Research on feed-pulse collaborative control method in micro-electrical discharge machining

Abstract

Reducing the short-circuit rate and increasing the effective discharge rate are important targets for improving the servo control effect of micro-electrical discharge machining (micro-EDM), as these two indicators are closely related to the machining efficiency and quality. In this study, a feed-pulse collaborative control (FPCC) method is proposed for micro-EDM based on two dimensions (space and time). In the spatial dimension, a feed control strategy with a discharge holding process is adopted. Meanwhile, in the time dimension, a forward-looking pulse control strategy is adopted, in which the pulse interval is adjusted based on a sequence analysis of feed commands and discharge states. Process experiments are carried out to determine the key parameters used in this method, including the discharge holding threshold and pulse interval adjustment value ($T_{{\text{off}_{{\text{adj}}} }}$). The feed smoothness and discharge sufficiency analyses of the experimental results show that compared to the traditional double threshold average voltage method, the FPCC method reduces the number of long-distance retreats by 64% and improves the effective discharge time by 40%.

Keywords

Micro-electrical discharge machining (micro-EDM) / Electrode feed control / Discharge pulse control / Machining surface quality

References

[1] Tong H, Wang Y, Li Y. Vibration-assisted servo scanning 3D micro EDM. J Micromech Microeng, 2008, 18(2): .

[2] Hashim NLS, Yahya A, Daud MR, et al. A review on electrical discharge machining servomechanism system. Sci Iran, 2015, 22(5): 1813-1832.

[3] Burek J, Babiarz R, Buk J, et al. The accuracy of finishing WEDM of inconel 718 turbine disc fir tree slots. Materials, 2021, 14(3): 562.

[4] Huang RN, Lou YJ, Chi GX (2010) Research on servo feeding system of micro WEDM. In: 2010 international conference on digital manufacturing and automation. IEEE, Changcha, 2010

[5] Tong H, Liu X, Pu Y, et al. Servo control optimization of micro discharge gap and its reasonable matching with scanning speed in servo scanning 3D micro EDM based on threshold control method. Int J Adv Manuf Technol, 2019, 105: 3057-3066.

[6] Almeida S, Mo J, Bil C, et al. Comprehensive servo control strategies for flexible and high-efficient wire electric discharge machining. A systematic review. Precis Eng, 2021, 71: 7-28.

[7] Zhou M, Mu X, He L, et al. Improving EDM performance by adapting gap servo-voltage to machining state. J Manuf Process, 2019, 37: 101-113.

[8] Zhou M, Wu J, Xu X, et al. Significant improvements of electrical discharge machining performance by step-by-step updated adaptive control laws. Mech Syst Signal Process, 2018, 101: 480-497.

[9] Zhang L, Jia Z, Liu W, et al. A two-stage servo feed controller of micro-EDM based on interval type-2 fuzzy logic. Int J Adv Manuf Technol, 2012, 59: 633-645.

[10] Jahan MP, Wong YS, Rahman M. A study on the quality micro-hole machining of tungsten carbide by micro-EDM process using transistor and RC-type pulse generator. J Mater Process Technol, 2009, 209(4): 1706-1716.

[11] Azhar WABW, Saleh T (2019) Development and performance evaluation of modular RC-based power supply for micro-EDM. In: 2019 7th international conference on mechatronics engineering (ICOM), IEEE, Putrajaya, 2019

[12] Jahan MP, Wong YS, Rahman M. A comparative study of transistor and RC pulse generators for micro-EDM of tungsten carbide. Int J Precis Eng Manuf, 2008, 9(4): 3-10.

[13] Hu MH, Li Y, Tong H (2010) Design and experimental study of a multi-mode controllable RC pulse generator for micro-EDM. In: international conference on advanced technology of design and manufacture (ATDM 2010), IET, Beijing, 2010

[14] Abhilash PM, Chakradhar D. Failure detection and control for wire EDM process using multiple sensors. CIRP J Manuf Sci Technol, 2021, 33: 315-326.

[15] Yan MT, Chien HT. Monitoring and control of the micro wire-EDM process. Int J Mach Tools Manuf, 2007, 47(1): 148-157.

[16] Kumar D, Singh NK, Bajpai V. Recent trends, opportunities and other aspects of micro-EDM for advanced manufacturing: a comprehensive review. J Braz Soc Mech Sci, 2020, 42(5): 222.

[17] Han F, Wachi S, Kunieda M. Improvement of machining characteristics of micro-EDM using transistor type isopulse generator and servo feed control. Precis Eng, 2004, 28(4): 378-385.

[18] Fu X, Zhang Q, Gao L, et al. A novel micro-EDM—piezoelectric self-adaptive micro-EDM. Int J Adv Manuf Technol, 2016, 85: 817-824.

[19] Lee WM, Liao YS. Adaptive control of the WEDM process using a self-tuning fuzzy logic algorithm with grey prediction. Int J Adv Manuf Technol, 2007, 34: 527-537.

[20] Zhang Z, Ming W, Zhang G, et al. A new method for on-line monitoring discharge pulse in WEDM-MS process. Int J Adv Manuf Technol, 2015, 81(5): 1403-1418.

[21] Yeo SH, Aligiri E, Tan PC, et al. A new pulse discriminating system for micro-EDM. Mater Manuf Process, 2009, 24(12): 1297-1305.

[22] Liao YS, Woo JC. The effects of machining settings on the behavior of pulse trains in the WEDM process. J Mater Process Technol, 1997, 71(3): 433-439.

[23] Muthuramalingam T, Mohan B, Rajadurai A, et al. Experimental investigation of iso energy pulse generator on performance measures in EDM. Mater Manuf Process, 2013, 28(10): 1137-1142.

[24] Tong H, Li Y, Wang Y, et al. Servo scanning 3D micro-EDM based on macro/micro-dual-feed spindle. Int J Mach Tools Manuf, 2008, 48(7/8): 858-869.

[25] Lim HS, Wong YS, Rahman M, et al. A study on the machining of high-aspect ratio micro-structures using micro-EDM. J Mater Process Technol, 2003, 140(1/3): 318-325.

Funding

National Natural Science Foundation of China http://dx.doi.org/10.13039/501100001809(52175426)

National Science and Technology Major Project http://dx.doi.org/10.13039/501100018537(2018ZX04005001)