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Frontiers of Mechanical Engineering

Front Mech Eng    2011, Vol. 6 Issue (4) : 419-428     https://doi.org/10.1007/s11465-011-0246-7
RESEARCH ARTICLE |
Ultrasonic assisted EDM: Effect of the workpiece vibration in the machining characteristics of FW4 Welded Metal
Mohammadreza SHABGARD(), Hamed KAKOLVAND, Mirsadegh SEYEDZAVVAR, Ramin Mohammadpour SHOTORBANI
Department of mechanical Engineering, University of Tabriz, Tabriz, Iran
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Abstract

This paper presents the results of experimental studies carried out to conduct a comprehensive investigation on the influence of ultrasonic vibration of workpiece on the characteristics of Electrical Discharge Machining (EDM) process of FW4 Welding Metal in comparison with the conventional EDM process. The studied process characteristics included the material removal rate (MRR), tool wear ratio (TWR), and surface roughness (Ra and Rmax) of the workpiece after the EDM and ultrasonic assisted EDM (US-EDM) processes. The experiments performed under the designed full factorial procedure and the considered EDM input parameters included pulse on-time and pulse current. The experimental results show that in short pulse on-times, material removal rate in the US-EDM process is approximately quadruple than that of the EDM process. On the contrary, in the long pulse on-times, ultrasonic vibration of work??piece leads to the reduction in the MRR. On the other hand, in short pulse on-times, the TWR in the US-EDM process is lower than that of in the EDM process, and this condition reverses with increase in the pulse on-time. Furthermore, the surface roughness of the workpiece machined by EDM process is slightly lower than that of applied to the US-EDM process.

Keywords electrical discharge machining (EDM)      material removal rate (MRR)      tool wear ratio (TWR)      surface roughness     
Corresponding Authors: SHABGARD Mohammadreza,Email:mrshabgard@tabrizu.ac.ir   
Issue Date: 05 December 2011
 Cite this article:   
Ramin Mohammadpour SHOTORBANI,Mohammadreza SHABGARD,Hamed KAKOLVAND, et al. Ultrasonic assisted EDM: Effect of the workpiece vibration in the machining characteristics of FW4 Welded Metal[J]. Front Mech Eng, 2011, 6(4): 419-428.
 URL:  
http://journal.hep.com.cn/fme/EN/10.1007/s11465-011-0246-7
http://journal.hep.com.cn/fme/EN/Y2011/V6/I4/419
Fig.1  Schematic diagram of production route of molds made of weld metal. (a) Mill-removing of the insert’s place; (b) MIG-welding of the insert place; (c) grinding of the mold face; (d) ED machining of the mold
Fig.2  Schematic construction of the experiment
Fig.3  Ultrasonic head assembled to the EDM head
Typical properties of FW4 welded steel (work??piece)Typical average properties of graphite (tool)
Density/(kg·m-3)7.8×103Bulk density/( g·cm-3)1.78
Hardness/HRC45.5Porosity12%
Melting point/°C2670Grain size/μm20
UTS/(N·mm-2)1200Hardness/shore65
Elastic module/GPa210Ash valueMax 0.3%
Thermal conductivity/(W·m-1·K-1)27.2Specific resistance/(μΩ·cm)1650
Metal analysis of FW4
CMnSiSPNiCrCuMoNbVTi
0.16%1.04%0.38%0.009%0.0013%1.66%9.3%0.04%2.56%0.01%0.03%0.09%
Tab.1  Mechanical and physical properties of the work??piece and tool material
Experiment DescriptionVariable
Work??pieceFW4
ToolGraphite
Tool polarityPositive
Generator typeIso-pulse
DielectricOil flux ELF 2
Flashing typeNormal submerged
Discharge current/A4-8
Pulse on-time/μs6.4-12.8-25-50
Pulse off-time/μs6.4
Vibration frequency/kHz20
Vibration amplitude/μm15
Open voltage/V200
Tab.2  Experimental conditions
Fig.4  (a) Cylindrical rod cut with Wire-EDM; (b) final workpiece that has been Machined and screwed; (c) machined graphite tool machined
Fig.5  MRR vs. pulse on-time ( = 4 A)
Fig.6  MRR vs. pulse on-time ( = 8 A)
Fig.7  Effects of vibration on the plasma particles []
Fig.8  Typical records of the voltage and pulse current. (a) US-EDM process ( = 4 A and = 6.4 μs); (b) EDM process ( = 4 A and = 6.4 μs); (c) US-EDM process ( = 4 A and = 50 μs)
Fig.9  Typical pictures showing the presence of a black film on the surface of workpiece after the machining process. (a) EDM process ( = 4 A and = 6.4 μs); (b) US-EDM process ( = 4 A and = 6.4 μs); (c) EDM process ( = 4 A and = 50 μs); (d) US-EDM process ( = 4 A and = 50 μs)
Fig.10  TWR vs. pulse on-time ( = 4 A)
Fig.11  TWR vs. pulse on-time ( = 8 A)
Fig.12  TW vs. pulse on-time ( = 4 A)
Fig.13  TW vs. pulse on-time ( = 8 A)
Fig.14  Microscopic photograph of graphite surface before exposing to the ultrasonic vibration (without spark)
Fig.15  Microscopic photograph of graphite surface after exposing to the ultrasonic vibration (without spark)
Fig.16  vs. pulse on-time (= 4 A)
Fig.17  vs. pulse on-time ( = 8 A)
Fig.18  vs. pulse on-time ( = 4 A)
Fig.19  vs. pulse on-time (= 8 A)
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