas Rother explains: "The electronic eye can only determine the exact cutting position reliably from a minimum track speed. Because of the improved synchronization we can run up the track speed much faster and there is much less waste than before." Here, Simotion's individually definable regulating quality for every drive also plays a role because every axis develops its own existence: in the calender works for example the control must be soft whereas a hard synchronization is necessary in the printing towers.
The extremely compact Sinamics S120 double-axis modules were used for the new automation. All 29 axis drives of the machine are together just 950 millimeters wide and fit in a single switch cabinet. The actively controlled feed, a Sinamics Active Line Module, ensures an intermediate circuit voltage which is largely uninfluenced by mains feedback, constant and higher in comparison with unregulated feeds. The high regulating quality of the Simotion-Sinamics combination is therefore fully exploited and the performance of the motors increases.
The new flexibility reaches far beyond the individual machine. Simotion offers a great degree of freedom in programming and can be integrated smoothly into other automation systems. In connection with the scalability of the hardware and software of the motion control system, machine modules can be integrated more easily in the machines of other providers. Since the system is also equipped for the integration of state-of-the-art technologies, the Simotion-based automation is also very future-safe.
Ideas 3 / 2007 | |
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