Chapter 11 Variants of high speed machining
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| 294 High speed machining arrangement and drive system are only designed for HSC or HPC milling Due to economic and technical causes, a work shift involving an adaptive bed system has not been utilized to date. There are differences in the design of shafts in machines used for HSC and HPC machining. The design of a shaft to be used in these processes has two primary difficulties. For high speeds and high stiffness, the design of the bearing causes a contradiction the bearings must be very rigid for conveying high cutting forces that occur in HPC milling with minimal deformation. Thus large bearings are used with high bearing front loads. Nevertheless, the design in question is not appropriate for operating at high rotational speeds. Due to the centrifugal forces, the shaft bearings are exposed to high thermomechanical loads. As a result, the bearings heat up, which may cause a thermomechanical instability. Due to heating, the shaft bearings are subjected to a thermal expansion that leads to an increase in preload and thus causes higher power losses in the shaft bearings. Hence this problem is solved by choosing smaller bearing diameters and lower bearing front loads for HSC milling spindles The winding system in the spindle motor represents another restricting factor fora universal shaft. The drive voltage and output frequency limit the highest speed of the spindle motor. The maximum torque is restricted to the highest current. The number of revolutions per phase constitutes an essential parameter for the voltage–current ratio. Nevertheless, high torque and high speed requirements create different demands for the number of rotations per phase. Fewer turns per phase are required by an HSC spindle in comparison with an HPC spindle in the case of the identical supply voltage [29] . As a result of eliminating the two primary difficulties in question, an economical solution to the full potential of universal machine tools can be achieved with hybrid spindles. Download 0.88 Mb. Share with your friends:
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