Analytical Modeling of Chatter Stability in Turning and Boring ...

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Fig. 1 „a,b… modal test setup and „c,d… frequency measurement setup the stable and unstable cutting zones, and absolute stability limit. In order to confirm the absolute stability limit prediction, a fine variation of the depths is used. Also, the effect of the nose radius on the absolute stability limit is considered in the experiments by using inserts with different radii. A conventional manual lathe is used during the experiments, which allows for specific spindle speeds, i.e., 700 rpm, 1000 rpm, 1400 rpm, and 2000 rpm. A modal test setup is used to measure the transfer functions of the workpiece and the tool �Figs. 1�a� and Fig. 2 Triangular inserts used during tests with radii: „a… 0.4 mm, „b… 0.8 mm, „c… 1.2 mm, and „d… the round insert with a 12.6 mm dia; „e… regular insert seat and „f… ground insert seat for desired rake and inclination 1�b��. The modal test setup consists of an impact hammer, an accelerometer, and a data acquisition system. The data are collected and analyzed by CutPro ® �8�. In addition, a sound frequency measurement setup was prepared in order to measure and verify the chatter frequency �Figs. 1�c� and 1�d��. The setup consists of a microphone and a data acquisition setup. The data are collected and analyzed by LabView ® �9�. As a second check, the finished surface is observed by the naked eye for chatter marks in order to verify the unstable cutting operation. In experiments, coated carbide triangular inserts with 0 deg rake angle are used. There are three inserts having different nose radii, i.e., 0.4 mm, 0.8 mm, and 1.2 mm, as can be seen in Figs. Table 1 Parameters used in the verification of flexible tool turning chatter experiments Side edge cutting angle 10 deg Rake angle 5 deg Inclination angle 5 deg Insert nose radius 0.4 mm Cutting force coefficients, Kf 800 MPa Cutting force coefficients, K r 128 MPa Natural frequency of the tool 1100 Hz Stifness of the tool 1.2�10 7 N/m Damping ratio 0.015 734 / Vol. 129, AUGUST 2007 Transactions of the ASME Downloaded 16 Aug 2007 to 193.255.135.9. Redistribution subject to ASME license or copyright, see http://www.asme.org/terms/Terms_Use.cfm
Fig. 3 „a… Transfer functions of the tool and the workpiece, „b… chatter frequency measurement result at 2000 rpm experiments, and „c… chatter test results for model verification and the surface finish of a stable versus unstable cut 2�a�–2�c�, respectively. A round insert �Fig. 2�d�� is also used in order to verify the nose radius model. Also, a feed rate of 0.08 mm/rev was used for all tests. In order to avoid eccentricity and to cover a wider range of angles in a practical manner, insert seats with different angles were ground and used under the inserts during the cutting tests �Figs. 2�e� and 2�f��. The side edge cutting angle in the turning experiments is set by rotating the tool holder from its clamped end. The workpiece material used during the tests is a medium carbon steel �AISI 1040�, and an existing orthogonal database was used for the cutting force coefficients. The orthogonal database was generated by using orthogonal tube cutting tests. The cutting Journal of Manufacturing Science and Engineering AUGUST 2007, Vol. 129 / 735 Downloaded 16 Aug 2007 to 193.255.135.9. Redistribution subject to ASME license or copyright, see http://www.asme.org/terms/Terms_Use.cfm
Page 1: Emre Ozlu Erhan Budak e-mail: ebuda
Page 5 and 6: Fig. 6 „a… Transfer functions o
Page 7: 5 Conclusions Three cases of chatte

Analytical Modeling of Chatter Stability in Turning and Boring ...

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