In wire electrical discharge machining (WEDM) that can perform 2-D or 2.5-D machining, 3-D complex shape machining is also possible via the addition of a rotary axis on the NC table. Several examples of pin-shaped machining using a rotating shaft like spindle have been previously reported. Alternatively, machining using a rotary axis as an indexing device has also been reported. In these machining processes, the rotary axis is not servo controlled. Conversely, a spiral groove is formed on the outer circumference of the round bar by gripping the round bar workpiece on the rotary axis and performing machining in synchronization with the x- and rotary axes. In this machining, the gap control in electrical discharge machining is performed along the x- and rotary axes. Furthermore, complicated shape machining becomes possible by adding a 2-axis rotary axis of rotation and tilt. When the x-axis is synchronized with the rotation and tilt axes, a spiral groove with a variable groove width is formed. In this case, servo control is synchronized with the three axes, and machining proceeds. In this study, we performed spiral groove shape machining through WEDM with the addition of 1-axis or 2-axis rotary axes, consequently verifying the machining accuracy. Moreover, two types of NC program were used for machining, direct input and CAM output, and the accuracy was compared. The results revealed that the groove width was wider in the direct input program. Therefore, there was a possibility that the wire could bend during machining and tilt along the direction of the apparent widening of the groove width. Thus, it is necessary to consider the deflection of the wire in WEDM with a rotary axis, which is different from the conventional one, to realize precision machining.

1. [1] N. Kinoshita, M. Fukui, and Y. Kimura, “Study on Wire-EDM: Inprocess Measurement of Mechanical Behaviour of Electrode-Wire,” CIRP Annals – Manufacturing Technology, Vol.33, No.1, pp. 89-92, doi: 10.1016/S0007-8506(07)61386-9, 1984.
2. [2] Y. H. Huang, G. G. Zhao, Z. R. Zhang, C. Y. Yu, and Y. Z. Zhang, “The Identification and Its Means of Servo Feed Adaptive Control System in WEDM,” CIRP Annals – Manufacturing Technology, Vol.35, No.1, pp. 121-123, doi: 10.1016/S0007-8506(07)61852-6, 1986.
3. [3] K. P. Rajurkar, W. M. Wang, and R. P. Lindsay, “On-Line Monitor and Control for Wire Breakage in WEDM,” CIRP Annals – Manufacturing Technology, Vol.40, No.1, pp. 219-222, doi: 10.1016/S0007-8506(07)61972-6, 1991.
4. [4] N. Mohri, H. Yamada, K. Furutani, T. Narikiyo, and T. Magara, “System identification of wire electrical discharge machining,” CIRP Annals – Manufacturing Technology, Vol.47, No.1, pp. 173-176, doi: 10.1016/s0007-8506(07)62811-x, 1998.
5. [5] M. Kunieda and C. Furudate, “High precision finish cutting by dry WEDM,” CIRP Annals – Manufacturing Technology, Vol.50, No.1, pp. 121-124, doi: 10.1016/S0007-8506(07)62085-X, 2001.
6. [6] G. Kappmeyer, C. Hubig, M. Hardy, M. Witty, and M. Busch, “Modern Machining of Advanced Aerospace Alloys – Enabler for Quality and Performance,” Procedia CIRP, Vol.1, pp. 28-43, doi: 10.1016/j.procir.2012.04.005, 2012.
7. [7] S. Jeelani and M. Collins, “Effect of Electric Discharge Machining on the Fatigue Life of Inconel 718,” Int. J. of Fatigue, Vol.10, No.2, pp. 121-125, doi: 10.1016/j.procir.2012.04.005, 1988.
8. [8] Y. S. Liao and Y. P. Yu, “The Energy Aspect of Material Property in WEDM and Its Application,” J. of Materials Processing Technology, Vol.149, Nos.1-3, pp. 77-82, doi: 10.1016/j.jmatprotec.2003.10.031, 2004.
9. [9] L. Li, Y. B. Guo, X. T. Wei, and W. Li, “Surface Integrity Characteristics in Wire-EDM of Inconel 718 at Different Discharge Energy,” Procedia CIRP, Vol.6, pp. 220-225, doi: 10.1016/j.procir.2013.03.046, 2013.
10. [10] M. J. Haddad and A. F. Tehrani, “Material removal rate (MRR) study in the cylindrical wire electrical discharge turning (CWEDT) process,” J. of Materials Processing Technology, Vol.199, pp. 369-378, doi: 10.1016/j.jmatprotec.2007.08.020, 2008.
11. [11] Y. Zhu, T. Liang, L. Gu, and W. Zhao, “Machining of Micro Rotational Parts with Wire EDM Machine,” Procedia Manufacturing, Vol.5, pp. 849-856, doi: 10.1016/j.promfg.2016.08.071, 2016.
12. [12] A. Mohammadi, A. F. Tehrani, and A. Abdullah, “Introducing a new technique in wire electrical discharge turning and evaluating ultrasonic vibration on material removal rate,” Procedia CIRP, Vol.6, pp. 583-588, doi: 10.1016/j.procir.2013.03.005, 2013.
13. [13] T. Bergs, U. Tombul, D. Mevissen, A. Klink, and J. Brimmers, “Load Capacity of Rolling Contacts Manufactured by Wire EDM Turning,” Procedia CIRP, Vol.87, pp. 474-479, doi: 10.1016/j.procir.2020.02.111, 2020.
14. [14] A. Owhal, N. Srinivasa Rao, U. Gupta, and M. Mahajan, “Extension of Wire-EDM Capability for Turning Titanium Alloy and an Experimental Study for Process Optimization by Grey Relational Analysis,” Materials Today: Proc., Vol.24, pp. 966-974, doi: 10.1016/j.matpr.2020.04.409, 2020.
15. [15] T. Masuzawa, M. Fujino, K. Kobayashi, T. Suzuki, and N. Kinoshita, “Wire Electro-Discharge Grinding for Micro-Machining,” CIRP Annals – Manufacturing Technology, Vol.34, No.1, pp. 431-434, doi: 10.1016/S0007-8506(07)61805-8, 1985.
16. [16] T. Bergs, U. Tombul, T. Herrig, A. Klink, and D. Welling, “Influence of an Additional Indexing Rotary Axis on Wire Electrical Discharge Machining Performance for the Automated Manufacture of Fir Tree Slots,” J. of Engineering for Gas Turbines and Power, Vol.142, No.9, 091005, doi: 10.1115/1.404680, 2020.
17. [17] D. F. Dauw, H. Sthioul, R. Delpretti, and C. Tricarico, “Wire Analysis and Control for Precision EDM Cutting,” CIRP Annals – Manufacturing Technology, Vol.38, No.1, pp. 191-194, doi: 10.1016/S0007-8506(07)62682-1, 1989.
18. [18] A. Okada, Y. Uno, M. Nakazawa, and T. Yamauchi, “Evaluations of Spark Distribution and Wire Vibration in Wire EDM by High-Speed Observation,” CIRP Annals – Manufacturing Technology, Vol.59, No.1, pp. 231-234, doi: 10.1016/j.cirp.2010.03.073, 2010.
19. [19] A. Okada, T. Konishi, Y. Okamoto, and H. Kurihara, “Wire Breakage and Deflection Caused by Nozzle Jet Flushing in Wire EDM,” CIRP Annals – Manufacturing Technology, Vol.64, No.1, pp. 233-236, doi: 10.1016/j.cirp.2015.04.034, 2015.
20. [20] A. Condea, J. A. Sanchez, S. Plaza, and J. M. Ramos, “On the influence of wire-lag on the WEDM of low-radius free-form geometries,” Procedia CIRP, Vol.42, pp. 274-279, doi: 10.1016/j.procir.2016.02.285, 2016.