Development of Machining Center Spindle for Realizing Elliptical Vibration Cutting

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A new cutting technology named elliptical vibration cutting has been developed by the head investigator, by which the chip thickness, the cutting force, the cutting energy, etc. are reduced remarkably and machining accuracy is much improved as compared with the ordinary cutting. The purpose of current research is to develop an elliptical vibration milling machine which can be applied to relatively large cutting loads so that the dies and molds of hardened steel can be machined. In order to realize such a machine, a unique elliptical vibration milling spindle is developed by utilizing a double-spindle mechanism. The developed machine generates circular vibratory motion of the cutting tool mechanically by rotating an eccentric sleeve with a built-in motor. The radius and the maximum frequency of the circular vibration are set to 0.5mm and 167Hz respectively. The developed machine is applied to elliptical vibration planning by clamping the tool spindle, and also to elliptical vibration end milling by rotating the inner tool spindle as well at the same time. The machining tests of hardened steel with CBN and coated carbide tools are carried out, and it was proved that the elliptical vibration cutting shows better results as compared with conventional cutting without elliptical vibration motion. A mirror surface on hardened steel with a roughness of about 0.11μm Ra was obtained by elliptical vibration planning by employing a single crystal diamond tool. Base on the above research results, a new circular vibration milling attachment was developed which can be attached to a machining center. The cutting tests were also conducted with the attachment development, and it was proved that almost the same cutting performance can be achieved.