Abstract
The paper analyzes the structure of technological fixtures for the positioning and fixing of large-sized thin-walled pyroceram shells as a factor affecting the dynamic characteristics of the grinding system. The solution to the problem of ensuring the dynamic stability of the «mandrel-workpiece» subsystem is necessary to increase the efficiency of shell machining in present conditions. Studying the vibrations frequency spectrum of the technological system during grinding has made it possible to determine their sources. The magnitude and frequency of vibrations depend on the mandrel structure - the clamping fixture. The study results are the requirements for a new mandrel structure, considering the dynamic stability of the technological system.
Highlights
Thin-walled shells are a component of rocket and aviation technology
Even at the finishing stage of machining the outer surface, the basic inner surface of the workpiece, obtained after its final grinding, has a significant error - up to 0.2 mm [1]. Such conditions of basing and fixation determine the values of natural frequencies of the «mandrel-workpiece» subsystem vibrations and influence the level of forced and self-excited vibrations
Non-synchronous spectrum components Subharmonics resulting from the grinding wheel rotation; natural frequencies of the «spindle assembly – mandrel - workpiece» subsystem Frequencies corresponding to the operating frequency of the grinding wheel and the lowest natural frequency of the shell Superharmonics, which occurs during the grinding wheel rotation Superharmonics, which appears due to changes in the shape of the grinding wheel
Summary
Thin-walled shells are a component of rocket and aviation technology. Products have a complex profile (paraboloid of rotation), large dimensions with the following parameters: diameter of 200-500 mm, length of 1000-2000 mm, wall thickness of 5-6 mm, and are made of fragile, difficult to machine material (pyroceram, ceramics). The shell is positioned and fixed in a fixture, i.e. a mandrel In this case, even at the finishing stage of machining the outer surface, the basic inner surface of the workpiece, obtained after its final grinding, has a significant error - up to 0.2 mm [1]. Even at the finishing stage of machining the outer surface, the basic inner surface of the workpiece, obtained after its final grinding, has a significant error - up to 0.2 mm [1] Such conditions of basing and fixation determine the values of natural frequencies of the «mandrel-workpiece» subsystem vibrations and influence the level of forced and self-excited vibrations. Non-synchronous spectrum components (environmental noise; low-frequency spectrum of vibrations of other elements of the technological system) Subharmonics resulting from the grinding wheel rotation; natural frequencies of the «spindle assembly – mandrel - workpiece» subsystem Frequencies corresponding to the operating frequency of the grinding wheel and the lowest natural frequency of the shell Superharmonics, which occurs during the grinding wheel rotation Superharmonics, which appears due to changes in the shape of the grinding wheel
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