A method to uniquely calculate the tool path and to modify the tool path during air cutting motion to reduce the machining time is proposed. This study presents a contour line model, in which the product model is minutely divided on a plane along an axial direction, and the contour line of the cross-section of the product is superimposed. A method is then proposed to calculate the tool position according to the degree of interference between the product surface and the tool. Furthermore, this study proposes a technique to reduce the machining time by tool path modification during air cutting motion. This is determined by the geometric relationship between the product surface and the tool, and not based on cutting simulations. A cutting experiment was conducted to validate the effectiveness of the proposed method. Based on the results, it was confirmed that the difference in machining time between the tool path with modification and the tool path without modification was large. Moreover, the machining time was significantly reduced by the tool path modification. The results showed that the proposed method has good potential to perform customized manufacturing, and to realize both high productivity and reliability in machining operation.

1. [1] K. Nakamoto, K. Shirase, H. Wakamatsu, A. Tsumaya, and E. Arai, “Development of Digital Copy Milling System to Realize NC Programless Machining: 3rd Report, Machining Strategy for In-Process Adaptation of Cutting Conditions,” Trans. of the Japan Society of Mechanical Engineers Series C, Vol.69, No.677, pp. 270-277, 2003.
2. [2] K. Shirase and K. Nakamoto, “Direct Machining Operation Performed by Autonomous NC Machine Tool Controlled by Digital Copy Milling Concept,” Trans. of the Japan Society of Mechanical Engineers Series C, Vol.74, No.743, pp. 1901-1906, 2008.
3. [3] K. Shirase and K. Nakamoto, “Simulation Technologies for the Development of an Autonomous and Intelligent machine Tool,” Int. J. Automation Technol., Vol.7, No.1, pp. 6-15, 2013.
4. [4] K. Shirase, T. Kondo, M. Okamoto, H. Wakamatsu, and E. Arai, “Development of Virtual Copy Milling System to Realize NC Programless Machining: Real Time Tool Path Generation for Autonomous NC Machine Tool,” The Japan Society of Mechanical Engineers, Vol.66, No.644, pp. 1368-1373, 2000.
5. [5] Y. Altintas and W. K. Munasinghe, “A Hierarchical Open-Architecture CNC System for Machine Tools,” CIRP Annals, Vol.43, No.1, pp. 349-354, 1994.
6. [6] M. Mitsuishi, T. Nagao, T. Ohta, and H. Okabe, “A Practical Machining Condition Determination Strategy Using Multi-Axis Force Information,” Annals of CIRP, Vol.45, No.1, pp. 373-376, 1996.
7. [7] M. Mitsuishi, T. Nagao, H. Okabe, and M. Katsuya, “An Open Architecture CNC CAD-CAM Machining System with Data-Base Sharing and Mutual Information Feedback,” Annals of CIRP, Vol.46, No.1, pp. 269-274, 1997.
8. [8] T. Hasegawa, R. Sato, and K. Shirase, “Cutting Force Simulation Referring Workpiece Voxel Model for End-milling Operation and Adaptive Control Based on Predicted Cutting Force,” J. of the Japan Society for Precision Engineering, Vol.82, No.5, pp. 467-472, 2016.
9. [9] I. Nishida, R. Tsuyama, R. Sato, and K. Shirase, “Customized End Milling Operation of Dental Artificial Crown without CAM Operation,” Int. J. Automation Technol., Vol.12, No.6, pp. 947-954, 2018.
10. [10] J. Tlusty and P. MacNeil, “Dynamics of Cutting Forces in End Milling,” CIRP Annals, Vol.24, No.1, pp. 21-25, 1975.
11. [11] D. Mongomery and Y. Altintas, “Mechanism of cutting force and surface generation in dynamic milling,” J. of Engineering for Industry, Vol.113, No.2, pp. 160-168, 1991.
12. [12] Y. Altintaş and P. Lee, “A General Mechanics and Dynamics Model for Helical End Mills,” CIRP Annals, Vol.45, No.1, pp. 59-64, 1996.
13. [13] K. Shirase and Y. Altintas, “Cutting force and dimensional surface error generation in peripheral milling with variable pitch helical end mills,” Int. J. of Machine Tools and Manufacture, Vol.36, No.5, pp. 567-584, 1996.
14. [14] T. Nishikawa, K. Kikuta, M. Mondou, T. Tsutsumoto, and J. Kaneko, “Machining Error Compensation System in End Milling,” J. of the Japan Society for Precision Engineering, Vol.78, No.11, pp. 975-979, 2012.
15. [15] Y. Takeuchi, M. Sakamoto, Y. Abe, R. Orita, and T. Sata, “Development of a personal CAD/CAM system for mold manufacture based on solid modeling techniques,” CIRP Annals, Vol.38, No.1, pp. 429-432, 1989.
16. [16] M. Inui, “Fast Simulation of Sculptured Surface Milling with 3-Axis NC Machine,” Trans. of Information Processing Society of Japan, Vol.40, No.4, pp. 1808-1815, 1999.
17. [17] T. Kishinami, S. Kanai, H. Shinjo, H. Nakahara, and K. Saito, “An application of voxel representation to machining simulator,” J. of the Japan Society for Precision Engineering, Vol.55, No.1, pp. 105-110, 1989.
18. [18] S. Hauth, Y. Murtezaoglu, and L. Linsen, “Extended linked voxel structure for point-to-mesh distance computation and its application to NC collision detection,” Computer-Aided Design, Vol.41, No.12, pp. 896-906, 2009.
19. [19] Y. Tsuchitana, J. Kaneko, and K. Horio, “Fast Simulation Algorithm of Voxel Representation Method for Multi Axis Control Machining,” J. of the Japan Society for Precision Engineering, Vol.79, No.5, pp. 467-472, 2013.
20. [20] I. Nishida, R. Sato, and K. Shirase, “High Speed Computational Algorithm in Voxel Based Milling Process Simulation for Minute Time and Minute Space Resolution Analysis,” J. of the Japan Society for Precision Engineering, Vol.84, No.2, pp. 175-181, 2018.
21. [21] I. Nishida, R. Okumura, R. Sato, and K. Shirase, “Cutting Force Simulation in Minute Time Resolution for Ball End Milling Under Various Tool Posture,” J. of Manufacturing Science and Engineering, Vol.140, No.2, 021009, doi: 10.115/1.4038499, 2017.
22. [22] I. Nishida, R. Okumura, R. Sato, and K. Shirase, “Voxel Based End-milling Simulation Considering Elastic Deflection of Tool System,” J. of the Japan Society for Precision Engineering, Vol.84, No.6, pp. 572-577, 2018.