Development of Laser and Electrochemical Machining Based on Internal Total Reflection

The behavior of wire electrochemical discharge machining of Al2O3 particle-reinforced aluminum alloy 6061 was studied. The effects of machining voltage, current, pulse duration, and electrolyte concentration, on material removal rate (MRR) were evaluated in the light of the contribution of the electrical discharge machining (EDM) and electrochemical machining (ECM) actions. The relative strength of the EDM and ECM activities in the machining process under different conditions was studied with the aid of the voltage waveforms. It was found that the conditions of high current or high concentrations of electrolyte would promote the ECM activity and result in a high MRR. The relative importance of the various cutting parameters on MRR was established using orthogonal analysis. The results suggest that to achieve the highest MRR, the applied current is the most influential factor among current, pulse duration and electrolyte concentration. This outcome is supported by experimental results and is explained in terms of the surface area of the matrix phase and the spark gap size.

High-efficiency and stable laser transmission for laser and electrochemical machining

Electrochemical machining (ECM) has an advantage of no tool wear. On the other side, it is difficult to carry out micro machining in ECM, because the electrode gap in ECM is large. In this paper, electrochemical micro machining with the developed electrode gap control system is demonstrated. The narrow gaps make the control of the process much more complex than normal ECM. Preliminary ECM experiments are carried out in order to investigate a proper condition of machining process. Small hole is machined by using a 0.2mm Ni rod. Drilling time and electrode gap is measured. An optimum machining condition of ECM is determined in terms of machining voltage, machining pulse length, amplitude of electrode for flushing out a contamination, and electrolyte concentration. After preliminary ECM experiments, three-dimensional micro machining is carried out under the optimum condition. First, prismatic electrode whose base is 200μm square is machined by ECM. Next, three-dimensional micro machining is carried out by scanning the prismatic electrode. Three-dimensional shape that is sub-millimeter order is successfully machined.

Electric discharge machining of Al–SiC metal matrix composites using rotary tube electrode

Machining of low machinable non conducting engineering materials like borosilicate glass has imposed challenges in the manufacturing of micro devices like microfluidics, MEMS etc. Electrochemical discharge machining (ECDM), a hybrid processes of electric discharge machining (EDM) and electro chemical machining (ECM), emerging as a potential method to address the low machinability problems. In the present work the influence of helical tungsten carbide tools of varying diameter assisted with high speed tool rotation was adopted to improve machining performance in terms of on the material removal rate (MRR), heat affected zone (HAZ), radial over cut (ROC), tool wear rate (TWR) and depth of machining (DOM). It was found that the hydrodynamic region was more predominant with tool diameters 600 μm, 700 μm and at 2,500 rpm and resulted to a low machining depth. Smaller diameter tools assisted with rotational was found significant influence on the machining responses.

Experimental investigation on the machining performance of honeycomb seal structures by using electrochemical discharge machining

Electrochemical discharge machining (ECDM) is a micro-machining hybrid technique that utilizes electrical discharge and electrochemical machining principles. However, the issue of insufficient electrolyte in the hydrodynamic region hinders the continuation of the machining action. Although ultrasonic tool vibrations have been used to overcome this problem to some extent, the excessive mechanical energy produced by high-amplitude tool vibration may lead to surface crack formations. As a result, the present work employs two flushing improvement methods, namely the ultrasonic vibrations and magnetic filed assistances, in the ECDM process. A comparative study has been performed to identify the effect of the magnetic field on discharge quality. The material removal rate and depth of penetration were increased by 11% and 24%, respectively, and the observed reduction in hole overcut and taper angle was around 35% and 50%, respectively. Optical microscope images quantified improvement in dimensional accuracy and decreased HAZ area.

Many advanced machining processes have higher initial investment, maintenance and tooling costs. In these circumstances micro electrochemical machining [µECM] processes meet the requirements with better efficiency and economy. The micro electrochemical machining process parameter such as electrolyte concentration, machine voltage, and pulse on time and duty factor are optimized with considerations of the multiple performance characteristics such as material removal rate (MRR) and overcut. Increase in electrolyte concentration considerably improves MRR but yields a poorer over cut. Increased machine voltage serves to increase both MRR and over cut significantly. Increased pulse on time and duty factor did not have notable impact on MRR and overcut. Less concentration of sodium chloride [NaCl] is sufficient for machining compared with sodium nitrate [NaNO3]. Higher MRR and better over cut are achieved with sodium chloride and moreover it is more economical than sodium nitrate.

Material wear of the tool electrode and metal workpiece in electrochemical discharge machining

Electrochemical machining (ECM) is one of nonconventional machining process used to operation the most harsh materials that difficult to operate in conventional machining. This search has been used to study impact of different parameters on material removal rate (MRR) and to improve the MRR. The workpiece material in this search is stainless steel 316L, tool material from copper and NaCl (10, 25, 50) g/l was used as electrolyte. Through the experiments noted that the MRR increasing at increased current from (50 to 200) the increasing in MRR reach to 57.60%, also MRR increasing at increasing electrolyte concentration from (10 to 50) g/l increasing in MRR (reach) to 75.17 % and MRR decreasing at increased gap size from (0.5 to 1.5) mm the decreasing in MRR reach to 39.2 %. To predict the values of MRR and to get optimization, artificial neural network was used to get minimum mean squared error (MSE) and minimum average percentage error. In network, separated some values to training set and the remaining for testing set and it was noted that the predicated and experimental values are very close to each other.

Experimental investigation of rotary ultrasonic face milling on red granite: A comparison with conventional grinding

Machining of Carbon Epoxy Composite using High Speed Electrochemical Discharge Machining

As semiconductor devices become smaller as well as better in performance with the improvement done in device level, packaging technology has also attracted much attention. Especially, flip-chip packaging technology which connects between chips by making micro-bumps on the land position has more advantages than the wire bonding packaging technology which connects chip and substrate using wire. In order to make micro-bumps, bumping process which deposits solder ball or solder paste through the holes in bumping mask is used. Therefore hole size uniformity of bumping mask is the key technology for high accurate bumping process. Usually bumping mask is fabricated by several methods such as electroforming, laser machining and chemical wet etching. But they have several limitations, respectively. Electroforming is an expensive process due to high cost of Ni which is a main component. Laser machining process also has a cost and process time issues when it comes to high density holes in large area because it makes hole on the substrate one by one directly with laser beam. Lastly although chemical wet etching process has good metal removal rate, the surface roughness after etching is high and hard to control etching process. In order to improve the limitations of conventional machining methods, we introduced Through-Mask Electrochemical Micro Machining (TMEMM) process. TMEMM process is originated from Electrochemical Machining (ECM) which uses electrochemical reaction at the interface between metal and electrolyte that makes it possible to fabricate smooth surface. TMEMM process uses electrochemical reaction as same with ECM, but resist patterning process is added to make resist pattern on substrate. By using resist pattern as a mask layer, only exposed area to electrolyte is dissolved selectively. Through this process, many patterns in large area can be etched at the same time. In this study, we optimized TMEMM process to fabricate bumping mask by controlling the process parameters. During optimization we had introduced a new TMEMM process design. In this process, electrolyte is circulated by pump system. The temperature of the electrolyte was kept constant with the help of refrigerated circulating bath. To make hole shaped resist pattern on the stainless steel substrate in large area, dry-film resist (DFR, HW440, Hitachi, Japan) was used. 400 x 400 mm DFR patterned stainless steel substrate was used as an anode, and Cu plate was used as a cathode. Pulse current was used with different current value, pulse on/off time and duty cycle. Phosphoric acid (H3PO4, 86 Vol%) was used as an electrolyte. The effect of temperature of electrolyte, distance and flow rate of electrolyte between electrodes, cathode material and insulation shield to prevent edge effect are investigated in this study. After TMEMM process, resist pattern on the stainless steel substrate was removed by dipping in 3M NaOH solution for 3 min. To analyze the uniformity of fabricated holes and surface quality of the wall of hole, Optical Microscope (L-150A, Nikon, Japan) and Field Emission Scanning Electron Microscope (FE-SEM, MIRA3, TESCAN, Czech) were used and we used coefficient of variation (CV) value as an indicator of uniformity. As a result, we fabricated the bumping mask which has 250.6 µm of average hole diameter with 2.8% of CV value and smooth surface.

Electrochemical machining (ECM) using tube electrodes is an effective approach for the rough machining of turbo engine blisks. The uniformity of the channel allowance decisively influences the accuracy of subsequent ECM precision for the blisk. A voltage regulation strategy to minimize allowance differences in the ECM is proposed. Simulation and experimental investigations are performed to determine the relationships between the channel width and the applied voltage. Comparative experiments using the conventional constant voltage method and the proposed voltage regulation method are performed. The experimental results show that the allowance differences on the back and basin surfaces of the blade are reduced by 47.81% and 51.57%, respectively, using the proposed method. Thus, the experimental results verify that the voltage regulation strategy is effective for the ECM of blisk channels.

Manufacturing engineers are facing new challenges during machining of electrically nonconducting or partially conducting materials such as glass, quartz, ceramics, and composites. Traveling wire electrochemical spark machining (TW-ECSM), a largely unknown technology, has been applied successfully for cutting these types of materials. However, hardly any theoretical work has been reported related to machining performance of TW-ECSM process. The present work is an attempt in this direction. In the present work, a 3-D finite element transient thermal model has been developed to estimate the temperature field and material removal rate (MRR) due to Gaussian distributed input heat flux of a spark during TW-ECSM. First, the developed code calculates the temperature field in the workpiece and then MRR is calculated using this temperature field. The calculated MRR has been compared with the experimental MRR for verifying the approach. Computational experiments have been performed for the determination of energy partition and spark radius of a single spark. The effects of various process parameters such as energy partition, duty factor, spark radius, and ejection efficiency on MRR have been reported. It has been found that MRR increases with increase in energy partition, duty factor, and ejection efficiency but decreases with increase in spark radius.