Statistical analysis on electrode wear in EDM of tool steel DIN 1.2714 used in forging dies

doi:10.1016/j.jmatprotec.2006.11.202

Journal of Materials Processing Technology

Volumes 187–188, 12 June 2007, Pages 711-714

https://doi.org/10.1016/j.jmatprotec.2006.11.202 Get rights and content

Abstract

Electrical discharge machining (EDM) is a widespread process which works very effectively in machining of difficult-to-cut materials and alloys in die and aerospace industries with high dimensional accuracies. However, this capability could be deteriorated due to electrode wear leading to decrease of process productivity. In this study, the effect of machining parameters of EDM process including on-time, current, voltage, the engaging time between workpiece and electrode, and pre-EDM roughing on electrode wear were experimentally investigated. Main effects of factors and interactions were considered in this paper and regression equation was derived. A L₅₀ (2¹ × 5¹¹) Taguchi's standard orthogonal array was employed as experimental design. Copper was used as electrode to machine the hot work tool steel 1.2714, which is widely used to make forging dies and mandrels.

Introduction

Among the non-traditional methods of material removal processes, electrical discharge machining (EDM) has drawn a great a deal of researchers’ attention because of its broad industrial applications. This process is well suited for machining of casting and forging dies, powder metallurgy and injection molds, and aerospace parts.

The process is a spark erosion method, eroding the workpiece by high frequency spark discharges [1]. EDM has a high capability of machining the accurate cavities of dies and molds. Nevertheless, electrode wear occurs during EDM process leading to a lack of machining accuracy in the geometry of workpiece [2]. Furthermore, electrode wear imposes high costs on manufacturers to substitute the eroded complicated electrodes by new ones for die making. In order to increase the machining efficiency, erosion of the workpiece must be maximized and that of the electrode minimized in EDM process [1]. Therefore, studying the electrode wear and related significant factors would be effective to enhance the machining productivity and process reliability.

A series of investigations have been conducted on electrode wear in EDM process. Soni and Chakraverti [3], [4] studied the surface quality, material removal rate, wear ratio, and dimensional accuracy in EDM of alloy steels. Singh et al. investigated the effect of machining parameters on electrode wear in die-sinking EDM of En-31 tool steel with different electrode materials [5]. Also, Luis et al. have carried out a study on electrode wear in EDM of silicon carbide using the technique of design of experiments [6].

In this research, an experimental study is conducted to investigate on electrode wear in die-sinking EDM of DIN 1.2714 hot work tool steel. The selection of this material was made taking into account its wide range of applications in die and mold industries such as hammer and hydraulic forging dies. The aim of this study is to find out from which process parameters (factors) electrode wear is affected and to which factor interactions it is related. This is usually done by means of analysis of variance (ANOVA). Furthermore, regression analysis is used to establish the correlation between factors and response (tool wear). The appropriate degree of the polynomial regression equation is found which is thought to be useful assessment of the predictive equation [7], [8]. Finally, the optimal factor levels are obtained.

Section snippets

Experimental design

During EDM experiments, the input parameters (factors) were on-time (pulse-on duration), peak current, pulsed voltage, engaging time, and pre-EDM roughing accuracy. The pulse-off duration was kept constant which could effectively control the flushing of the debris from the gap, giving machining stability. Therefore, the effect of the pulse-off duration on machining process was not considered in the present work. Table 1 shows factors and factor levels assessed in this study.

The design of

Effect of factors and interactions on electrode wear

Fig. 2 depicts the plot of main effects for electrode wear. Note that this plot illustrates data means versus factor levels. Based on this plot, the effect of each factor can be graphically assessed.

Fig. 2a shows that pre-EDM roughing factor has a significant effect on electrode wear. It can also be seen from this figure that the effect of this factor is directly proportional to electrode wear. Also, it can be stated that by increasing the pre-EDM roughing factor electrode wear increases

Conclusions

In this research, an experimental investigation was performed to consider the electrode wear in EDM process of DIN 1.2714 tool steel and the following results were concluded:

1.
On-time, current, and pre-EDM roughing as factors along with on-time/current, on-time/pre-EDM roughing, and current/pre-EDM roughing as interactions, were found to have significant effect on electrode wear.
2.
The predictive model was derived out of regression analysis.
3.
The adequacy of predictive model was approved.
4.
Optimal level

Acknowledgements

The authors appreciate Abzaran Co. and Industrial Cooperation Office of Isfahan University of Technology for supporting this research. Also, a special thanks to M. Pourehsan and M. Neshatpour for their close cooperation.

References (9)

C.C. Liu
Microstructure and tool electrode erosion in EDM of TiN/Si₃N₄ composites
Mater. Sci. Eng. J.
(2003)
Y.Y. Tsai et al.
An index to evaluate the wear resistance of the electrode in micro-EDM
J. Mater. Process. Technol.
(2004)
S. Singh et al.
Some investigations into the electric discharge machining of hardened tool steel using different electrode materials
J. Mater. Process. Technol.
(2004)
C.J. Luis et al.
Material removal rate and electrode wear study on the EDM of silicon carbide
J. Mater. Process. Technol.
(2005)

There are more references available in the full text version of this article.

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Statistical analysis on electrode wear in EDM of tool steel DIN 1.2714 used in forging dies

Abstract

Introduction

Section snippets

Experimental design

Effect of factors and interactions on electrode wear

Conclusions

Acknowledgements

Mater. Sci. Eng. J.

J. Mater. Process. Technol.

J. Mater. Process. Technol.

J. Mater. Process. Technol.