Multi-objective optimisation of high-speed electrical discharge machining process using a Taguchi fuzzy-based approach

(BQ) The paper describes the application of the fuzzy logic analysis coupled with Taguchi methods to optimise the precision and accuracy of the high-speed electrical discharge machining (EDM) process. A fuzzy logic system is used to investigate relationships between the machining precision and accuracy for determining the efficiency of each parameter design of the Taguchi dynamic experiments.
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Multi-objective optimisation of high-speed electrical discharge machining process using a Taguchi fuzzy-based approachMaterials& DesignMaterials and Design 28 (2007) 1159–1168www.elsevier.com/locate/matdesMulti-objective optimisation of high-speed electricaldischarge machining process using a Taguchi fuzzy-based approachYih-fong Tzengaa,*, Fu-chen ChenbDepartment of Mechanical and Automation Engineering, National Kaohsiung First University of Science and Technology, No. 1 University Road,Yen-Chao, Kao-Hsiung 824, TaiwanbDepartment of Mechanical Engineering, Kun Shan University, No. 949 Da Wan Rd., Yung-Kang, Tainan Hsien 710, TaiwanReceived 9 August 2005; accepted 19 January 2006Available online 3 April 2006tool steel SKD11AbstractThe paper describes the application of the fuzzy logic analysis coupled with Taguchi methods to optimise the precision and accuracyof the high-speed electrical discharge machining (EDM) process. A fuzzy logic system is used to investigate relationships between themachining precision and accuracy for determining the efficiency of each parameter design of the Taguchi dynamic experiments. Fromthe fuzzy inference process, the optimal process conditions for the high-speed EDM process can be easily determined asA1B1C3D1E3F3G1H3. In addition, the analysis of variance (ANOVA) is also employed to identify factor B (pulse time), C (duty cycle),and D (peak value of discharge current) as the most important parameters, which account for about 81.5% of the variance. The factors E(powder concentration) and H (powder size) are found to have relatively weaker impacts on the process design of the high-speed EDM.Furthermore, a confirmation experiment of the optimal process shows that the targeted multiple performance characteristics are significantly improved to achieve more desirable levels.Ó 2006 Elsevier Ltd. All rights reserved.Keywords: Electrical discharge machining (EDM); Fuzzy logic analysis; Analysis of variance (ANOVA); Machining precision and accuracy1. IntroductionElectrical discharge machining (EDM) is a thermal process with a complex metal-removal mechanism, involvingthe formation of a plasma channel between the tool andworkpiece. It has proved especially valuable in the machining of super-tough, electrically conductive materials such asthe new space-age alloys that are difficult to machine byconventional methods [1]. For several decades, EDM hasbeen an important manufacturing process for the mouldand die industry. Although the EDM process is not affectedby material hardness and strength, it is much slower compared to the milling and turning processes. To speed up theprocess, large electrical current discharge is usuallyrequired, but concurrently the dimensional quality of the*Corresponding author. Tel.: +886 7 6011006; fax: +886 7 6011066.E-mail address: franktzeng@ccms.nkfuse.edu.tw (Y.-f. Tzeng).0261-3069/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.doi:10.1016/j.matdes.2006.01.028machined product inevitably became worse. On the otherhand, it is well known that EDM process is very unstableowing to arcing when too much debris exists inside thegap. Therefore, how to develop an EDM process with thecapability of high machining rate, and high precision andaccuracy without major alterations to the EDM systemremains a big challenge.To improve the EDM technology, many efforts havebeen directed to enhance the process stability. Introducingforeign particles into the working fluid was one of the useful approaches to improve the EDM performance. Example applications include the surface modification methodby EDM with a green compact electrode and powder suspended in working fluid by Furutani et al. [2]; near-mirror-finish EDM technology using powder-mixed dielectricby Wong et al. [3]; the effects of powder characteristicson precision and rough electrical discharge machining efficiency by Tzeng et al. [4–6]. The other approaches include1160Y.-f. Tzeng, F.-c. Chen / Materials and Design 28 (2007) 1159–1168the use of ultrasonic vibration to assist EDM process forimproving the material removal rate by Zhang et al. [7,8];the effects of various process parameters on EDM byHocheng et al. [9].Traditionally, the operating parameters of the EDMprocess are mainly set based on the trial and error experience of the operator or the information provided by thetool suppliers. This method is neither cost-efficient nor useful for quality control. Taguchi proposes a procedure thatapplies orthogonal arrays from statistical design of experiments to efficiently obtain the best model with the leastnumber of experiments [10]. However, most previous applications of the Taguchi methods emphasize only on singlequality characteristic and, in comparison, paid little attention on multiple performance characteristics (MPCs) [11–15]. Nevertheless, the MPCs of a product are still generallyrequired by the c ...