Tula State University (Tula, Russia):

A. S. Yamnikov, Dr. Eng., Prof., Dept. “Machinebuilding Technology”, e-mail: yamnikovas@mail.ru
M. N. Bogomolov, Engineer, Post-Graduate, Dept. “Machinebuilding Technology”

When machining metals by cutting, there are almost always forced or self-oscillations. Milling is characterized by the presence of clear periodic effects on the technological system when changing the cutting teeth. At high rigidity of the system, for example, when milling the planes of the engine block, these disturbing factors are extinguished by the large static and dynamic rigidity of the system, together with high damping capabilities. On the contrary, when processing non-rigid workpieces of low rigidity, which include thin-walled bushings, periodic fluctuations in cutting forces bring the technological system out of balance and cause significant vibrations that degrade the quality of the machined surface. As practice and special studies show, this also reduces the durability of the cutting tool, sometimes to catastrophic wear. It is possible to reduce the fluctuations of cutting forces by increasing the number of teeth in the cutter and reducing the pitch of the teeth, but on smalldiameter cutters using interchangeable carbide plates with mechanical fastening this way is impossible. Returning to the high-speed milling cutters is impractical because of a decrease in milling performance and cutter life. Therefore, the article describes the development of a centering mandrel of high vibration resistance. Analyzed design features mandrels, as used in production, and described in the patent and technical literature. The proposed design of the mandrel, in which the workpiece set, rigidly basing on the short cylindrical belts at the ends of the hole and pressing the screw clamp to the base end. After basing, the workpiece is unclamped from the inside along the entire length of the free hole by elastic deformation by axial compression of an additional bushing of elastic material, located on the mandrel with clamping elements.

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