This study investigates the effects of electro-discharge parameters on the surface integrity in small-hole drilling. Discharge current, pulse on-time and pulse off-time were chosen as variable parameters. The gap voltage, dielectric flushing pressure, electrode rotation, electrode polarity and capacitance were taken as constant. Material removal rate, surface roughness, average white layer thickness, overcut and taper were taken as outputs for this study. Experiments were performed on DIN 1.2080 (X210Cr12) cold working tool steel, and ∅2 mm single-hole brass electrodes were used. The experimental results indicate that a compromise solution is required in selection of the electrical discharge machining parameters (i.e. discharge current, pulse on-time and pulse off-time) to maintain machining stability (melting–evaporation and removal of debris). As the stability is maintained during the process, dimensional accuracy increases and a better finish can be obtained with a reasonable machining time.

In this article, the effect of abrasive types on the abrasive flow machining process was investigated. Four groups of abrasive media were prepared with different types of abrasives: SiC, AL 2 O 3 , B 4 C and Garnet. An experimental study was performed on DIN 1.2379 tool steel. The specimens were cut using wire electrical discharge machining and finished with the abrasive flow machining process. The results show that the white layer that formed during wire electrical discharge machining was successfully removed by abrasive flow machining in a few cycles. Although the surface roughness improves with similar trends for all media groups, the results show that the media prepared with B 4 C and SiC have more surface improvement than the Al 2 O 3 and Garnet ones. The resulting average surface roughness (R a) values are comparable to the surface quality of those obtained from lapping and super-finishing. The material removal is directly related to the hardness of the abrasive.

Abrasive flow machining (AFM) is a manufacturing technique that uses the flow of a pressurized abrasive media to remove workpiece material. In comparison with other polishing technique, AFM is very efficient, suitable for the finishing of complex inner surfaces. In this paper, the effect of workpiece hardness on the AFM process has been investigated. An experimental study was carried out on AISI D2 tool steel hardened to 31, 45 and 55 HRC. The specimens were cut by using wire electro discharge machining (WEDM) and then finished with AFM. The results show that the white layer formed during WEDM is successfully removed by AFM in a few cycles. Although the surface quality is improved by AFM for all hardness groups, the results show that harder materials have more surface improvement than the softer ones.

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This study presents an experimental investigation of small hole electrical discharge machining of Al-Mg-Ti alloys. A series of drilling operations were carried out for exploring the effect of magnesium content. Holes of 2 mm diameter and 15 mm depth were drilled using tubular single-hole rotary brass electrodes. The rates of material removal and electrode wear, surface roughness, overcut, average recast layer thickness, taper height and angle were studied for Al-Mg-Ti alloys contain 2%, 4%, 6%, 8%, 10%, 12%, and 14% Mg. The results show that the material removal rate is increasing with increasing Mg content while the rate of electrode wear is almost unchanged. Due to decreasing the melting temperature of the Al-Mg-Ti alloy with increasing Mg content, more metal melts and vaporizes during electrical discharge machining drilling. Therefore, more overcut and taper, thicker white layer, and rougher surfaces were measured for higher Mg content.

Selection of appropriate operating conditions is an important attribute to pay attention for in electrical discharge machining (EDM) of steel parts. The achievement of EDM process is affected by many input parameters; therefore, the computational relations between the output responses and controllable input parameters must be known. However, the proper selection of these parameters is a complex task and it is generally made with the help of sophisticated numerical models. This study investigates the capacity of Adaptive Nero-Fuzzy Inference System (ANFIS), genetic expression programming (GEP) and artificial neural networks (ANN) in the prediction of EDM performance parameters. The datasets used in modelling study were taken from experimental study. According to the results of estimating the parameters of all models in the comparison in terms of statistical performance is sufficient, but observed that ANFIS model is slightly better than the other models.

Blanking operation is widely used to cut sheet or plates by a shearing process between punch and die. The process of shearing and the conditions of the sheared surface are influenced by the punch, the die, the speed of punching, the clearance between the punch and the die. In this study, effects of high speed blanking on surface quality and corrosion properties of mild steel St37 shear surface have been investigated. The work presented in this paper aims at evaluating the shear surface quality improvements of the St37 resulting from the use of high energy rate forging machine. The appraisal is based on criteria related to surface accuracy and corrosion resistance characterization. For this purpose, St37 mild steels were cut using three different punch speeds hydraulic presses at nearly quasistatic, conventional mechanical presses at low punch velocity (0.2 m/s) and high energy rate forging machine at high punch velocity (10 m/s), for different die clearances (4.5%-6% of sheet thickness). After accelerated corrosion tests, blanks were performed in conjunction with scanning electron microscopy technique to study the cutting process of the blanks at room temperature. In fact, by using high energy rate forging machine, a reduction of more than 25% of the surface roughness (Ra) was realized and better resistance to stress corrosion cracking and pitting corrosion was noticed. It was observed that the corrosion resistance of the high energy rate forging-cut specimen was better than that of the hydraulic-cut and mechanical-cut specimens.

ÖZETBu çalışmada, DIN 1,2379 kalıp çeliğine, tek delikli pirinç elektrotla, içerisinde farklı miktarlarda oksijen çözünmüş soğutma sıvısı kullanılarak elektro erozyon ile delik delme (EEDD) işlemi uygulanmıştır. Çalışmada elektro erozyon parametreleri sabit tutulmuş ve çözünmüş oksijenin EEDD performans parametreleri; işleme hızı, elektrot aşınması, yüzey pürüzlülüğü, beyaz katman tabakası, çap büyümesi ve çıkışta konikleşme üzerine etkileri incelenmiştir. Soğutma sıvısındaki çözünen oksijen miktarının artışı, elektro erozyon işleminin performansını arttırmıştır. İşleme zamanını % 20 iyileşme ile hızlanmış, yüzey pürüzlülük değeri R a 4,5 µm seviyelerinden 2,4 µm seviyelerine düşmüş, elektro erozyon ile işlemenin en olumsuz sonucu olarak bilinen beyaz katman tabakası kalınlığı yarıya düşürülmüş ve geometrik toleranslarda da önemli oranlarda iyileşmeler sağlanmıştır.Anahtar Kelimeler: Elektro erozyon ile delik delme, elektro erozyon işleme, oksijen çözünümü INVESTIGATION OF THE EFFECTS OF THE DISSOLVED OXYGEN IN THE COOLANT ON THE HOLE GEOMETRIES DRILLED BY ELECTRO EROSION ABSTRACTIn this study, electro discharge hole drilling processes is applied to the DIN 1.2379 tool steel by using single channel brass electrode and coolant which possess various amount of dissolved oxygen. In the study the electro erosion parameters kept constant and the effect of the dissolved oxygen on the performance parameters such as machining speed, electrode wear, surface roughness, white layer thickness, overcut in diameter and taper at the tip was examined. The increase of dissolved oxygen in the coolant improved performance parameters. Machining time is improved in 20%, surface roughness value R a is improved from 4.5 µm to 2.4 µm level, the unfavourable result of electro erosion machining, white layer thickness is decreased in half and some other improvement is obtained in dimensional tolerances.