Motor for more dynamic movement - security buffers for added peace

Four safety shock absorbers from ACE shock absorbers protect the end positions of a directly driven area motor, which was developed at the Institute for Manufacturing Technology and Machine Tools (IFW) in the production technology center of Leibniz University Hannover. The new concept of the university team is very interesting for highly dynamic machines and can, among other things, increase the productivity of machine tools.

Launched by the Deutsche Forschungsgemeinschaft (DFG) since 2010 funded Hanover project is the fundamental research into a biaxial directly driven multi-coordinate system with particular applicability in machine tools. In addition to the intensive work on the engine, the IFW team has placed among other attention to the protection of the end positions of their system. As the engineering scientist January Friederichs and Jonathan Fuchs report, it was especially true in the development phase to protect the prototypes as possible to avoid the time and cost due to unnecessary failures and not to risk delays of the project.

The two have made together with other academic staff and their professor in the past good experiences with the machine elements of ACE Stoßdämpfer GmbH, which in January Friederichs says: ". If the IFW required retarder, it turns like at ACE" Jonathan Fuchs confirms the good experience with the company. He and other researchers often use an ACE at the following Internet address www.ace-ace.de/de/berechnungen.html offered tool, through which it, inter alia, review the feasibility of new ideas with regard to the dimensioning of fitted safety dampers. Given z. B. to the moving mass, the impact velocity of the masses on the or the shock absorbers and additional acting driving forces, driving power or driving torque to be considered.

When determining the suitable solution, it was assumed that, in the worst-case scenario, a moving mass of 10 kg hits the respective shock absorber at a speed of 4 m / s with a driving force of 500 N. The combination of kinetic and drive energy resulted in a total energy / stroke of 104,5 Nm. Based on the data collected and taking into account the fact that new dampers should not be constantly installed in the event of further developments, the decision was made to install four safety shock absorbers of the type SCS33-50 EUD.

Self-safety damper build from kinetic energy

The safety bumper of SCS33 to 64 series are marked out by a unique cushioning technology, hardened guide bearing and a continuous thread. These dampers family is specifically designed for emergency deceleration and can be used in many ways by their compact design in sizes M33 x 1,5 to M64 x 2 as in Portal, conveyors or placement machine. Material and technique of self-adjusting machine elements allow 1000 load changes.

Shock body, piston rod, head and accessories consist of different machined steel, the compression spring is galvanized or plastic coated. The maximum service life is achieved when the ambient temperature exceeds or falls below values ​​of -12 ° to 70 ° C. If necessary, replacement of the damper, this is extremely easy to perform thanks to a variety of accessories and connecting parts. Combined with its compact design and the subsequent integration into existing projects without any problems. The models used in support motor are at a maximum stroke of 50 mm without fixed stop able to take 620 Nm / Cycle. ACE has in addition to these variants also further optimized damper in stock. For them, the power consumption increases to again more than 50% to 950 Nm / Cycle. But then the life is reduced to a maximum of five strokes.

Support motor can still enlarge

The special thing about it is based on the principle of permanent magnet excitation synchronous Linear motoren based surface motor is the high feed force. This solution is therefore superior to previous planar drive concepts. These usually rely on the reluctance principle to generate the feed forces in one plane. Due to their principle, such motors only generate relatively low feed forces. The motor developed at IFW also offers the innovative cross-winding technology. The windings for the individual feed directions are stacked perpendicular to one another. Since the two winding systems only influence each other slightly, this enables the use of standardized axis controllers. By using permanent magnets arranged like a checkerboard, the surface motor achieves a high power density and can therefore be used for highly dynamic machine tools.

the engine also has been optimized with regard to the typical linear direct drives disruptive forces. By means of a method for calculating the optimum geometry of the engine are significantly reduced cogging forces and Vorschubkraftwelligkeiten. In addition to reaching such an increase of the advance force. In addition, since acting dynamic loads on the drive during the machining of a workpiece, the IFW examined inter alia the behavior during milling of circular paths and pockets in aluminum workpieces and thus the influence of forces on the positioning during a machining process. This resulted in the possibility of a process-oriented analysis of driving behavior in interaction with the manufacturing process.

The transfer of findings on other sizes is now the focus of activities. Jonathan Fox has designed a larger, composed of 16 prototype modules support motor and can be manufactured thanks to the support by the DFG. By developed modularity of the engine can be, depending on the industrial requirement, different sizes of the surface motor realized. The new surface engine to produce peak forces up to 4800 N and nominal forces to 2400 N per axle. Combined with the permanent magnetic field, individual distances can be achieved regardless of the size of the surface-area motor.

According to the researchers possible applications lie in turning and milling or grinding technologies as well as in handling technology or positioning drives. Special and assembly machines with high dynamics and positioning are also suitable for use in consideration.

Just for requests from partners in these industries, the researchers are open to complete the transfer of successful basic research into practical applications.

Above: Area motor with secondary part magnets

The authors are Jonathan Fuchs, Head of components and monitoring systems at the Institute for Manufacturing Technology and Machine Tools in production engineering center of the University of Hannover and Robert Timmerberg, journalist and co-owner of Plus2 GmbH, PR and advertising agency in Wermelskirchen.