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1 33 Journal of Technology, Vol. 30, No. 1, pp (2015) * CNC Z EFFECT OF TOOL MATERIAL ON THE MACHINING STABILITY OF A MILLING MACHINE Yung-Jun Chen Kung-Da Wu Chun-Wei Lin Wei-Cheng Shih Jui-Pin Hung* Graduate Institute of Precision Manufacturing National Chin-Yi University of Technology Taichung, Taiwan 41170, R.O.C. Key Words: machining chatter, machining stability, tool material. ABSTRACT Chatter vibration induced by self-excitation during the chip generation process may produce poor surface quality and cause damage to the cuter and machine tool. To avoid the occurrence of chattering, machining operation * hungjp@ncut.edu.tw Corresponding author: Jui-Pin Hung, hungjp@ncut.edu.tw

2 34 was performed under poor conditions with more conservative consideration in tooling selection, but the productivity and efficiency of material removal could be reduced. It is therefore important to establish the machining criteria for achieving optimum material removal rates with the highest machining stability. On the other hand, according to the machining mechanic, chattering is eventually caused by the dynamic interaction between the spindle tool system coupled with machine frame structure and the cutting process. Besides, the machining behavior can be characterized in terms of the stability lobes diagram. Therefore the prediction of machining stability is not only of great importance for the design of a machine tool toward high-precision and high-speed machining, but also can provide information for selecting adequate cutting conditions to achieve stable machining without chattering. This study was aimed to present the criteria for the evaluation of the machining stabilities of a milling machine tool. For this purpose, we first conducted the vibration tests on the spindle tool to assess the tool tip frequency response functions along the principal modal axis. And then, based on the orientation dependent stability analysis model proposed in this study, we evaluated the variation of the dynamic characteristics of the spindle tool and the corresponding machining stabilities at a specific feeding direction. Following the stability analysis model, the limited axial cutting depths for stable machining within the whole interested feeding directions were obtained. Current results demonstrate that the stability boundaries and limited axial cutting depth of a specific cutter were affected to vary with the changing of the feeding direction and the feeding height of spindle head. It was also noticed that the tool material affect the dynamic characteristics and machining stability of the spindle tooling system. It is believed that realizations on the variations of the machining stabilities of a spindle tooling system within the entirety of feeding directions can provide a valuable reference for the selection of machining conditions in tool path planning. (machining chatter) Tlusty [1-3] Tobias [4] Altintas and Budak [5-7] (dynamics of machine tool structure) (cutting process dynamics) [8, 9] Choi Lee [10] 50% [11] Minis [12]Altintas [13]

3 35 Hung [14, 15] CNC 1. [5] F x F y xy (1) F x 1 axx axy x 1 zkt F { Ft ( )} zkt[ At ( )]{ ( t)} y 2 ayx ayy y 2 (1) axx() t axy () t [ At ( )] ayx() t ayy () t (2) st st st { rs ( )} [ Gs ( )]{ Fe } ;{ ( s)} (1. e ) GFe { } (2) (3) st 1 st st { Fe } zk 0 t[ A0](1 e ) Gs ( ){ Fe } (4) 2 Z n (5) (6) 2 (1 ), 2 tan (5) R 2 1 zlim k k NKt 60c n, k lobes(0,1, 2,... N(2 k ) 2. (6) [16] G(s) xy mi X MT Y MT (xy)(uv) (4) (7) det([ I] [ ( iw )]) 0 (7) OR c (8) (9) uv Z n (7) OR (8) [ ] [ A ][ ] (8) OR 0 uv auu auv [ A 0 ] (uv) avu avv uu vu [ uv] (uv) vu vv xx xy [ xy ] yx yy ( = 0) XY (9) x F (9) xx xy x y yx yy Fy Gxx() s Gxy () s Gs () Gyx() s Gyy () s (4) (3) uv XY uv (10) u cos sinx u x [ R] (10) v sin cos y v y

36 Y feed(v) 1 Y MT(y) m xy i α θ X feed(u) Y axis Xmin 90 30 25 20 15 180 10 0 X axis Feeding angle X MT(x) 270 (a) (b) K1ξ 1 K2ξ 2 Cruve A Cruve B (a) (b)

xy ][ R] (13) (13) uv Z lim Z lim Z lim = Z() 1 FRF TC-510 CNC 10 mm 2 ( 45295545 mm) 1. X Y 3 X X Y X X Y G xx G yx Y G xy G yy 3 2.

4 36 Y feed(v) 1 Y MT(y) m xy i α θ X feed(u) Y axis Xmin X axis Feeding angle X MT(x) 270 (a) (b) K1ξ 1 K2ξ 2 Cruve A Cruve B (a) (b) Z lim = Z(θ) 2 TC510 CNC XY uv (11) Fu F x F x F 1 u [ R] [ R] F v F y Fy Fv (11) (9)-(11) (12) (13) u xx xy F 1 u [ R] [ R] v yx yy Fv (12) 1 [ uv] [ R] [ xy ][ R] (13) (13) uv Z lim Z lim Z lim = Z() 1 FRF TC-510 CNC 10 mm 2 ( mm) 1. X Y 3 X X Y X X Y G xx G yx Y G xy G yy Hz (X ) 932 Hz (Y ) X Y μm/n m/n 954 Hz (X ) 996 Hz (Y ) X Y μm/n μm/n X Y Hz ( Hz) 5 1. X Y X Y Z lim (AL 7075) 6

5 37 6 XY Limited depth mmhss 10 mmwc 7 5 Z X Y X mm Y mmx mm Y mm (AL 7075) 2. X-Y G xx G yx G xy G yy X-Y 7 ( 45 mm ) (5.5 mm) (7.2 mm) 5.5 mm 120 (4.5 mm) mm 4.5 mm (AL 7075) X-Y 545 mm ()295 mm () 45 mm () 8 8

6 38 1. (AL 7075) 2. (AL 7075) 3. X Y 4. Z XY 8 () 45 mm () 545 mm () () 1. Tlusty, J. and Polacek, M., The Stability of the Machine Tools Against Self-Excited Vibrations in Machining, Proceedings of the ASME International, pp (1963). 2. Tlusty, J., Dynamics of High-Speed Milling, Journal of Engineering for Industry, Vol. 108, No. 2, pp (1986). 3. Koenisberger, F. and Tlusty, J., Machine Tool Structures-Vol. I: Stability Against Chatter, Pergamon Press, Englewood Cliffs, NJ (1967). 4. Tobias, S. A. and Fishwick, W., The Chatter of Lathe Tools Under Orthogonal Cutting Conditions, Journal of Engineering for Industry, Vol. 80, PP (1958). 5. Altintas, Y. and Budak, E., Analytical Prediction of Stability Lobes in Milling, Annals of the CIRP, Vol. 44, pp (1995). 6. Budak, E. and Altintas, Y., Analytical Prediction of Chatter Stability in Milling-Part I: General Formulation, Journal of Dynamic Systems, Measurement, and Control, Vol. 120, No. 1, pp (1998). 7. Budak, E. and Altintas, Y., Analytical Prediction of Chatter Stability in Milling- Part II: Application to Com-

7 39 mon Milling Systems, Journal of Dynamic Systems, Measurement, and Control, Vol. 120, No. 1, pp (1998). 8. Tobias, S. A., Machine-Tool Vibration, Blackie & Son Ltd, London, UK (1965). 9. Tlusty, J., Manufacturing Processes and Equipment, Prentice Hall, NJ (2000). 10. Choi, J. K. and Lee, D. G., Characteristics of a Spindle Bearing System with a Gear Located on the Bearing Span, International Journal of Machine Tools and Manufacture, Vol. 37, No. 2, pp (1997). 11. BIG-PLUS Tooling System, com/ spindledamage.html 12. Minis, I. and Yanushevsky, R., A New Theoretical Approach for the Prediction of Machine Tool Chatter in Milling, Journal of Engineering for Industry, Vol. 18, pp. 1-8 (1993). 13. Alintas, Y., Shamoto, E., Lee, P., and Budak, E., Analytical Prediction of Stability Lobes in Ball End Milling, Journal of Manufacturing Science and Engineering, Vol. 121, No. 4, pp (1999). 14. Hung, J. P., Lai, Y. L., Lin, C. Y., and Luo, T. L., Modeling the Machining Stability of a Vertical Milling Machine Under the Influence of the Preloaded Linear Guide, International Journal of Machine Tools and Manufacture, Vol. 51, No. 9, pp (2011). 15. Hung, J. P., Lai, Y. L., Luo, T. L., and Su, H. C., Analysis of the Machining Stability of a Milling Machine Considering the Effect of Machine Frame Structure and Spindle Bearings: Experimental and Finite Element Approaches, International Journal of Advanced Manufacturing Technology, Vol. 68, No. 9-12, pp (2013). 16. Mohit, L., Position-Dependent Dynamics and Stability of Machine Tools, Ph. D. Dissertation, Department of Mechanical Engineering, University of British Columbia, Vancouver, Canada (2013)

/MPa / kg m - 3 /MPa /MPa 2. 1E ~ 56 ANSYS 6 Hz (a) 一阶垂向弯曲 (b) 一阶侧向弯曲 (c) 一阶扭转 (d) 二阶侧向弯曲 (e) 二阶垂向弯曲 (f) 弯扭组合 2 6 Hz

/MPa / kg m - 3 /MPa /MPa 2. 1E ~ 56 ANSYS 6 Hz (a) 一阶垂向弯曲 (b) 一阶侧向弯曲 (c) 一阶扭转 (d) 二阶侧向弯曲 (e) 二阶垂向弯曲 (f) 弯扭组合 2 6 Hz 31 3 Vol. 31 No. 3 218 9 Journal of Shijiazhuang Tiedao University Natural Science Edition Sep. 218 1 1 2 1 2 1 1. 543 2. 543 U462. 3 217-2 - 16 A 295-373 218 3-63 - 6 1-4 5-7 8-11 1 11 11 398 mm 86 mm