CONDITIONS FOR STABLE CHIP BREAKING AND PROVISION OF MACHINED SURFACE QUALITY WHILE TURNING WITH ASYMMETRIC TOOL VIBRATIONS

The paper considers a process of turning structural steel with asymmetric tool vibrations directed along feeding. Asymmetric vibrations characterized by asymmetry coefficient of vibration cycle, their frequency and amplitude are additionally transferred to the tool in the turning process with the purpose to crush chips. Conditions of stable chip breaking and obtaining optimum dimensions of chip elements have been determined in the paper. In order to reduce a negative impact of the vibration amplitude on a cutting process and quality of the machined surfaces machining must be carried out with its minimum value. In this case certain ratio of the tool vibration frequency to the work-piece rotation speed has been ensured in the paper. A formula has been obtained for calculation of this ratio with due account of the expected length of chip elements and coefficient of vibration cycle asymmetry.

Influence of the asymmetric coefficient of the tool vibration cycle on roughness of the machined surfaces and cutting tool wear has been determined in the paper. According to the results pertaining to machining of work-pieces made of 45 and ШХ15 steel the paper presents mathematical relationships of machined surface roughness with cutting modes and asymmetry coefficient of tool vibration cycle. Tool feeding being one of the cutting modes exerts the most significant impact on the roughness value and increase of the tool feeding entails increase in roughness. Reduction in coefficient of vibration cycle asymmetry contributes to surface roughness reduction. However, the cutting tool wear occurs more intensive. Coefficient of the vibration cycle asymmetry must be increased in order to reduce wear rate. Therefore, the choice of the coefficient of the vibration cycle asymmetry is based on the parameters of surface roughness which must be obtained after machining and intensity of tool wear rate.

The paper considers a process of turning structural steel with asymmetric tool vibrations directed along feeding. Asymmetric vibrations characterized by asymmetry coefficient of vibration cycle, their frequency and amplitude are additionally transferred to the tool in the turning process with the purpose to crush chips. Conditions of stable chip breaking and obtaining optimum dimensions of chip elements have been determined in the paper. In order to reduce a negative impact of the vibration amplitude on a cutting process and quality of the machined surfaces machining must be carried out with its minimum value. In this case certain ratio of the tool vibration frequency to the work-piece rotation speed has been ensured in the paper. A formula has been obtained for calculation of this ratio with due account of the expected length of chip elements and coefficient of vibration cycle asymmetry.

Influence of the asymmetric coefficient of the tool vibration cycle on roughness of the machined surfaces and cutting tool wear has been determined in the paper. According to the results pertaining to machining of work-pieces made of 45 and ШХ15 steel the paper presents mathematical relationships of machined surface roughness with cutting modes and asymmetry coefficient of tool vibration cycle. Tool feeding being one of the cutting modes exerts the most significant impact on the roughness value and increase of the tool feeding entails increase in roughness. Reduction in coefficient of vibration cycle asymmetry contributes to surface roughness reduction. However, the cutting tool wear occurs more intensive. Coefficient of the vibration cycle asymmetry must be increased in order to reduce wear rate. Therefore, the choice of the coefficient of the vibration cycle asymmetry is based on the parameters of surface roughness which must be obtained after machining and intensity of tool wear rate.

1. Akhmetshin, N. I., Gots, E. M., Rodikov, N. F., Ragulskis, K. M. (1987) Vibratory Cutting of Metals. Leningrad, Mashinostroenie, Leningrad Branch. 80 p. (in Russian).

2. Ilyin, V. S., Kondratov, A. S., Bubnov, B. N. (1975) Methods for Curling and Breaking Chips While Using Software-Controlled Turning Machines: Technological Recommendations. Moscow: Scientific-Research Institute of Technology and Production Engineering (NIAT). 24 p. (in Russian).

3. Zakharov, Yu. E., Garbuziuk, V. T. (1970) Useful Vibrations in Mechanical Engineering. Tula, Priokskoe Publishing House. 112 p. (in Russian).

4. Methods for Curling and Breaking Flow Chips and Fields of Their Application. Instructive Materials (1970). Moscow, All-Union Scientific-Research Institute of Information on Mechanical Engineering. 38 p. (in Russian).

5. Mansyrev, I. G., Smirnov, A. A., Kozar, I. I. (1983) Methods for Crushing Flow Chips During Cutting Process. Leningrad, Leningrad House of Scientific-Research Promotion [LDNTP]. 20 p. (in Russian).

6. Bogoslovsky, N. V., Ivashchenko, T. I. (1991) Kinematic Chip Breaking While Turning Hard-To-Machine Steel. Zubarev, Yu. M. (ed.). Ways to Improve Efficiency of Material Machining While Using Cutting in Mechanical Enginering. Proceedings of Short-Term Scientific and Technical on May 13–14. Leningrad, Znanie, 47–48 (in Russian).

7. Konovalov, E. G., Borisenko, A. V. (1960) Oscillating Turning. Minsk: Publishing House of the Academy of Sciences of the Belorussian SSR. 32 p. (in Russian).

8. Poduraev, V. N. (1970) Cutting with Vibrations. Moscow, Mashinostroenie. 350 p. (in Russian).

9. Danilchyk, S. S., Sheleg, V. K. (2013) Turning Kinematics with Imposition of Asymmetric Tool Vibrations. Nauka i Tekhnika [Science and Technique], 4, 16–21 (in Russian).

10. Vulf, ?. ?. (1973) Metal Cutting. 2nd Edition. Leningrad, Mashinostroenie. 496 p. (in Russian).

11. Katsev, P. G. (1968) Statistical Methods for Investigation Cutting Tool. Moscow, Mashinostroenie. 156 p. (in Russian).

12. Makarov, ?. D., Mukhin, V. S., Shuster, L. Sh. (1974) Tool Wear, Quality and Durability of Parts Made of Aircraft Materials. Ufa: Ufa Aviation Institute. 372 p. (in Russian).