After comprehensive consultation by Nord Drive Systems precipitated Symach Palletizers A fundamental decision: The future of palletizing machines should look decentralized. Drive units off Gear Motor and decentralized frequency converter Provide the necessary dynamic performance, open up new design possibilities for developers and lead to cost savings in a variety of ways. The ambitious engineering project will be implemented over the long term. Meanwhile, the first series of decentralized palletizers are successfully in use worldwide.
Symach palletizing machines have the special feature that they place each product individually on pallets compared to other available systems. This is achieved by a specially designed head, which allows accurate and gentle handling. The 3 to 4 m high machines are fed via a conveyor belt. Each sack, each box and each box is collected individually by a manipulator. Sacks, for example, slide against a fixed stop and are aligned by a centering unit so that the manipulator can drop them exactly at the programmed position. This allows accurate and overlapping stacking of the bags with optimum stability.
Different stack patterns and speeds can be programmed. Depending on the palletizer model, the maximum stacking speed varies between 15 and 36 bags per minute. The pallets rest on a pallet table, which is lowered during the stacking process until the defined pallet height is reached. The loaded pallet is transported via a roller conveyor to a pallet wrapping machine and wrapped in foil for onward transport.
Conversion from centralized to distributed drive technology
Palletizing machines play a key role in the production and sales process. They have to work smoothly so that product flows do not falter, and can be flexibly adapted to different goods and applications. In the past, the mechanical engineer relied entirely on central drive controls. For this purpose, mounted on the top of the machine control boxes were necessary, which took up a lot of space and caused additional costs. "The height of a palletizing machine requires the installation of a staircase to carry out any maintenance work," explains Sacha Bakker, managing director and co-owner of Dutch mechanical engineering company Symach. "The control cabinets for the servo controls hindered access. By retrofitting with compact drive units from Nord, we could easily solve this problem. "
In the new palletizers, geared motors with SK 200E frequency inverters mounted directly on the motor drive their work and control the complex movements of the manipulator and the centering unit. On the recommendation of the drive specialist, they opted for dynamic asynchronous technology instead of servo technology. The benefits of this solution are not only lower procurement costs but also greater choice for machine designers. Because asynchronous motors are available everywhere and easy to maintain, they can be easily combined with various types of gearboxes. In addition, they can be easily exchanged in Aufsteckausführung. Adding all these advantages together, palletizers equipped with asynchronous motors will result in lower total cost of ownership than servomotors.
Decentralized frequency inverters for precision and dynamics
Decentralized automation applications place high demands on drive systems. The available in graded performance classes and with various upgrade options Inverter series SK 200E allows users to select customized solutions according to their needs. With the modular frequency inverter series, decentralized applications from simple control tasks to complex positioning applications can be cost-effectively implemented. Models in sizes 1 to 4 with outputs between 0,25 and 22 kW are available. The expansion options include external braking resistors and a separate 24-V power supply for a stand-alone control voltage control.
Next Fieldbus interfaces for CAN open, Devicenet and Profibus are available also Gateways for the connection to Profinet and Ethercat networks. Interfaces for further Industrial Ethernet standards are under development. The fieldbus communication interfaces are available as external bus technology boxes - optionally with and without additional I / Os. They can be mounted directly on the inverter or remote from the machine frame or system component.
Position dynamically and accurately
The palletizing machines use the "Posicon" frequency converter function, a standard functionality of every SK 200E inverter, which enables very dynamic positioning functions with a maximum accuracy of approx. 1 / 100 of one motor revolution. For the position / position detection the compact encoder system MG from Nord is used. The distributed inverter significantly simplifies installation and wiring. The drive manufacturer supplies the motor, braking resistor and motor holding brake ready wired.
Symach uses SK 215E inverters with the additional option "Safe Stop", which provides the necessary personal protection at all times. In the palletizing machines, further features of the multitalented SK 215E are used: Sensors and actuators are simply connected to the existing I / Os of the inverter located directly in the machine. This sends this information with the normal CANopen communication to the controller. Again, cables are saved in the installation.
System transition carefully considered
During the development of the new palletizers, the decentralized drive concept was put into practice step by step. After each phase of the reengineering process, the machines underwent extensive testing. That way, you have complete control over the entire engineering. "Nord played an important role as our supplier and consultant," says Bakker. "Such a new design makes it possible to say goodbye to outdated concepts. As a mechanical engineer, we shy away from making changes, even though we know exactly that they are necessary. If you have a supplier who takes things and thinks things through, that's a great opportunity. That's exactly what happened here. For us, not only the quality of the products was decisive. Equally important are the good relationships we have built over the last few years with Nord as our global partner.
Bakker can imagine further synergy effects: "In mechanical engineering, there is a clear trend towards a well thought-out, appealing design. I would like to enforce this with us too. The level of technology is constantly converging. Every designer uses the same technologies. As a result, it is difficult to distinguish oneself as a mechanical engineer from the competition. However, a good design can make the difference when customers can choose between different makes. Also in this area, I expect our suppliers to think and support us. "
Energy efficiency is a matter of consideration
The drive manufacturer recommended the use of motors of the Energy efficiency class IE2, The IE2 engines differ in several details from the usual designs. For example, the North Germans rely on the use of more active material in the stator package with higher-quality sheet metal grades, the increase in the copper filling factors and the use of an optimized winding scheme. The energy-saving motors not only offer improved performance, but also have a longer life. The decisive factor was their reduced heat output compared to IE1 three-phase motors, which enables a more compact design of the machines.
Energy consumption played no major role in engine selection. Bakker explains: "Given that our palletizers with their installed maximum engine power of 20 kW have little potential for saving, our customers' interest in more efficient drives is not yet particularly high. The most important feature continues to be that the machine performs its tasks trouble-free. Energy saving is only a subordinate topic. But I expect a change here too soon. Energy may not be expensive enough at the moment, but that's sure to change. "