A new technique for identification and evaluation of wear in copper electrodes in electrical discharge machining using acoustic emission signals

Author(s):  
Samuel Soares Ferreira ◽  
Fred Lacerda Amorim ◽  
Jánes Landre Júnior ◽  
Luís Henrique Andrade Maia ◽  
Álisson Rocha Machado ◽  
...  
2009 ◽  
Vol 626-627 ◽  
pp. 321-326
Author(s):  
Bao Xian Jia ◽  
D.S. Wang ◽  
Jing Zhe Guo

In order to obtain micro holes with high aspect ratio, a new technique of machining deep micro holes by combining EDM (Electrical Discharge Machining) with USM (Ultrasonic Machining) in inversion installing is researched. The workpiece is over the electrode. The ultrasonic vibration is affixed to the electrode. The workpiece and electrode are all immersed in working liquid. The debris generated by EDM is dropped out the hole from the gap between the electrode and the hole wall by the gravity and the pumping effect of ultrasonic vibration, so as to increasing the machining velocity and machined depth. The structural features of the machining device are described, and the exploratory experiment is carried out. The corresponding process relations are found out, which can provide references for further study of this technique. The micro holes with larger than 25 in aspect ratio are machined.


2008 ◽  
Vol 33-37 ◽  
pp. 1181-1186 ◽  
Author(s):  
M. Mahardika ◽  
Kimiyuki Mitsui ◽  
Zahari Taha

The mechanism of fracture in micro-electrical discharge machining (-EDM) processes is related to the discharge pulses energy. This paper investigates the correlation of fractures and discharge pulses energy in the -EDM of polycrystalline diamond (PCD) to the acoustic emission (AE) signals. The evaluation of fracture mechanism was done by measuring the generation and propagation of elastic wave in single discharge pulse by using AE sensor. The results show a strong correlation between fractures and discharge pulses energy to the AE signals and mechanism of material removal in the -EDM processes.


Author(s):  
Kanka Goswami ◽  
GL Samuel

Micro-electrical discharge machining is a stochastic process where the interaction between the materials and the process parameters are difficult to understand. Monitoring of the process becomes necessary to achieve the dimensional accuracy of the micro-featured components. Although thermo-mechanical erosion is the most accepted material-removal mechanism, it fails to explain the material removal with very short pulse duration. Alternative postulate like electrostatic force-induced stress yielding provides a stronger argument, rising ambiguity over the material-removal process in the micro-electrical discharge machining regime. In this work, it was found that the stress waves released from the material during micro-electrical discharge-machining process indicate material removal by mechanical deformation and fracture mechanism. These stress waves were captured using the acoustic emission sensor. The discharge pulses were captured by voltage measurement and classified using voltage gradient and machining time duration into three major categories, open pulse, normal pulse and arc pulse. The acoustic emission signal features were extracted and identified by time–frequency–energy distribution analysis. A feed-forward back-propagation neural network mapping of the pulse instances was performed with the obtained acoustic emission signature. The time–frequency–energy distribution analysis of the acoustic emission and the scanning electron microscope images of the craters provide conclusive evidence that the material is removed by mechanical stress and fracture. The feed-forward back-propagation network model was trained to predict the discharge categories of the pulse instances with AE signal inputs which can be used for monitoring the material-removal mechanism in micro-electrical discharge machining operation.


Author(s):  
Raja Das ◽  
M. K. Pradhan

The objective of the chapter is to present the application of Artificial Neural Network (ANN) modelling of the Electrical Discharge Machining (EDM) process. It establishes the best ANN model by comparing the prediction from different models under the effect of process parameters. In EDM, the motivation is frequently to get better Material Removal Rate (MRR) with fulfilling better surface quality of machined components. The vital requirements are as small a radial overcut with minimal tool wear rate. The quality of a machined surface is very important to fulfilling the growing demands of higher component performance, durability, and reliability. To improve the reliability of the machine component, it is necessary to have in depth knowledge of the effect of parameters on the aforesaid responses of the components. An extensive chain of experiments has been conducted over a wide range of input parameters, using the full factorial design. More than 150 experiments have been conducted on AISI D2 work piece materials using copper electrodes to get the data for training and testing. The additional experiments were obtained to validate the model predictions. The performance of three neural network models is discussed in the evaluation of the generalization ability of the trained neural network. It was observed that the artificial neural network models could predict the process performance with reasonable accuracy, under varying machining conditions.


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