SPS IPC Drives Hall 3A, Booth 458
With an optimization of Idam-Torquemotoren-Series SRV eliminated Schaeffler Disturbing forces and moments of the motor, which cause conventional tilting of the axis or the clamping surface in the micrometer range in rotary axes and rotary tables. These tilts affect the surface quality of precision machining and lead to additional costs due to the required rework.
When machining with very stiff and direct driven rotary axes in ultra-precise milling, grinding and gear cutting machines, the phenomenon of short-wave surface defects can occur on workpieces. They are often recognizable by optical effects on the surfaces, such as regular stripes or shadows, or by abrasive stars on faces. These accuracy deviations of less than one to a few micrometers lead to quality problems with high-precision workpieces in mold making, lens finishing or toothing parts of the highest quality.
The cause for the deviations are pulsating axial and radial forces from the magnetic fields of the torque drive, which have a lever arm as disturbing forces and moments on the bearing effect. These relatively small loads for the bearing cause sub-micrometer axis misalignments and tilting which can be reflected in the workpiece surface. Especially with abrasive stars, the error period is usually due to the number of poles.
The phenomenon is by no means new, but today the surface qualities are so high that it can be seen on the processing tracks. In addition, the requirements for form tolerances and surface qualities in some industries have increased so much that the cost of reworking is no longer tolerated and the market demands a solution. The engineers of the direct drive specialist developed as a solution a "double" engine structure in which the disturbing forces and moments occurring in the engine are internally compensated and thus the aforementioned surface defects in ultra-precision production can be effectively avoided.
The SRV torque motors based on this principle are interchangeable with the commercially available torque motors despite the more complex design. Air gap diameters from 89 to 460 mm and magnetic heights from 25 to 200 mm are planned for the new series. The series has already been started with the size 89 mm air gap diameter.
By using the new SRV torque motors, there is no measurable entry of pulsating motor-related axial and radial forces into the machine structure. The best surfaces without optical defects and with extreme dimensional and dimensional accuracy can now be realized. At the same time, the new engines offer very high speeds of up to 14.000 min-1.