H. Zarepour

A New Pulse Discriminating System for Micro-EDM

A new pulse discriminating technique for monitoring microelectrical discharge machining (micro-EDM) process in real time is proposed. The proposed system employs current pulse as the main detecting parameter as it is considered to be a better representation of the spark energy inside plasma channel as compared to the voltage. Micro-EDM pulses are classified into normal discharge, delayed discharge, arcing, and short circuit. The developed system was tested on micro-EDM drilling and micro-EDM milling, and the pulse distributions throughout these processes were analyzed. The developed pulse discriminator (PD) system is further used in the development of an adaptive speed servo system in micro-EDM. Experiment results show that the system is able to improve the machining time by more than 50%, and the accuracy of the resulting features is increased.

An Adaptive Speed Control System for Micro Electro Discharge Machining

The integration of the state‐of‐the‐art monitoring and adaptive control technologies can substantially improve the performance of EDM process. This paper reports the development of an adaptive speed control system for micro EDM which demands a higher level of accuracy. Monitoring of the machining state is conducted during the machining process so that the conditions are analysed continuously. Various schemes for the machining state are used for decision making. For instance, upon recognition of abnormal discharges, the developed adaptive speed control system would adjust the electrode feeding speed in an attempt to correct the machining state. Experimental verification shows that the proposed system can improve the machining time by more than 50%. In addition, a more accurate machined feature can be produced as compared to traditional EDM servo control systems.

Statistical Analysis of Hard Turning of AISI 4340 Steel on Surface Finish and Cutting Region Temperature

The focus of this study is to investigate the effects of cutting speed, feed rate, hardness and cutting tool material on cutting region temperature and surface finish in hard turning process. A L36 Taguchis standard orthogonal array was applied as experimental design. Machining tests were conducted under controlled conditions. AISI 4340 alloy steel which has numerous industrial applications was used to perform machining experiments. CBN, ceramic and cermet tools were employed to accomplish 36 tests with three random repetitions, resulting in 108 experiments. Main effects of the factors and their interactions are considered in this study using ANOVA (Analysis of variance) method. Also predictive models are derived by regression. Furthermore, optimal factor levels are obtained through S/N (signal to noise) ratio analysis in order to increase the machining efficiency. Finally, the results of confirmation tests are presented to verify the adequacy of the predictive models.

Enhancement of Surface Quality and Study on Material Removal Mechanism in Micro Ultrasonic Machining

Surface integrity, mechanical deformation, and thermal deformation are among the crucial error generation factors in tool-based micromachining the influence of which should be minimized. As a micromachining process, micro ultrasonic machining (micro-USM) must satisfy the above considerations. In micro-USM, material is removed by fine and free abrasive particles inside a fluid; hence, there is no direct contact between micro-tool and the workpiece. Furthermore, no thermal damage is induced into the machined surface. Therefore, this process can satisfy the requirements of minimum mechanical and thermal deformation as a tool-based micromachining process. However, usually a rather course surface with subsurface microcracks is generated by USM processes. As such, study on surface characteristics and improvement of surface quality in micro-USM is considered necessary in order to introduce this process as a mature micromachining process. In this paper, the effect of various process parameters on surface quality in micro-USM is studied. The parameters include static load, vibration amplitude, abrasive particle size, and slurry concentration. Machining experiments were conducted using a self-developed micro-USM system with the method of workpiece vibration and using a precision static load measurement system with high sampling rate. An average surface roughness as small as 24 nm was achieved through the investigations on machined surface quality which has not been reported in micro-USM process using the workpiece vibration method. Moreover, the effect of process parameters on dominant removal mechanisms is investigated.Copyright

An Investigation on Machining Power of EN-AC 48000 Aluminum Alloy Used in Automotive and Aerospace Industries

In this paper, the effect of machining parameters including cutting velocity, feed rate, and tool material on machining power of EN-AC 48000 aluminium alloy has been studied. A L27 Taguchis standard orthogonal array has been applied as experimental design to investigate the effect of the factors and their interaction. Twenty seven machining tests have been accomplished with two random repetitions, resulting in fifty four experiments. EN-AC 48000 is an important alloy in automotive and aerospace industries. Machining of this alloy is of vital importance due to build-up edge and tool wear. Machining power is an essential parameter affecting the tool life, dimensional accuracy, and cutting efficiency. Three types of cutting tools including coated carbide (CD 1810), uncoated carbide (H10), and polycrystalline diamond (CD10) have been used in this study. Statistical analysis has been employed to study the effect of factors and their interactions using ANOVA analysis. Moreover, optimal factor levels have been presented using signal to noise ratio (S/N) analysis. Also, regression model have been provided to predict the machining power. Finally, the results of confirmation tests have been presented to verify and compare the adequacy of the predictive models.

STUDY OF THE EFFECT OF LUBRICANT EMULSION PERCENTAGE AND TOOL MATERIAL ON SURFACE ROUGHNESS IN MACHINING OF EN AC 48000 ALLOY

In this paper, the effect of machining parameters, namely, lubricant emulsion percentage and tool material on surface roughness has been studied in machining process of EN‐AC 48000 aluminum alloy. EN‐AC 48000 aluminum alloy is an important alloy in industries. Machining of this alloy is of vital importance due to built‐up edge and tool wear. A L9 Taguchi standard orthogonal array has been applied as experimental design to investigate the effect of the factors and their interaction. Nine machining tests have been carried out with three random replications resulting in 27 experiments. Three type of cutting tools including coated carbide (CD1810), uncoated carbide (H10), and polycrystalline diamond (CD10) have been used in this research. Emulsion percentage of lubricant is selected at three levels including 3%, 5% and 10%. Statistical analysis has been employed to study the effect of factors and their interactions using ANOVA method. Moreover, the optimal factors level has been achieved through signal to noi...